Patent Publication Number: US-2004049288-A1

Title: Prosthesis for internal peritoneal dialysis and method of providing peritoneal dialysis

Description:
SPECIFICATION  
     [0001] This application is a Continuation-In-Part of U.S. patent application Ser. No. 09/833,286, filed Apr. 12, 2001, and entitled “Prosthesis for Internal Peritoneal Dialysis and Method of Providing Peritoneal Dialysis”; which is a Continuation-In-Part of U.S. patent application Ser. No. 09/693,591, filed Oct. 20, 2000, and entitled “Prosthesis for Continuous Internal Peritoneal Dialysis and Continuous Method of Providing Peritoneal Dialysis.” 
    
    
     
       FIELD OF THE INVENTION  
       [0002] This invention relates to generally to prosthesis for continuous internal peritoneal dialysis and a continuous method of carrying out peritoneal dialysis. More specifically, this invention relates to artificial kidneys, and more specifically to artificial kidneys implantable within a person&#39;s body with the intent that the patient be free from dialysis and transplantation. The artificial kidneys of this invention employ the normal operation of the person&#39;s body (i.e., breathing cycle of the person) to cause the flow of fluid within the prosthesis for the removal of toxic substances or other fluids from the person&#39;s body. For the treatment of edema states that are refractory to treatment with diuretics the dialysate can be a selected hypertonic solution for removing excess fluids; principally water.  
       BACKGROUND OF THE INVENTION  
       [0003] The dialysis art is a highly developed one; providing a variety of teachings for dialyzing a patient.  
       [0004] In accordance with a related dialysis procedure (e.g., hemodialysis) for purifying blood in a patient experiencing kidney failure, the contaminated blood is directed from a blood vessel of the patient&#39;s arm through a dialyzing membrane located extracorporeally of the body, in which the blood gives up its impurities to the dialyzing fluid. The purified blood is then directed back into the patient&#39;s body through another blood vessel. A representative disclosure of a system for use in purifying arterial blood and providing a venous return is disclosed in U.S. Pat. No. 3,579,441, issued to Brown.  
       [0005] The dialysis art also suggests the use of related peritoneal dialysis systems, wherein a dialysate is introduced directly into the abdomen of the patient and functions to receive impurities from the blood at the abdominal capillaries, and then is mechanically removed from the body. Representative peritoneal dialysis systems of this type are disclosed in U.S. Pat. No. 4,681,564 (Landreneau); U.S. Pat. No. 4,655,762 (Rogers); U.S. Pat. No. 4,586,920 (Peabody) and U.S. Pat. No. 4,437,856 (Valli).  
       [0006] All of the related art systems known to applicants suffer from one or more disadvantages. For example, a number of prior art systems require that the patient be connected, e.g., “hooked-up”, to a dialysis machine. This renders the patient immobile during treatment, is expensive to administer, and subjects the patient to a high risk of infection, and even death. Patients are protein restricted, because protein yields toxic degradation products (e.g., nitrogenous wastes) largely responsible for uremia, the state of being in kidney failure. Toxic levels of potassium may also result from the treatment. Moreover, chronic contact of the peritoneum with hypertonic dialysate solutions often creates chronic peritonitis, which is a painful, dangerous condition that interferes with the peritoneal dialysis process.  
       [0007] The absorption of dialysate into the bloodstream interferes with the peritoneum dialysate&#39;s ability to do its job of pulling in fluids. Therefore, peritoneal dialysis relies physiologically on the fact that the dialysis fluid in the abdominal cavity is more viscous or thicker than blood. In other words, the dialysis fluid has a higher osmolality or chemical potential than the bloodstream. This difference in potential causes water and other molecules known to those skilled in the art to diffuse into the abdomen via the semi-permeable membranes of the peritoneum and mesenteric parietes which line the abdominal cavity.  
       [0008] Additionally, all previous modes of dialysis have been essentially intermittent, rather than continuous; resulting in a variety of disturbances to the body&#39;s equilibrium. Patients become either over-hydrated or under-hydrated due to the intermittent process of adding and removing fluids. The systems can not maintain proper blood volume and chemical balance beyond the few hours following the treatment. The treatments sap the patient&#39;s energy and sense of well-being, making the patient look and feel chronically ill, and critically affecting the patient&#39;s lifestyle, happiness and longevity.  
       [0009] With respect to transplantation, the high cost and risks are well known. A match for the patient must be found, which may take years. If a kidney is found, and the patient is still strong enough to receive it, then there is no guarantee that the kidney will be accepted. The patient&#39;s immune system may recognize a kidney transplanted from another as foreign matter and act to combat and reject this perceived invasion. Anti-rejection medication, such as azathioprine, cyclosporine and steroids help to prevent rejection. However, anti-rejection medicines have a large number of side effects. If rejection occurs, treatment is available to possibly reverse the episode, but at the cost of more medication and side effects. With kidney transplantation, about one third of the patients do very well, about one third remain chronically ill, and about one third of the patients die within five years.  
       [0010] A need clearly exists for an artificial kidney, or prosthesis, that is lower in cost than existing systems, that can be utilized with a minimum of risk to the patient, that provides greater freedom of movement for the patient and that allows for the continuous formation of urine as in a normal functioning kidney. Therefore, it would be beneficial to provide a continuous internal peritoneal dialysis prosthesis and method. It would also be beneficial to provide a continuous internal peritoneal dialysis prosthesis and method which employs the normal breathing pattern of the patient to affect the dialysis operation, which is simple in operation and requires relatively few moving parts.  
       [0011] To applicant&#39;s knowledge, prior to this invention, there has been no artificial kidney that is implantable in the body to provide any of the functions normally provided by a healthy kidney. It is to such artificial kidneys that the present invention is directed.  
       SUMMARY OF THE INVENTION  
       [0012] This invention includes a continuous internal peritoneal dialysis prosthesis and method employing an abdominal sac including a dialysate therein, the abdominal sac being adapted to be retained in the abdominal region of a person&#39;s body for receiving unconcentrated urine through the walls of the sac without permitting dialysate to exit from the sac through the walls. The abdominal sac communicates the unconcentrated urine through a section of the patient&#39;s bowel via at least one conduit that extends through the section of bowel. A region of the conduit within the section of the patient&#39;s bowel includes apertures therein for communicating the unconcentrated urine in the conduit with walls of the section of bowel; thereby employing the natural function of the bowel to concentrate the urine.  
       [0013] In another preferred embodiment, this invention includes a continuous internal peritoneal dialysis prosthesis and method employing an abdominal sac, a fluid guide conduit and a conduit extension. The abdominal sac is adapted to include a dialysate therein. The abdominal sac includes a semi-permeable membrane outer wall, and is adapted to be retained in the abdominal region of a patient&#39;s body with the semi-permeable membrane outer wall being in communication with unconcentrated urine in the abdominal region for receiving unconcentrated urine through the semi-permeable membrane outer wall without permitting dialysate to exit through the outer wall. The fluid guide conduit is adapted to receive the unconcentrated urine and dialysate from the abdominal sac and to communicate the dialysate back into the abdominal sac for recirculation. The conduit extension extends from the fluid guide conduit and is adapted to receive the unconcentrated urine from the fluid guide conduit. The conduit extension is also adapted to extend into and terminate in a section of the patient&#39;s bowel separated from the patient&#39;s GI tract to communicate the unconcentrated urine in the conduit extension with the section of bowel for concentrating the urine within the section of bowel.  
       [0014] A continuous internal peritoneal dialysis method of this invention includes containing unconcentrated urine in the abdominal region of a patient, and directing the contained unconcentrated urine into a section of bowel in which the urine is concentrated for removal from the patient.  
       [0015] Further scope of applicability of the present invention will become apparent from the description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since the invention will become apparent to those skilled in the art from this detailed description.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016] The invention will be described in conjunction with the following drawings in which like reference numbers designate like elements, and wherein:  
     [0017]FIG. 1 is a front view of a continuous internal peritoneal dialysis prosthesis of a preferred embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0018]FIG. 2 is a front view of a continuous internal peritoneal dialysis prosthesis of another preferred embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0019]FIG. 3 is a front view of a continuous internal peritoneal dialysis prosthesis of a third embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0020]FIG. 4 is a front view of a continuous internal peritoneal dialysis prosthesis of a fourth embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0021]FIG. 5 is a front view of a continuous internal peritoneal dialysis prosthesis of a fifth embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0022]FIG. 6 is a front view of an internal peritoneal dialysis prosthesis of a sixth embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0023]FIG. 7 is a front view of a continuous internal peritoneal dialysis prosthesis of a seventh embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0024]FIG. 8 is a front view of a continuous internal peritoneal dialysis prosthesis of an eighth embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body;  
     [0025]FIG. 9 is a front partial view of an internal peritoneal dialysis prosthesis of a ninth preferred embodiment of the present invention showing parts thereof in section; and  
     [0026]FIG. 10 is a front view of a continuous internal peritoneal dialysis prosthesis of a tenth embodiment of the present invention showing parts thereof in section and being located in a person&#39;s body.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0027] Referring to FIG. 1, an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body is schematically illustrated at  10 . The prosthesis  10  includes an abdominal sac  12  in the abdominal region of the patient below diaphragm  14 , a thoracic pouch  16  in the thoracic region of a patient&#39;s body above the diaphragm  14 , a section of a patient&#39;s bowel  18  located within the abdominal section of the patient, and the patient&#39;s urinary bladder  20  connected to a downstream end of the bowel  18  through the patient&#39;s cecum or appendix  22  and distal right ureter  24 .  
     [0028] Still referring to FIG. 1, the abdominal sac  12  is connected to the thoracic pouch  16  through a conduit  26  including a one-way valve  28  therein. The one-way valve  28  permits fluid (e.g., unconcentrated urine) to flow only in the direction of arrow  30  from the abdominal sac  12  into the thoracic pouch  16 .  
     [0029] The abdominal sac  12  includes a semi-permeable outer wall  56  and an impermeable outer wall  58  separated by a semi-permeable window  34 . The region of the abdominal sac  12  defined by the semi-permeable outer wall  56  and the semi-permeable window  34  is a dialysis sac  32 . The impermeable outer wall  58  includes a first port  60  for receiving a proximal end of the conduit  26 . After the conduit  26  is in communication with the port  60 , the wall of the abdominal sac  12  is stitched about the conduit  26  to retain the conduit within the port  60 .  
     [0030] Still referring to FIG. 1, the prosthesis  10  includes a second conduit  36  that is connected to the thoracic pouch  16  and passes through the diaphragm  14  into and through a section of the patient&#39;s bowel  18 . The second conduit  36  also includes a one-way valve  38  to permit the unconcentrated urine to flow from the thoracic pouch  16  through the section of the patient&#39;s bowel  18  only in the direction of the arrow  40 .  
     [0031] As can be seen in FIG. 1, the patient&#39;s bowel  18  includes end sections sutured to the conduit  36  at both the entrance  42  to the bowel  18  and the exit  44  from the bowel  18 . The distal end  46  of the second conduit  36  extends through a lower end of the bowel  18  and is connected to the abdominal sac  12  to recycle the flow of unconcentrated (or partially concentrated) urine back into the abdominal sac  12 , as will be described in greater detail below. The distal end  46  is provided with a one-way valve  48  to permit the urine to flow only in the direction of arrow  49  from the patient&#39;s bowel  18  to the abdominal sac  12 .  
     [0032] As noted earlier, the abdominal sac  12  is formed of an impermeable membrane at outer wall  58 , and a semi-permeable membrane at outer wall  56  and window  34 . The semi-permeable outer wall  56  and window  34  define the dialysis sac  32  of the abdominal sac  12 . The semi-permeable membrane has pores or apertures (holes) that provide the membrane with a porosity which precludes dialysate within the dialysis sac  32  from escaping into the peritoneal region, but still permits unconcentrated urine within the peritoneal region to enter the dialysis sac  32  through osmotic pressure. The porosity of the semi-permeable window  34  also precludes dialysate within the dialysis sac  32  from filtering through the semi-permeable window  34  into the region of the abdominal sac  12  in communication with the conduits  26  and  36 . Therefore, in this example of the preferred embodiment, the dialysate is contained within the dialysis sac  32 . Because the abdominal sac  12  is required to function in an aqueous environment, it preferably is formed of a synthetic plastic material with some elastic qualities. However, the dialysis sac  32  should not be so elastic as to expand to an extent that permits the dialysate molecules or microstructures to exit from expanded pores of its walls.  
     [0033] In order to prevent the dialysis sac  32  from expanding to an extent that permits the dialysate to exit its walls, portions of the semi-permeable outer wall  56  and window  34  may alternatively be formed of an impermeable or substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom. Also, impermeable wall  58  could be made elastic and semi-permeable walls  56  and  34  inelastic.  
     [0034] In an exemplary environment of this invention, the dialysate exerts chemical potential to draw in unconcentrated urine (e.g., fluid wastes, electrolytes, etc.) via the adjacent peritoneum and mesenteric parieties. The dialysate can be a large inert molecule or microstructure, e.g., microspheres, such as a 50 micron polyelectrolyte or L-racemate of any giant inert molecule which cannot exit the sac. It should be understood that, in accordance with the broadest aspects of this invention, the specific dialysate employed does not constitute a limitation on the present invention. However, the particle size of the dialysate must be such that the dialysate does not escape through the semi-permeable membrane walls of the dialysis sac  32  during operation of the prosthesis  10 .  
     [0035] Ideally, the pores or apertures in the semi-permeable membrane should be about 10 microns non-expanded to about 20 microns expanded, while the dialysis molecule should have a nominal size in the range of 50 to 100 microns. Of course, these numerical values are disclosed for purposes of illustration only, and are not intended to limit the scope of the present invention.  
     [0036] The semi-permeable membrane can be made of any suitable synthetic plastic material, such as a Gortex-like cloth, and the dialysate can be made from a wide variety of molecules or microstructures well-known to those skilled in the art. The thoracic pouch  16 , first conduit  26 , second conduit  36  and impermeable outer wall  58  of the abdominal sac  12  are preferably made from silicon plastic, which is inert and does not cause peritoneal irritation.  
     [0037] In the preferred form of this invention, the dialysis sac  32  is positioned between the peritoneum and mesenteric parieties in the left lower quadrant of the abdomen to extract fluids (unconcentrated urine) via osmotic diffusion and ultra filtration by the same physiological principles that control regular peritoneal dialysis. The dialysis sac  32  swells with unconcentrated urine which then traverses the window  34  shared with the abdominal sac  12 . As shown in FIG. 1, the dialysate does not leave the dialysis sac  32  and therefore cannot be absorbed by the lymphatic system or irritate the peritoneum. The unconcentrated urine entering the dialysis sac  32  through the semi-permeable membrane and exiting through the window  34  will then be directed through the first conduit  26  and the one-way valve  28 , through the diaphragm  14  and into the thoracic pouch  16  by the internal body pumping mechanism based on relative pressure changes in the abdomen and thorax during the breathing cycle, as described later in this application. It should be understood that neither the conduit  26  nor the thoracic pouch  16  have any permeability, i.e., they are impermeable so as to preclude the escape of any unconcentrated urine therefrom.  
     [0038] As is shown in FIG. 1, the abdominal sac  12  and the thoracic pouch  16  communicate with subcutaneous access reservoirs  50  and  51 , respectively, each of which include an access section closely adjacent the patient&#39;s skin. The subcutaneous access reservoirs (SARs)  50  and  51 , permit the monitoring and testing of the urine in order to determine the effectiveness of the prosthesis. The subcutaneous access reservoirs  50  and  51  provide adjustments of urine flow and urine constituents by adding or subtracting dialysate to fit each patient&#39;s needs. The dialysate can be added or withdrawn from the subcutaneous access reservoirs  50  and  51  using a syringe or tube inserted through the patient&#39;s skin into the reservoirs.  
     [0039] The unconcentrated urine within the thoracic pouch  16  then passes through the second conduit  36  and one-way valve  38  therein to a section of the patient&#39;s bowel  18 . Movement of the unconcentrated urine from the thoracic pouch  16  through the second conduit  36  takes place by an internal pumping mechanism to be described in greater detail hereinafter. Suffice it to state at this time that the second conduit  36  traverses a relatively long segment of bowel that has been isolated from the rest of the bowel. The segment that preferably is selected includes the right colon and ileum, and is capable of 90% water reabsorption in the bowel, which translates to 10 to 20 liters of water per day.  
     [0040] The movement of the unconcentrated urine through the bowel  18  is a unique feature of the present invention. The second conduit  36 , which directs the unconcentrated urine into the segment of the patient&#39;s bowel  18  includes a series of relatively large holes (or apertures)  54 , e.g., one-half cm, so as to allow the unconcentrated urine within the conduit  36  to move into the bowel  18 , wherein the bowel  18  functions to reabsorb water, electrolytes and small molecules, resulting in the formation of concentrated urine. The bowel will not absorb large molecules, standard excretory wastes and other poisons, or even standard proteins. It should be noted that the jejunum is anastomosed to transverse colon to restore the integrity of the GI tract, and therefore, though the section patient&#39;s bowel  18  is isolated, its blood supply remains intact so as to permit it to function in this invention.  
     [0041] Some of the concentrated urine will traverse the appendix  22 , which has a one-way peristalsis to the bladder  20 , which appropriately excretes the concentrated urine based on the bladder&#39;s normal function. The remaining urine is returned through the distal end  46  of the conduit  36  to the abdominal sac  12  for recirculation and recleansing. This distal end  46  of the conduit  36  is impermeable to preclude the escape of any urine therefrom.  
     [0042] It is important to note that in this exemplary prosthesis of this preferred embodiment, there is no free dialysate in the peritoneal cavity; the dialysate being retained in the dialysate sac  32 . It is only in such a system that it is both safe and advantageous for there to be emphatic reabsorption.  
     [0043] In fact, it should be noted that in prior art peritoneal dialysis the reabsorption of dialysate and unconcentrated urine creates a major problem for two reasons. First, it interferes with the vary process of discarding this excessive fluid. Second, any system in which dialysate is reabsorbed causes two other problems, the first of which is that it interferes with the very difference in osmotic pressure needed for the whole process of diffusion and ultra filtration, and secondarily, even if the dialysate molecule is inert versus the sugar, salt or albumin used in standard dialysis, each of which causes its own special problems when reabsorbed by the lymphatic system, it creates a tremendous problem with oncotic pressure.  
     [0044] Therefore, it should be emphasized that the continuous internal peritoneal dialysis prosthesis and method of this preferred embodiment is highly advantageous because the dialysate itself is separate at all times from the peritoneal space and from lymphatic absorption. The fact that some partially concentrated urine is recycled in the present invention is also advantageous. In particular, this recycling of partially concentrated urine allows for further cleansing of nitrogenous wastes from the urine and is precisely the same thing that happens during urine formation in a kidney that is functioning normally.  
     [0045] It also should be noted that, in a manner identical to the functioning of a normal kidney, the lower the serum osmolality (the more liquids a patient consumes) the better the peritoneal system of this invention works. In particular, the greater the differential between the osmotic pressure in the dialysis sac  32  employed in this invention and the blood (serum osmolality) the more urine is made. Therefore, the patient employing the prosthesis of this invention is able to drink as much as he or she wants, unlike other dialysis patients, because his/her increased intake of water simply increases the performance of the prosthesis of this invention. This is a significant benefit of the present invention.  
     [0046] As noted earlier, when the unconcentrated urine is turned into concentrated urine within the section of the patient&#39;s bowel  18 , most of the concentrated urine will exit to the distal right ureter  24 , which can be attached to the cecum or appendix  22  when appropriate, and this concentrated urine, of course, would then go into the urinary bladder  20  to be expelled intermittently, just as in a normally functioning human patient.  
     [0047] It should be noted that the process is continuous and prevents sudden changes in volume and concentration of the blood&#39;s constituents. The continuous operation of the prosthesis of this invention relies upon the internal body pumping action of the disclosed system. This internal body pumping action is a variation of the internal body pump and systems disclosed in Applicant&#39;s U.S. Pat. No. 5,813,410. The entire subject matter of this latter patent is hereby incorporated by reference herein.  
     [0048] However, by way of explanation, the fluid is circulated through the prosthesis  10  of this invention by means of a body-operated pump, e.g., the abdominal sac  12  and thoracic pouch  16  serve as pumps operated by a patient&#39;s breathing pattern to cause the fluid to flow through the prosthesis. In particular, fluid flow within the prosthesis  10  is created by taking advantage of the normal function of a person&#39;s diaphragm  14  and the normal internal pressure relationships that exist between the thoracic cavity and the abdominal cavity of the person&#39;s body while a person is breathing. Specifically, during inspiration (inhaling) the diaphragm, which separates the thoracic and abdominal cavities, is forced to descend; thereby leading to an increase in the intra thoracic volume and a corresponding decrease in the intra thoracic pressure. Conversely, the volume of the abdominal cavity decreases and the pressure in that cavity increases. This action forces fluid from the abdominal sac  12  located in the abdominal cavity through conduit  26  and into the thoracic pouch  16  in the thoracic cavity. The flow from the abdominal sac  12  to the thoracic pouch  16  is limited to flowing through the conduit  26  only in the direction of arrow  30 , due to the arrangement of the one-way valve  28  in that conduit  26 .  
     [0049] Upon expiration (exhaling) the operation of the diaphragm is reversed. That is, the diaphragm is forced to rise; thereby leading to a decrease in the intra thoracic volume and the corresponding increase in the intra thoracic pressure. Conversely, during expiration, the volume of the abdominal cavity increases and the pressure in that cavity decreases. This action forces fluid from the thoracic pouch  16 , located in the thoracic cavity, preferably in the costo phrenic sulcus thereof, to flow through the conduit  36 , and into the section of the patient&#39;s bowel  18  for delivery into the urinary bladder  20  or back into the abdominal sac  12 . Fluid flow from the thoracic pouch  16  through the bowel section  18  is limited to flowing only in the direction of arrow  40 , due to the inclusion of the one-way valve  38  in the second conduit  36 . Likewise, fluid flow from the bowel section  18  to the abdominal sac  12  is limited to flowing only in the direction of arrow  49 , due to the inclusion of the one-way valve  48 .  
     [0050] As should be appreciated from the foregoing, in operation the unconcentrated urine which is directed into the dialysis sac  32  is continuously moved through the prosthesis  10  by the breathing cycle of a patient, as described. The unconcentrated urine directed through the second conduit  36  into the bowel section  18  is then processed by the bowel section to concentrate the urine for ultimate removal through the urinary bladder  20 .  
     [0051] If necessary, or desired, the pumping action provided by the breathing cycle of the patient can be augmented, or even supplanted, by another device, e.g., a mechanical or electrical pump implanted in the person&#39;s body in fluid communication with the loop of circulating fluid.  
     [0052] Referring to FIG. 2, there is shown at  62 , an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body in accordance with a second preferred embodiment of this invention, which is similar to the prosthesis  10  discussed above and illustrated in FIG. 1. As shown in FIG. 2, the prosthesis  62  includes an abdominal sac  64  in the abdominal region of the patient below diaphragm  14 , a thoracic pouch  16  in the thoracic region of the patient&#39;s body above the diaphragm  14 , a section of the patient&#39;s bowel  18  located within the abdominal section of the patient, and the patient&#39;s urinary bladder  20  connected to a downstream end of the bowel  18  through the patient&#39;s cecum or appendix  22  and distal right ureter  24 . The abdominal sac  64  is connected to the thoracic pouch  16  through a conduit  26 , including a one-way valve  28  therein. The one-way valve  28  permits fluid to flow only in the direction of arrow  30  from the abdominal sac  64  into the thoracic pouch  16 .  
     [0053] The prosthesis  62  includes a second conduit  36  having a proximal end  68  and a distal end  46 . This second conduit  36  is connected to the thoracic pouch  16  through its proximal end  68  and passes through the diaphragm  14  into and through a section of the patient&#39;s bowel  18 . The second conduit includes a one-way valve  38  at its proximal end  68  to permit the unconcentrated urine to flow from the thoracic pouch  16  through the section of the patient&#39;s bowel  18  only in the direction of arrow  40 . The distal end  46  of the second conduit  36  extends through a lower end of the bowel  18  and is connected to the abdominal sac  64  to recycle the flow of unconcentrated (or partially concentrated) urine back into the abdominal sac  64 . The distal end  46  is provided with a one-way valve  48  to permit the urine to flow only in the direction of arrow  49  from the patient&#39;s bowel  18  to the abdominal sac  64 . The patient&#39;s bowel  18  is sutured to the conduit  36  at both the entrance  42  to the bowel  18  and the exit  44  from the bowel  18 .  
     [0054] As noted above, the prosthesis  62  shown in FIG. 2 is constructed similar to the prosthesis  10  shown in FIG. 1. However, in this embodiment, the dialysate is not contained only within a dialysis sac. In fact, the abdominal sac  64  does not include or share a window with a dialysis sac. In FIG. 2, the abdominal sac  64 , thoracic pouch  16  and conduits  26  and  36  provide a closed system for the dialysate, allowing the dialysate to cycle within the prosthesis  62 , but preventing the dialysate from leaving the prosthesis  62 .  
     [0055] The abdominal sac  64  is generally formed of a semi-permeable membrane having a porosity which precludes the dialysate within the abdominal sac  64  from escaping into the peritoneal region, but still permits unconcentrated urine within the peritoneal region to enter the abdominal sac  64  through osmotic pressure. Because the abdominal sac  64  is required to function in an aqueous environment, it preferably is formed of a synthetic plastic material with some elastic qualities (e.g., Gortex-like cloth). However, the abdominal sac  64  should not be so elastic as to expand to an extent that permits the dialysate molecules or microstructures to exit from expanded pores of its walls.  
     [0056] The abdominal sac  64  may be similar to the abdominal sac  12  shown in FIG. 1, but without the wall  34 . As with the abdominal sac  12  of FIG. 1, portions of the wall of the abdominal sac  64  may alternatively be formed of an impermeable or substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom.  
     [0057] As noted earlier, the section of the patient&#39;s bowel  18  is sutured to the conduit  36  at both the entrance  42  to the bowel  18  and the exit  44  from the bowel  18 , thereby enclosing a central region  66  of the conduit  36 . This central section  66  includes a semi-permeable wall so as to allow the unconcentrated urine within the central region of the second conduit  36  to move into the bowel  18 , wherein the bowel functions to reabsorb water, electrolytes and small molecules, resulting in concentrated urine. However, the semi-permeable wall prevents the dialysate from moving into the bowel, thus keeping the dialysate within the prosthesis  62 . It should be understood that neither the conduit  26 , the thoracic pouch  16 , nor the proximal end  68  of the conduit  36  have any permeability, i.e., they are impermeable so as to preclude the escape of any unconcentrated urine or dialysate therefrom.  
     [0058] As is shown in FIG. 2, the unconcentrated urine entering the abdominal sac  64  through the semi-permeable membrane, and the dialysate are directed through the first conduit  26  and the one-way valve  28 , through the diaphragm  14  and into the thoracic pouch  16  by the internal body pumping mechanism described above. The unconcentrated urine and dialysate within the thoracic pouch  16  then pass through the second conduit  36  and one-way valve  38  therein to a section of the patient&#39;s bowel  18 . Movement of the unconcentrated urine and dialysate from the thoracic pouch  16  through the second conduit  36  takes place by the internal body pumping mechanism described above. As mentioned above, the central region  66  of the second conduit  36 , which directs the unconcentrated urine and dialysate into the segment of the patient&#39;s bowel  18  is formed of a semi-permeable membrane so as to allow the unconcentrated urine within the conduit  36  to move into the bowel, wherein the bowel functions to reabsorb water, electrolytes and small molecules, resulting in concentrated urine. However, the semi-permeable membrane prevents the dialysate from leaving the second conduit  36 .  
     [0059] In a manner similar to the prosthesis shown in FIG. 1, some of the concentrated urine in FIG. 2 will traverse the appendix  22 , which has a one-way peristalsis to the bladder  20 , which appropriately excretes the concentrated urine based on the bladder&#39;s normal function. The remaining urine (unconcentrated and partially concentrated) is returned with the dialysate through the distal end  46  of the conduit  36  to the abdominal sac  64  for circulating and recleansing. Preferably, the distal end  46  of the conduit  36  is impermeable to preclude the escape of any urine and dialysate therefrom.  
     [0060] Typically in chronic peritoneal dialysis, the dialysate is introduced directly into the peritoneal space via a catheter and removed after it has drawn in urine. Introducing the dialysate into the peritoneal space presents problem with the chronic peritoneal dialysis procedure. Peritoneal irritation and chronic thickening caused by the dialysis leads to poor diffusion and ultra filtration. In addition, the dialysate in the peritoneal space can cause problems in the bloodstream (e.g., hypertonic sugar, hypertonic salt, increases in nitrogenous wastes, and problems in the bloodstream including bleeding and clotting disorders, poisoning various enzyme systems, antigen-antibody reactions, D-C, etc.).  
     [0061] The embodiments of the invention discussed above and illustrated in FIGS. 1 and 2 do not suffer from these problems because the dialysate cannot filter through the semi-permeable membrane. However, the embodiments of the invention discussed below allow for direct contact of the dialysate with the peritoneum. The continuous internal peritoneal dialysis prosthesis discussed below are of greater benefit when using a dialysate that cannot be absorbed by the lymphatic system or where there is minimal absorption of the dialysate without toxicity.  
     [0062] Referring to FIG. 3, an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body is schematically illustrated at  70 . The prosthesis  70  includes an abdominal sac  64  in the abdominal region of the patient below the diaphragm  14 , a thoracic pouch  16  in the thoracic region of the patient&#39;s body above the diaphragm  14 , a section of a patient&#39;s bowel  18  located within the abdominal region, conduits  26  and  36  connected between the abdominal sac  64  and the thoracic pouch  16 , and a semi-permeable membrane  72  enclosed within the bowel  18 . The abdominal sac  64 , thoracic pouch  16 , bowel  18 , and conduits  26  and  36  are similar to the like elements shown in FIG. 2. However, the conduits  26  and  36  include a series of relatively large holes  54  (e.g., one-half centimeter) that allow urine and dialysate to permeate therethrough, as will be described later.  
     [0063] The abdominal sac  64  may be similar to the abdominal sac  12  shown in FIG. 1, but without the wall  34 . As with the abdominal sac  12  of FIG. 1, portions of the abdominal sac  64  may alternatively be formed of an impermeable or substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom.  
     [0064] As can be seen in FIG. 3, the section of the patient&#39;s bowel  18  is sutured to the conduit  36  at both the entrance  42  to the bowel  18  and the exit  44  from the bowel  18 . The semi-permeable membrane  72  extends about the second conduit  36  within the bowel  18  and is attached to the second conduit  36  at both the entrance  74  to the membrane  72  and the exit  76  from the membrane  72 . The semi-permeable membrane  72  is preferably a synthetic plastic material with some elastic qualities having a porosity which precludes dialysate from filtering through the semi-permeable membrane, but permits unconcentrated urine to filter through the material.  
     [0065] In this embodiment, both the dialysate and unconcentrated urine are present in the peritoneal region. The abdominal sac  64  receives unconcentrated urine and dialysate via the relatively large holes  54  of the first conduit  26 . In addition, the abdominal sac  64  receives unconcentrated urine through sections of the wall of the abdominal sac  64  that are made of semi-permeable membrane.  
     [0066] The unconcentrated urine and dialysate entering the abdominal sac  64  is directed through the first conduit  26  and the one-way valve  28 , through the diaphragm  14  and into the thoracic pouch  16  by the internal body pumping mechanism described above. Unconcentrated urine and dialysate also flow from the peritoneum through the relatively large holes  54  into the first conduit  26 , and is directed toward the thoracic pouch  16 . The unconcentrated urine and dialysate within the thoracic pouch  16  then pass through the second conduit  36  and the one-way valve  38  therein to a section of the patient&#39;s bowel  18 . Movement of the unconcentrated urine and dialysate from the thoracic pouch  16  through the second conduit  36  takes place by the internal pumping mechanism described above, which may be assisted or supplemented with a pump. As noted above, the second conduit  36  which directs the unconcentrated urine and dialysate into the segment of the patient&#39;s bowel  18  includes a series of relatively large holes  54  so as to allow the unconcentrated urine and dialysate within the second conduit  36  to flow out of the conduit  36 . The semi-permeable membrane  72  that is within the bowel  18  has a porosity which precludes the dialysate that filtered through the holes  54  of the second conduit  36  from escaping into the bowel  18 , but still permits the unconcentrated urine to permeate into the bowel  18 , wherein the bowel  18  functions to reabsorb water, electrolytes and small molecules resulting in concentrated urine.  
     [0067] As noted earlier, when the unconcentrated urine is turned into concentrated urine within the section of the patient&#39;s bowel  18 , most of the concentrated urine will exit to the distal right ureter  24 , which can be attached to the cecum or appendix  22  when appropriate. The concentrated urine will then flow into the urinary bladder  20  to be expelled intermittently, just as in a normally functioning human patient. The dialysate and returning urine is returned through the distal end  46  of the conduit  36  to the abdominal sac  64  for recirculation and recycling. This distal end  46  of the conduit  36 , and the sections of the conduits  26  and  36  above the diaphragm  14  are impermeable to preclude the escape of any urine or dialysate therefrom.  
     [0068]FIG. 4 is still another embodiment of the invention wherein dialysate is in direct contact with the peritoneum. Referring to FIG. 4, an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body is schematically illustrated at  80  and is similar to the prosthesis is shown in FIG. 1. The prosthesis  80  includes an abdominal sac  82  in the abdominal region of the patient below diaphragm  14 , a thoracic pouch  16  in the thoracic region of the patient&#39;s body above the diaphragm  14 , a section of the patient&#39;s bowel  18  located within the abdominal section of the patient and a urinary bladder  20  connected to a downstream end of the bowel  18  through the patient&#39;s cecum or appendix  22  and distal right ureter  24 .  
     [0069] The abdominal sac  82  includes a semi-permeable outer wall  56  and an impermeable outer wall  58  separated by a semi-permeable window  86 . The region of the abdominal sac  82  defined by the semi-permeable outer wall  56  and the semi-permeable window  86  is a dialysis sac  84 . The semi-permeable outer wall  84  and window  86  are formed of a semi-permeable membrane as discussed in detail above. The abdominal sac  82 , dialysis sac  84 , thoracic pouch  16 , first conduit  26 , bowel  18  and second conduit  36  shown in FIG. 4 are substantially similar to the abdominal sac  12 , dialysis sac  32 , thoracic pouch  16 , first conduit  26 , bowel  18  and second conduit  36  shown in FIG. 1. However, instead of the distal end  46  of the second conduit  36  being formed of an impermeable material and connected to the abdominal pouch  12  (FIG. 1), the distal end  46  of FIG. 4 includes a series of relatively large holes  54  (e.g., one-half centimeter) and is connected to the semi-permeable outer wall  56  of the dialysis sac  84 .  
     [0070] The distal end  46  includes the holes  54  so as to allow unconcentrated urine and dialysate in the peritoneum to move into the conduit  36  and then into the dialysis sac  84 . The dialysate is contained within the distal end  46  of the conduit  36  and the dialysis sac  84  and does not flow through the remainder of the prosthesis  80 . The one-way valve  48  permits the unconcentrated and partially concentrated urine exiting from the second conduit  36  in the bowel  18  to travel towards the dialysis sac  84 , but does not allow fluid, including the dialysate, to enter the second conduit  36  in the bowel  18  from the distal end  46 .  
     [0071] In FIG. 4, unconcentrated urine flows from the abdominal sac  82  through the first conduit  26  and one-way valve  28  through the diaphragm  14  to the thoracic pouch  16 . The unconcentrated urine within the thoracic pouch  16  then passes through the diaphragm  14  and one-way valve  38  in the second conduit to the patient&#39;s bowel  18 . Movement of the urine through the prosthesis  10  takes place by the internal pumping mechanism described in detail above.  
     [0072] As noted earlier during the discussion of FIG. 1, the second conduit  36  of FIG. 4, which directs the unconcentrated urine into the segment of the patient&#39;s bowel  18 , includes a series of relatively large holes  54 . The holes  54  allow the unconcentrated urine within the conduit  36  to move into the bowel  18 , wherein the bowel  18  functions to reabsorb water, electrolytes and small molecules resulting in concentrated urine. Some of the concentrated urine will traverse the appendix  22  which has a one-way peristalsis to the bladder  20 , which appropriately excretes the concentrated urine based on the bladder&#39;s normal function. The remaining urine is returned through the distal end  46  of the conduit  36  (where it is mixed with unconcentrated urine and dialysate from the peritoneum) to the dialysis sac  84  for recirculation and recleansing.  
     [0073] In order to prevent the dialysis sac  84  from expanding to an extent that permits the dialysate to exit the walls, portions of the semi-permeable outer wall  56  and the semi-permeable window  86  may alternatively be formed of an impermeable or substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom. Also, the impermeable wall  58  could be made elastic and the semi-permeable wall  56  and window  86  made inelastic.  
     [0074] Although the conduits  26  and  36  are illustrated in the exemplary embodiments shown in FIGS.  1 - 4  as being separate conduits spaced apart from each other and extending through separate passages in the diaphragm  14 , it should be understood that, in a preferred construction, the conduits  26  and  36  are interconnected together and pass through only a single aperture in the diaphragm  14 . The spaced apart arrangement of the conduits  26  and  36  is shown in the drawings for purposes of clarity.  
     [0075] The operation of all of the embodied prostheses shown in FIGS.  1 - 4  is preferably continuous and relies upon the internal body pumping action of the disclosed systems. This internal body pumping action is described in relation to FIG. 1 and is substantially similar in operation for the other exemplary embodiments shown in FIGS.  2 - 4  as a skilled artesian would readily understand. The described internal body pumping action is a variation of the internal body pump and systems disclosed in Applicant&#39;s U.S. Pat. No. 5,813,410, the entire subject matter of which is incorporated by reference herein. In addition, for all of the exemplary embodiments, the pumping action provided by the breathing cycle of the patient can be augmented, or even supplanted, by another device (e.g., a mechanical or electrical pump implanted in the person&#39;s body in fluid communication with the loop of circulating fluid).  
     [0076] Referring to FIG. 5, a further and preferred exemplary continuous peritoneal dialysis prosthesis inserted within a person&#39;s body is schematically illustrated at  100 . The prosthesis  100  includes a thoracic pouch  16  in the thoracic region of the patient&#39;s body above the diaphragm  14 , a section of the patient&#39;s bowel  18  located within the abdominal region, conduits  26  and  36  communicating between the thoracic pouch  16  and the abdominal region, and a semi-permeable membrane  72  enclosed within the bowel  18 . The thoracic pouch  16 , bowel  18 , and conduits  26  and  36  are similar to the like elements shown in FIG. 3. However, this embodiment is different than the embodiment shown in FIG. 3 because this embodiment omits the abdominal sac disclosed in FIG. 3.  
     [0077] As can be seen in FIG. 5, the section of the patient&#39;s bowel  18  is sutured to the conduit  36  at both the entrance  42  to the bowel  18  and the exit  44  from the bowel  18 . The semi-permeable membrane  72  extends about the second conduit  36  within the bowel  18  and is attached to the second conduit  36  at both the entrance  74  to the membrane  72  and the exit  76  from the membrane  72 . The semi-permeable membrane  72  is preferably a synthetic plastic material with some elastic qualities having a porosity which precludes dialysate from filtering through the semi-permeable membrane, but permits unconcentrated urine to filter through the material. The conduits  26  and  36  include a series of relatively large holes  54  (e.g., about one-half centimeter) that allow urine and dialysate to permeate therethrough as will described later.  
     [0078] In this embodiment, both the dialysate and unconcentrated urine are present in the peritoneal region. The first conduit receives unconcentrated urine and dialysate via the relatively large holes  54  and distal opening  102 . The unconcentrated urine and dialysate is directed through the first conduit  26  and the one-way valve  28 , through the diaphragm  14  and into the thoracic pouch  16  by the internal body pumping mechanism described above. The unconcentrated urine and dialysate within the thoracic pouch  16  then pass through the second conduit  36  and the one-way valve  38  therein to a section of the patient&#39;s bowel  18 . Movement of the unconcentrated urine and dialysate from the thoracic pouch  16  through the second conduit  36  takes place by the internal pumping mechanism described above, which may be assisted or supplemented with a pump. In particular, the thoracic pump  16  serves as a pump influenced by a patient&#39;s breathing pattern to cause the unconcentrated urine and dialysate to flow through the prosthesis  100 .  
     [0079] The prosthesis  100  omits the abdominal sac disclosed in the other embodiments of this invention and generally employs the peritoneal region as the “sac” region for retaining dialysate and unconcentrated urine. Accordingly, like the prosthesis shown above in FIGS. 3 and 4, the prosthesis  100  is of greatest benefit when using a dialysate that cannot be absorbed by the lymphatic system or where there is minimal absorption of the dialysate without toxicity (e.g., absorbable albumin). Because the dialysate is not contained within a separate abdominal sac, it is preferred that dialysate is added to the prosthesis (e.g., about 1 liter every few days) to ensure that a sufficient amount of dialysate is retained within the peritoneal region.  
     [0080] It should be apparent that the unconcentrated urine and dialysate does not flow through the prosthesis  100  as efficiently as the fluids flow through the embodiments discussed above that include both an abdominal sac and a thoracic pouch. Without an abdominal sac, the prosthesis does not form a closed loop and the thoracic pouch is relied upon to cause the fluid to flow through the prosthesis without the aid of an abdominal sac, as described above. Accordingly, this embodiment may be better suited for a patient that has only partial kidney failure.  
     [0081] As noted above, the second conduit  36  which directs the unconcentrated urine and dialysate into a segment of the patient&#39;s bowel  18  includes a series of relatively large holes  54  so as to allow the unconcentrated urine and dialysate within the second conduit  36  to flow out of the conduit. The semi-permeable membrane  72  that is within the bowel has a porosity which precludes the dialysate that filters through the holes  54  of the second conduit  36  from escaping into the bowel  18 , but still permits the unconcentrated urine to permeate into the bowel  18 , wherein the bowel functions to reabsorb water, electrolytes and small molecules resulting in concentrated urine.  
     [0082] Still referring to FIG. 5, it should be noted that in lieu of the relatively large holes  54  located in the second conduit  36  and the semi-permeable membrane  72  located within the bowel  18 , the conduit  36  within the bowel  18  can be constructed like the central region  66  of the conduit  36  shown in FIG. 2. That is, in FIG. 5, the conduit  36  within the bowel  18  can be formed of the semi-permeable membrane.  
     [0083] As noted earlier, when the unconcentrated urine is turned into concentrated urine within the section of the patient&#39;s bowel  18 , most of the concentrated urine will exit to the distal right ureter  24  which can be attached to the cecum or appendix  22  when appropriate. The concentrated urine will then flow into the urinary bladder  20  to be expelled intermediately, just as in a normally functioning human person. The dialysate and returning urine is returned through the distal end  46  of the conduit  36  into the abdominal region. Preferably, the distal end  46  of the second conduit  36  should either be of a very small diameter, or employ a moderate pressure one-way valve  48  therein to control the flow of fluid into the peritoneal space in a manner that allows adequate time for the bowel to absorb water from the unconcentrated urine passing therethrough, but not such as to prevent flow of unconcentrated or partially concentrated urine back into the peritoneal space for lymphatic reabsorption and recycling through the entire system.  
     [0084] It should be noted that the thoracic pouch  16  preferably communicates with a subcutaneous access reservoir  50 , which includes an access section closely adjacent the patient&#39;s skin. The subcutaneous access reservoir  50  permits the monitoring and testing of the urine in order to determine the effectiveness of the prosthesis. The reservoir  50  also provides adjustments of urine flow and urine constituent by adding or subtracting dialysate to fit each patient&#39;s needs. The dialysate can be added or withdrawn from the subcutaneous access reservoir  50  using a syringe or tube inserted through the patient&#39;s skin into the reservoir.  
     [0085] Referring to FIG. 6, there is shown at  110  an exemplary internal peritoneal dialysis prosthesis inserted within a patient&#39;s body in accordance with yet still another preferred embodiment of this invention. As shown in FIG. 6, the prosthesis  110  includes an abdominal sac  112  in the abdominal region of the patient below the diaphragm. The abdominal sac  112  includes an extension that expands into a section of the patient&#39;s bowel  18 .  
     [0086] The abdominal sac  112  may be similar to the abdominal sacs discussed above. For example, the abdominal sac is arranged for having a dialysate therein. This sac  112  is generally formed of a semi-permeable membrane having a porosity which precludes the dialysate within the abdominal sac  112  from escaping into the peritoneal region but still permits unconcentrated urine within the peritoneal region to enter the abdominal sac  112  through osmotic pressure. Because the abdominal sac  112  is required to function in an aqueous environment, it preferably is formed of a synthetic plastic material with some elastic qualities (e.g., Gortex-like cloth). However, the abdominal sac  112  should not be so elastic as to expand to an extent that permits the dialysate molecules or microstructures to exit from expanded pores of its walls.  
     [0087] As with the abdominal sacs discussed above, portions of the wall of the abdominal sacs  112  may alternatively be formed of an impermeable or substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom.  
     [0088] Still referring to FIG. 6, a section of the patient&#39;s bowel  18  is sutured to the abdominal sac  112 , thereby enclosing the extension  114  of the sac in the bowel. This extension includes the semi-permeable membrane wall so as to allow the unconcentrated urine drawn into the abdominal sac  112  by osmotic pressure to move into the bowel  18 , wherein the bowel functions to reabsorb water, electrolytes and small molecules, resulting in concentrated urine. However, the semi-permeable membrane wall prevents the dialysate from moving into the bowel, thus keeping the dialysate within the abdominal sac  112 .  
     [0089] The abdominal sac  112  preferably communicates with a subcutaneous access reservoir  51 , which includes an access section closely adjacent the patient&#39;s skin. The subcutaneous access reservoir (SAR)  51  permits the monitoring and testing of the dialysate and urine in order to determine the effectiveness of the prosthesis. The SAR  51  provides adjustment of urine flow and urine constituents by adding or subtracting dialysate to fit each patient&#39;s needs. The dialysate can be added or withdrawn from the SAR  51  using a syringe or tube inserted through the patient&#39;s skin into the reservoir.  
     [0090] Unlike the other embodiments of the invention discussed above, the prosthesis  110  does not include conduits for continuous mixing and circulation of unconcentrated urine and dialysate. In this regard, it should be noted that the prosthesis  110  is likely not as efficient as the other preferred embodiments because this prosthesis  110  does not take advantage of a respiratory pump. Accordingly, this prosthesis is better suited for patients having a less severe renal failure. Another possible disadvantage of this embodiment is that the abdominal sac  112  may be subject to layering and stagnation of dialysate and receive unconcentrated urine making the patient more susceptible to infection. In other words, the mixing and circulation provided by the prosthesis of the embodiments discussed above improves the efficiency of the dialysis and precludes layering and stagnation of fluids within the prosthesis. The possible layering and stagnation of the fluids may be minimized in this embodiment if the patient frequently moves or changes the angular orientation (e.g., vertical, horizontal) of their torso, to allow the fluids in the abdominal sac  112  to flow influenced by gravitational pull. However, one advantage of this prosthesis over the embodiments described above, is that this prosthesis  110  uses fewer elements and is more simple in its operation. This prosthesis  110  also creates less strain on the patient during surgery to implant the prosthesis than the prosthesis of other preferred embodiments since fewer elements are inserted into the body.  
     [0091] Referring to FIG. 7, there is shown at  120 , an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body in accordance with yet another preferred embodiment of this invention. The prosthesis  120  is similar to the prosthesis discussed above in FIGS.  1 - 6 , and particularly in FIGS.  1 - 4 . As shown in FIG. 7, the prosthesis  120  includes an abdominal sac  64  in the abdominal region of the patient below diaphragm  14 , a thoracic pouch  16  in the thoracic region of the patient&#39;s body above the diaphragm  14 , first and second conduits  26 ,  36  arranged for communicating fluid between the abdominal sac  64  and the thoracic pouch  16 , and a section of the patient&#39;s bowel  18  located within the abdominal section of the patient. The patient&#39;s urinary bladder  20  is connected to a downstream end of the bowel  18  preferably via the patient&#39;s distal right ureter  24  and the patient&#39;s cecum or appendix  22 .  
     [0092] The abdominal sac  64  is connected to the thoracic pouch  16  through the conduit  26 , which preferably includes a one-way valve  28  therein. The one-way valve  28  permits fluid to flow only in the direction of arrow  30  from the abdominal sac  64  into the thoracic pouch  16 .  
     [0093] The second conduit  36  is connected to the thoracic pouch  16  through a proximate end  122  and passes through the diaphragm  14  into and through the section of the patient&#39;s bowel  18 , which has been separated from the digestive system (or GI tract) of the patient. While not being limited to a particular theory, the second conduit  36  includes a one-way valve  38  near its proximal end  122  to permit fluid (e.g. dialysate and urine) to flow from the thorascic pouch  16  through the section of the patient&#39;s bowel  18  only in the direction of arrow  40 .  
     [0094] As can best be seen in FIG. 7, the second conduit  36  has a Y-shaped tubing that bifurcates into two conduit sections  124  and  126 . First conduit section  124  includes a distal opening  130 , and extends from the second conduit  36  into a first segment  128  of the bowel  18  until it ends at the distal opening  130 . The second conduit section  126  extends through a second segment  132  of the bowel  18  and has a distal end  134  connected to the abdominal sac  64  to recycle the flow of dialysate (and possibly some urine) back into the abdominal sac  64 , as will be described in greater detail below. While not being limited to a particular theory, the second conduit section  126  is provided with a one-way valve  48  at its distal end  134  to permit the fluid (e.g., dialysate and urine) to flow only in the direction of arrow  49  from the patient&#39;s bowel  18  to the abdominal sac  64 .  
     [0095] The first bowel segment  128  is sutured to the first conduit section  124  at the entrance  42  to the first bowel segment. The second bowel segment  132  is sutured to the second conduit section  126  at an entrance  136  to the second bowel segment and at an exit  44  from the bowel  18 .  
     [0096] The conduit sections  124 ,  126  have apertures  54  that are arranged to communicate within the bowel segments  128 , 132  so as to allow the unconcentrated urine and dialysate within the second conduit  36  to move into the bowel  18 . The bowel  18  functions to reabsorb water, electrolytes and small molecules, resulting in the formation of concentrated urine. As noted above, the section of bowel  18  is isolated from the rest of the bowel, and therefore from the Gastrointestinal (GI) tract. While not being limited to a particular theory, the section of bowel  18  that is selected preferably includes the right colon as the first bowel segment  128  and the ileum as the second bowel segment  132 . As noted above, the section of bowel  18  is capable of about 90% water reabsorption which translates to 10 to 20 liters of water per day.  
     [0097] Still referring to FIG. 7, a filter  138  is positioned at a lower end  140  of the section of bowel  18 . The filter  138  is a semi-permeable membrane that allows urine to pass through but blocks the dialysate from filtering through the membrane. While not being limited to a particular theory, the filter  138  is preferably disk-shaped and supported at its periphery by a plastic frame. The filter  138  is preferably held in place in the section of bowel  18  with an elastic member (e.g., rubber band) wrapped around the lower section  140  of the bowel  18  and the plastic frame. If desired, the plastic frame may include a groove or notch around its frame to assist in holding the filter  138  and elastic member in position within the bowel  18 .  
     [0098] The filter  138  functions similarly to the semi-permeable membrane  72  discussed above and shown in FIG. 3. As such, the semi-permeable membrane filter  138  is preferably a synthetic plastic material with some elastic quality having a porosity which precludes dialysate from filtering through the semi-permeable membrane, but permits urine to filter through the material. The filter  138  provides an alternate approach to the structure shown in FIG. 3 for filtering urine, but not dialysate, to the appendix  22 , which has a one-way peristalysis to the bladder  20 . As in the other embodiments, the bladder  20  appropriately excretes the concentrated urine based on the bladder&#39;s normal function.  
     [0099] Referring to FIG. 7, the urine remaining in the section of bowel  18  that is not filtered through the semi-permeable filter  138  is returned through the distal end  134  of the second conduit section  126  to the abdominal sac  64  for recirculation. While not being limited to a particular theory, the distal end  134  of the second conduit section  126  is preferably impermeable to preclude the escape of any urine therefrom.  
     [0100] The second conduit, its extension (the first conduit section  124 ), and the filter  138  form a fluid guide member  142  that is adapted to transfer unconcentrated urine from the thoracic pouch  16  via the second conduit into the separate section of bowel  18 , and to transfer dialysate from the thoracic pouch to the abdominal sac  64 .  
     [0101] As noted above, the prosthesis  120  shown in FIG. 7 is constructed similarly to the various prostheses discussed above. In this embodiment, the dialysate is not contained within a dialysis sac. While not being limited to a particular theory, the abdominal sac  64  preferably does not include or share a window with a dialysis sac, as shown, for example, in FIGS. 1 and 4. In FIG. 7, the abdominal sac  64 , thoracic pouch  16 , conduits  26 ,  36  and the section of bowel  18  provide a closed system for the dialysate, allowing the dialysate to cycle within the prosthesis  120 , but preventing the dialysate from leaving the prosthesis  120 .  
     [0102] As discussed above, the abdominal sac  64  is generally formed of a semi-permeable membrane having a porosity which precludes the dialysate within the abdominal sac  64  from escaping into the peritoneal region, but still permits unconcentrated urine within the peritoneal region to enter the abdominal sac  64  through osmotic pressure. Because the abdominal sac  64  is required to function in an aqueous environment, it preferably is formed of a synthetic plastic material with some elastic qualities (e.g., gortex-like cloth). However, the abdominal sac  64  should not be so elastic as to expand to an extent that permits the dialysate molecules or microstructures to exit from expanded pores of its walls.  
     [0103] As with the abdominal sacs discussed above, portions of the wall of the abdominal sac  64  may be formed of an impermeable or a substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom.  
     [0104] The unconcentrated urine and dialysate entering the abdominal sac  64  is directed through the first conduit  26  and the one-way valve  28  through the diaphragm  14  and into the thoracic pouch  16  by the internal body pumping mechanism described above. The unconcentrated urine and dialysate within the thoracic pouch  16  then pass through the Y-shaped second conduit  36  and the one-way valve  38  therein. The unconcentrated urine and dialysate are then directed through the two conduit sections  124 ,  126  to a respective one of the bowel segments  128 ,  132 . Movement of the urine and dialysate from the thoracic pouch  16  through the second conduit takes place by the internal body mechanism described above, which may be assisted or supplemented with a pump.  
     [0105] The conduit sections  124 ,  126  of the second conduit  36 , which direct the urine and dialysate into the section of the patient&#39;s bowel  18 , include a series of apertures  54  so as to allow the urine and dialysate within the conduit sections  128 ,  132  to flow out of the conduit  36 . The semi-permeable filter  138  that is within the bowel  18  has a porosity which precludes the dialysate that filtered through the holes  54  of the second conduit  36  from escaping from the bowel  18  into the appendix  22 , distal right ureter  24 , or bladder  20 , but still permits the urine, now concentrated, to permeate through the bowel  18 .  
     [0106] As noted above, when the unconcentrated urine is turned into concentrated urine within the separated section of the patient&#39;s bowel  18 , most of the concentrated urine will filter through the semi-permeable filter  138  and exit the bowel  18 . The concentrated urine will then flow into the urinary bladder  20  to be expelled intermediately, just as in a normally functioning human patient. The dialysate and returning urine is returned through the distal end  134  of the second conduit&#39;s second section  126  to the abdominal sac  64  for recirculation.  
     [0107] Referring to FIG. 8 there is shown at  150 , an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body in accordance with yet still another preferred embodiment of the invention, which is similar to the prostheses  10 ,  62 ,  70 ,  80  and  120  discussed above. As shown in FIG. 8, the prosthesis  150  includes an abdominal sac  64  in the abdominal region of the patient below diaphragm  14 , a thoracic pouch  16  in the thoracic region of the patient&#39;s body above the diaphragm  14 , a section of the patient&#39;s bowel  18  located within the abdominal section of the patient, and the patient&#39;s urinary bladder  20  connected to a downstream end of the bowel  18  through the patient&#39;s cecum or appendix  22  and a distal right ureter  24 . As described above in the other embodiments, the abdominal sac  64  is connected to the thoracic pouch  16  through a conduit  26 , including a one-way valve  28  therein. The one-way valve  28  permits fluid to flow only in the direction of arrow  30  from the abdominal sac  64  into the thoracic pouch  16 .  
     [0108] The prosthesis  150  includes a second conduit  36  having a proximal end  152  connected to the thoracic pouch  16 , and a distal end  154  connected to the abdominal sac  64 . While not being limited to a particular theory, the second conduit  36  passes through the diaphragm  14  and preferably includes a one-way valve  38  near its proximal end  152  to permit fluid (e.g., dialysate and unconcentrated urine) to flow from the thoracic pouch  16  into the peritoneal region only in the direction of arrow  40 .  
     [0109] The second conduit  36  of FIG. 8 includes a urine transfer sac  156  arranged to transfer unconcentrated urine to an extension of the second conduit, hereinafter referred to as a third conduit  158 . The third conduit  158  includes a urine receiving sac  160  arranged to receive unconcentrated urine from the urine transfer sac  156  and to transfer the urine to the separated section of bowel  18 . To transfer unconcentrated urine from the second conduit  36  to the bowel  18 , the third conduit  158  extends through and terminates in the section of bowel  18 . The second conduit  36 , its extension (the third conduit  158 ) and the semi-permeable membrane window  166  form a fluid guide member  182  that is adapted to transfer unconcentrated urine from the thoracic pouch  16  via the second and third conduits into the separated section of the patient&#39;s bowel  18 , and to transfer dialysate from the thoracic pouch  16  via the second conduit to the abdominal sac  64 .  
     [0110] The urine transfer sac  156  includes an impermeable outer wall  162 , and the urine receiving sac  160  includes an impermeable outer wall  164  coupled to the impermeable outer wall  162 . The urine transfer sac  156  and urine receiving sac  160  are separated by a semi-permeable membrane window  166  having pores or apertures that provide the window with a porosity which precludes dialysate within the urine transfer sac  156  from escaping into the urine receiving sac  160 , but permits urine within the urine transfer sac  156  to enter the urine receiving sac  160 . Therefore, in this example of the preferred embodiment, the dialysate is precluded from entry into the section of bowel  18 . Instead, the dialysate continues within a lower section  168  of the second conduit  36  toward the distal end  154 . The distal end  154  is provided with a one-way valve  48  to permit the fluid (e.g., dialysate and possibly some urine) to flow only in the direction of arrow  49  from the second conduit  36  into the abdominal sac  64 .  
     [0111] As can be seen in FIG. 8, the third conduit  158  includes a one-way valve  170  arranged to permit fluid, such as unconcentrated urine, to flow only in the direction of arrow  172  from the urine receiving sac  160  toward apertures  54  located downstream from the one-way valve  170 . As noted above, the third conduit  158  directs unconcentrated urine from the second conduit  36 , and in particular, the urine transfer sac  156 , to the section of bowel  18 , where the unconcentrated urine is turned into concentrated urine and eventually exits via the urinary bladder  20  intermittently, just as in a normally functioning human patient.  
     [0112] While not being limited to a particular theory, the third conduit  158  has a Y-shaped tubing that bifurcates into a first leg  174  and a second leg  176  downstream from the one-way valve  170 . The first leg  174  extends into and terminates within the first bowel segment  128 . The second leg  176  extends into and terminates within in the second bowel segment  132 . As can be seen in FIG. 8, the first bowel segment  128  is sutured to the first leg  174  of the third conduit  158  at the entrance  178  to the first bowel segment. The second bowel segment  132  is sutured to the second leg  176  at the entrance  180  to the second bowel segment. The first and second legs  174 ,  176 , which direct the unconcentrated urine into the section of the patient&#39;s bowel  18 , both include a series of apertures  54  large enough to allow the unconcentrated urine within the third conduit  158  to move out of the conduit and into the bowel  18  wherein the section of bowel functions to reabsorb water, electrolytes, and small molecules, resulting in the formation of concentrated urine.  
     [0113] As noted above, the section of the bowel  18  that preferably is selected includes the right colon and ileum, and is capable of 90 percent water reabsorption in the bowel, which translates to 10 to 20 liters of water per day. Also as noted above, the jejunum is anastomosed to the traverse colon to restore the integrity of the GI tract, and therefor, although the section of patient&#39;s bowel  18  is isolated from the GI tract, its blood supply remains intact so as to permit it to function in this invention.  
     [0114] As discussed above, the abdominal sac  64  is generally formed of a semi-permeable membrane having a porosity which precludes the dialysate within the abdominal sac  64  from escaping into the peritoneal region, but still permits unconcentrated urine within the peritoneal region to enter the abdominal sac  64  through osmotic pressure. The abdominal sac  64  is preferably formed of a synthetic plastic material with some elastic qualities. However, the abdominal sac should not be so elastic as to expand to an extent that permits the dialysate molecules or microstructures to exit from expanded pores of its walls.  
     [0115] As with the abdominal sac  64  discussed in other embodiments of this invention, portions of the wall of the abdominal sac  64  may alternatively be formed of an impermeable or a substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom.  
     [0116] Still referring to FIG. 8, the unconcentrated urine entering the abdominal sac  64  through the semi-permeable membrane, and the dialysate are directed through the first conduit  26  and the one-way valve  28 , through the diaphragm  14  and into the thoracic pouch  16  by the internal body pumping mechanism described above. The unconcentrated urine and dialysate within the thoracic pouch  16  then pass through the second conduit  36  and the one-way valve  38  therein to the urine transfer sac  156 . As noted above, the semi-permeable membrane window  166  precludes dialysate from filtering through the window, but allows the urine to pass through and into the urine receiving sac  160 . The dialysate is returned, possibly with some urine, through the lower section  168  of the second conduit  36  to the abdominal sac  64  for circulating and recycling. Preferably, the lower section  168  of the second conduit  36  is impermeable to preclude the escape of any urine and dialysate therefrom.  
     [0117] The unconcentrated urine that filters through the semi-permeable membrane window  166  passes through the one-way valve  170  into the bowel  18 , wherein the bowel  18  functions to reabsorb water, electrolytes and small molecules resulting in concentrated urine. The concentrated urine exits to the urinary bladder  20 , preferably via the distal right ureter  24  which can be attached to the cecum or appendix  22  when appropriate. The concentrated urine is expelled intermittently from the bladder, just as in a normally functioning human patient.  
     [0118] It should be noted that while the apertures  54  have been described in FIG. 1 as being relatively large (e.g., 0.5 cm), the size of the apertures should not be limited to relatively large holes for this embodiment, as the size of the holes only need to be large enough to allow unconcentrated urine to pass from the third conduit into the bowel  18 . The apertures  54  are shown in FIG. 8 by way of example, and should not limit the scope of the invention to apertures of any particular size, as long as the apertures allow urine to flow through.  
     [0119] While not being limited to a particular theory, it should be noted that the diameter of the lower section  168  of the second conduit  36  may be smaller than the diameter of the third conduit to augment the filtering of the unconcentrated urine through the semi-permeable membrane window  166  by creating an environment of higher pressure in the urine transfer sac  156  than in the urine receiving sac  160 . It is readily understood that such a pressure differentiation between the interiors of the sacs may increase the transfer rate of the unconcentrated urine through the semi-permeable membrane window  166 .  
     [0120] Furthermore, as noted above, the pumping action provided by the breathing cycle of the patient can be augmented, or even supplanted, by another device (e.g., a mechanical or electrical watertight pump) implanted in the person&#39;s body in fluid communication with the loop of circulating fluid. Such a pump could be positioned anywhere along the first or second conduits in any of the embodiments, as readily understood by a skilled artisan. If supplanting or augmenting the pumping action provided via the thoracic pouch, the mechanical or electrical pump would preferably be attached to the first or second conduit between the abdominal sac and the section of bowel  18 . The mechanical or electrical pump could be connected by wire to a subcutaneous power source (e.g., a battery) in a location where it could be periodically replaced if necessary or desired.  
     [0121] Referring to FIG. 9, there is shown at  184 , an exemplary fluid guide member  184  that is similar to the fluid guide member  182  shown in FIG. 8. Like the fluid guide member  182 , the fluid guide member  184  shown in FIG. 9 is adapted to transfer unconcentrated urine from a thoracic pouch via the second conduit  36  and third conduit  158  into the separated section of the patient&#39;s bowel  18 , and to transfer dialysate from the thoracic pouch via the second conduit  36  to an abdominal sac.  
     [0122] As best seen in FIG. 9, the fluid guide member  184  includes a safety outlet  186 . The outlet  186  is a pressure relief member arranged to communicate fluid from the second conduit  36  to the section of bowel  18  if the pressure in the prosthesis becomes greater than desired. While not being limited to a particular theory, the safety outlet  186  preferably includes a conduit  188  with a pressure sensitive one-way valve  190  therein. The conduit  188  preferably is attached to the urine transfer sac  156  and is sutured to the section of bowel  18  at an opening  194 .  
     [0123] It is understood that the conduit  188  could alternatively attach from another member of the prosthesis  150 , such as the abdominal sac  64 , first conduit  26 , thoracic pouch  16  or second conduit  36  to the section of bowel  18  for removing excess dialysate from the prosthesis to the bowel  18  and eventually out of the patient&#39;s body. It is noteworthy that such a pressure relief member communicates dialysate from a part of the prosthesis arranged to contain dialysate to a part of the prosthesis below or after a semi-permeable membrane member, such as the window  166 , that filters urine through while precluding dialysate from filtering through. As shown in FIG. 9, this communication is preferably between the urine transfer sac  156  and the section of bowel  18 .  
     [0124] Typically, the pressure in the prosthesis may become greater than desired if too much dialysate is present in the prosthesis. As discussed above, dialysate pulls unconcentrated urine into the prosthesis. If more dialysate is present in the prosthesis than desired, the dialysate may pull so much unconcentrated urine into the prosthesis that the abdominal sac  64  and thoracic pouch  16  become too full to operate efficiently as an internal body pump. Moreover, too much dialysate and unconcentrated urine in the prosthesis could possibly cause the sac  156  to expand beyond its elastic limit, or cause damage to the semi-permeable membrane window  166 . Accordingly, the fluid guide member  184  includes the safety outlet  186  to direct dialysate and unconcentrated urine from the urine transfer sac  156  to the section of bowel  18  when the pressure in the sac  156  becomes greater than desired.  
     [0125] The pressure sensitive one-way valve  190  permits fluid to flow only in the direction of arrow  192  from the urine transfer sac  156  to the section of bowel  18  when the pressure at the valve  190  becomes greater than a desired threshold. The desired threshold is preferably set above normal and allowable heightened pressure levels in the urine transfer sac  156 , and below a pressure level where damage to the sac  156  or semi-permeable membrane window  166  may occur. For example, a desired threshold may be two to three times the normal operating pressure in the prosthesis.  
     [0126] The safety outlet  186  relieves pressure on the urine transfer sac  156  and window  166  by directing dialysate and unconcentrated urine from the sac  156  directly to the section of bowel  18 . This transfer of fluids occurs when the pressure is high enough to open the pressure sensitive valve  190 . Under normal circumstances, when the amount of pressure on the urine transfer sac  156  and semi-permeable membrane window  166  is in a desired operating range, there is no need for the valve  192  to open. The pressure sensitive valve  192  only opens when the pressure is above a desired range, such as, when too much dialysate is in the prosthesis, to allow the safety outlet  186  to direct dialysate and unconcentrated urine to the section of bowel  18 , and thus, remove dialysate from the prosthesis. The removed dialysis escapes from the bowel  18  into the appendix  22  and eventually exits the patient via the urinary bladder  20  as discussed above.  
     [0127] Referring to FIG. 10 there is shown at  200 , an exemplary continuous internal peritoneal dialysis prosthesis inserted within a patient&#39;s body in accordance with another preferred embodiment of the invention, which is similar to the prostheses  10 ,  62 ,  70 ,  80 ,  120  and  150  discussed above. As shown in FIG. 10, the prosthesis  200  includes an abdominal sac  202  in the abdominal region of the patient below diaphragm  14 , a thoracic pouch  204  in the thoracic region of the patient&#39;s body above the diaphragm  14 , a section of the patient&#39;s bowel  18  located within the abdominal section of the patient, the patient&#39;s urinary bladder  20  connected to a downstream end of the bowel  18  through the patient&#39;s cecum or appendix  22  and a distal right ureter  24 .  
     [0128] The prosthesis  200  includes or is substantially similar to many features shown in the prosthesis  70  shown in FIG. 3, and in the prosthesis  150  shown in FIG. 8. For example, in addition to the features listed above, the prosthesis  200  includes a fourth conduit  206 , a semi-permeable membrane  72 , apertures  54  and one way valves  212 ,  220  substantially similar to the second conduit  36 , semi-permeable membrane  72 , apertures  54  and one way valves  38 ,  48  shown in FIG. 3. Further, the prosthesis  200  includes a second conduit  36 , a third conduit  158 , a urine transfer sac  156 , a urine receiving sac  160 , a semi-permeable membrane window  166 , one-way valves  38 ,  48 ,  170 , apertures  54 , a first segment  128  of the bowel  18  and a second segment  132  of the bowel substantially similar to the like numbered element shown in FIG. 8.  
     [0129] The abdominal sac  202  is substantially the same as previously described abdominal sac  64 . As can best be seen in FIG. 10, the abdominal sac  202  is connected to the thoracic pouch  204  through a conduit  26 , including a one-way valve  28  therein. The one-way valve  28  permits fluid to flow only in the direction of arrow  30  from the abdominal sac  202  into the thoracic pouch  16 . The abdominal sac  202  is also connected to the second conduit  36  and the fourth conduit  206  for receiving dialysate and some urine, as will be described below in greater detail.  
     [0130] The abdominal sac  202  is generally formed of a semi-permeable membrane having a porosity which precludes the dialysate within the abdominal sac  202  from escaping into the peritoneal region, but still permits unconcentrated urine (e.g., ultrafiltrate of blood) within the peritoneal region to enter the abdominal sac  202  through osmotic pressure. The abdominal sac  202  is preferably formed of a synthetic plastic material with some elastic qualities. However, the abdominal sac should not be so elastic as to expand to an extent that permits the dialysate molecules or microstructures to exit from expanded pores of its walls.  
     [0131] As with the abdominal sacs discussed in other embodiments of this invention, portions of the wall of the abdominal sac  202  may alternatively be formed of an impermeable or a substantially impermeable membrane that is more elastic than the semi-permeable membrane and does not permit the dialysate to exit, even when the impermeable or substantially impermeable membrane is expanded beyond its elastic limit. Therefore, before the semi-permeable membrane expands under pressure to an extent that could permit dialysate to exit, the impermeable or substantially impermeable membrane stretches to contain the dialysate while inhibiting the dialysate from exiting therefrom.  
     [0132] The prosthesis  200  includes a second conduit  36  having a proximal end  152  connected to the thoracic pouch  204 , and a distal end  154  connected to the abdominal sac  202 . While not being limited to a particular theory, the second conduit  36  passes through the diaphragm  14  and preferably includes a one-way valve  38  near its proximal end  152  to permit fluid (e.g., dialysate and unconcentrated urine) to flow from the thoracic pouch  204  into the peritoneal region only in the direction of arrow  40 .  
     [0133] The second conduit  36  of FIG. 10 includes a urine transfer sac  156  arranged to transfer unconcentrated urine to an extension of the second conduit, hereinafter referred to as a third conduit  158 . The third conduit  158  includes a urine receiving sac  160  arranged to receive unconcentrated urine from the urine transfer sac  156  and to transfer the urine to the separated section of bowel  18 . To transfer unconcentrated urine from the second conduit  36  to the bowel  18 , the third conduit  158  includes a distal opening  130 , and extends from the second conduit  36  into the first segment  128  of the bowel  18  until it ends at the distal opening. The first bowel segment  128  is sutured to the third conduit  158  at the entrance  178  to the first bowel segment.  
     [0134] As described above in reference to FIG. 8, the urine transfer sac  156  shown in FIG. 10 includes an impermeable outer wall  162 , and the urine receiving sac  160  includes an impermeable outer wall  164  coupled to the impermeable outer wall  162 . The urine transfer sac  156  and urine receiving sac  160  are separated by a semi-permeable membrane window  166  having pores or apertures that provide the window with a porosity which precludes dialysate within the urine transfer sac  156  from escaping into the urine receiving sac  160 , but permits urine within the urine transfer sac  156  to enter the urine receiving sac  160 . While not being limited to a particular theory, the dialysate is precluded from entry into the section of bowel  18 . Instead, the dialysate continues within a lower section  168  of the second conduit  36  toward the distal end  154 . The distal end  154  is provided with a one-way valve  48  to permit the fluid (e.g., dialysate and possibly some urine) to flow only in the direction of arrow  49  from the second conduit  36  into the abdominal sac  202 . Preferably, the lower section  168  of the second conduit  36  is impermeable to preclude the escape of any urine and dialysate therefrom.  
     [0135] As can be seen in FIG. 10, the third conduit  158  includes a one-way valve  170  arranged to permit fluid, such as unconcentrated urine, to flow only in the direction of arrow  172  from the urine receiving sac  160  toward apertures  54  located downstream from the one-way valve  170 . As noted above, the third conduit  158  directs unconcentrated urine from the second conduit  36 , and in particular, the urine transfer sac  156 , to the section of bowel  18 , where the unconcentrated urine is turned into concentrated urine and eventually exits via the urinary bladder  20  intermittently, just as in a normally functioning human patient.  
     [0136] The fourth conduit  206  has a proximal end  208  connected to the thoracic pouch  204 , and a distal end  210  connected to the abdominal sac  202 . Like the above discussed conduits  26 ,  36 , and  158 , the fourth conduit  206  is preferably made from silicon plastic, which is inert and does not cause peritoneal irritation. While not being limited to a particular theory, the fourth conduit  206  passes through the diaphragm  14  and preferably includes a one-way valve  212  near its proximal end  152  to permit fluid (e.g., dialysate and unconcentrated urine) to flow from the thoracic pouch  204  into the peritoneal region and bowel  18  only in the direction of arrow  214 . The thoracic pouch  204  is substantially similar to the thoracic pouch  16  described in the preferred embodiments above. Further to the thoracic pouch  16  described above, the thoracic pouch  204  includes an additional port connected to the fourth conduit  206  for permitting fluid to flow from the thoracic pouch  204  into the fourth conduit.  
     [0137] Still referring to FIG. 10, the patient&#39;s bowel  18  includes end sections sutured to the fourth conduit  206  at both an entrance  216  to the second segment  132  of bowel  18  and an exit  218  from the bowel  18 . The distal end  210  of the fourth conduit  206  extends through a lower end of the bowel  18  and is connected to the abdominal sac  202  to recycle the flow of dialysate and urine back into the abdominal sac. The distal end  210  is provided with a one-way valve  220  to permit the urine to flow only in the direction of arrow  222  from the patient&#39;s bowel  18  to the abdominal sac  202 .  
     [0138] The fourth conduit  206  is substantially similar to the second conduit  36  shown in FIG. 3. For example, the fourth conduit  206  includes a series of relatively large holes  54  that allow urine and dialysate to permeate from the conduit into the semi-permeable membrane  72 . The semi-permeable membrane  72  extends about the fourth conduit  206  within the bowel  18  and is attached to the fourth conduit at both an entrance  74  to the membrane  72  and the exit  76  from the membrane  72 . The semi-permeable membrane  72  is preferably a synthetic plastic material with some elastic qualities having a porosity which precludes dialysate from filtering through the semi-permeable membrane, but permits unconcentrated urine to filter through the material into the bowel  18 , wherein the bowel  18  functions to reabsorb water, electrolytes and small molecules resulting in concentrated urine.  
     [0139] A fluid guide member  228  includes the conduits and filters that are adapted to transfer unconcentrated urine form the thoracic pouch  204  into the separated section of bowel  18 , and to transfer dialysate from the thoracic pouch to the abdominal sac  202 . Referring to FIG. 10, the fluid guide member  228  includes the second, third, and fourth conduits  36 ,  158 ,  206 , the semi-permeable membrane window  166 , the semi-permeable membrane  72 , and the one-way valves located in the conduits.  
     [0140] As noted above, the section of the bowel  18  that preferably is selected includes the right colon or cecum and the ileum. The section of bowel  18  is capable of 90 percent water reabsorption, which translates to 10 to 20 liters of water per day. Referring to FIGS. 7, 8 and  10 , the first bowel segment  128  is preferably the right (ascending) colon and the second bowel segment  132  is preferably the ileum. Also as noted above, the jejunum is anastomosed to the traverse colon to restore the integrity of the GI tract, and therefor, although the section of patient&#39;s bowel  18  is isolated from the GI tract, its blood supply (e.g., arterial and venous) remains intact so as to permit it to function in this invention.  
     [0141] As also noted above, the pumping action provided by the breathing cycle of the patient can be augmented, or even supplanted, by another device (e.g., a mechanical or electrical watertight rate adjustable pump) implanted in the person&#39;s body in fluid communication with the loop of circulating fluid. Such an adjustable pump for circulating fluid within the prosthesis  200  is shown at  224  along the first conduit  26 . The mechanical or electrical pump  224  shown in FIG. 10 preferably includes a battery that provides power to the pump for moving fluid in the first conduit  26  from the abdominal sac  202  to the thoracic pouch  204  in the direction of the arrow  226 . As an alternative, the pump  224  could be connected by a wire to a subcutaneous power source (e.g., a battery) in a location where it could be periodically replaced if necessary or desired as understood by a skilled artisan.  
     [0142] In operation, the unconcentrated urine entering the abdominal sac  202  through the semi-permeable membrane and the dialysate are directed through the first conduit  26  and the one-way valve  28 , through the diaphragm  14  and into the thoracic pouch  204  by the internal body pumping mechanism, and if desired, by the pump  224  described above. Unconcentrated urine and dialysate within the thoracic pouch  204  pass through the second conduit  36  and the one-way valve  38  therein to the urine transfer sac  156 . As noted above, the semi-permeable window  166  precludes dialysate from filtering through the window, but allows the urine to pass through and into the urine receiving sac  160 . The dialysate is returned, possibly with some urine, through the lower section  168  of the second conduit  36  to the abdominal sac  202  for recirculating and recycling.  
     [0143] Unconcentrated urine and dialysate within the thoracic pouch  204  also pass through the fourth conduit  206  and the one-way valve  212  therein to the second segment  132  of the patient&#39;s bowel  18 . Movement of the unconcentrated urine and dialysate from the thoracic pouch  204  through the fourth conduit  206  takes place by the internal pumping mechanism described above, which may be assisted or supplemented with the pump  224 . The fourth conduit  206  includes a series of relatively large holes  54  so as to allow the unconcentrated urine and dialysate within the fourth conduit to flow out of the conduit within the semi-permeable membrane  72 . The semi-permeable membrane  72 , which is within the bowel  18  has a porosity which precludes the dialysate that filtered through the holes  54  of the second conduit  36  from escaping into the bowel  18 , but still permits the unconcentrated urine to permeate. The dialysate is returned, possibly with some urine, through the fourth conduit  206  to the abdominal sac  202  for recirculating and recycling.  
     [0144] The unconcentrated urine that filters through the semi-permeable membrane window  166  passes through the one-way valve  170  and apertures  54  into the bowel  18 . The unconcentrated urine that permeates through the semi-permeable membrane  72  passes into the bowel  18 . The bowel  18  functions to reabsorb water, electrolytes and small molecules resulting in concentrated urine. The concentrated urine exits to the urinary bladder  20 , preferably via the distal right ureter  24  which can be attached to the cecum or appendix  22  when appropriate. The concentrated urine is expelled intermittently from the bladder, just as in a normally functioning human patient.  
     [0145] It should be noted that the apertures  54  have been described in FIG. 1 as being relatively large (e.g., 0.5 cm). The size of the apertures  54  should not be limited to relatively large holes for this embodiment, as the size of the apertures only need to be large enough to allow unconcentrated urine to pass from the third and fourth conduits into the bowel  18 . The apertures  54  are shown in FIG. 10 by way of example, and should not limit the scope of the invention to apertures of any particular size, as long as the apertures allow urine to flow through.  
     [0146] While not being limited to a particular theory, it should be noted that the diameter of the lower section  168  of the second conduit  36  may be smaller than the diameter of the third conduit  158  to augment the filtering of the unconcentrated urine through the semi-permeable window  166  by creating an environment of higher pressure in the urine transfer sac  156  than in the urine receiving sac  160 . It is readily understood that such a pressure differentiation between the interiors of the sacs may increase the transfer rate of the unconcentrated urine through the semi-permeable window  166 .  
     [0147] As an alternative embodiment to the embodiment shown by example in FIG. 10, it is understood that the second conduit  36  and fourth conduit  206  could be merged at either or both of their proximal or distal ends, before the merged conduit attaches to one of the thoracic pouch  204  or the abdominal sac  202 . For example, instead of attaching both the second and fourth conduits to the thoracic pouch  204 , the fourth conduit  206  could be attached to the second conduit  36 , preferably below the one-way valve  38 . An advantage of this alternative embodiment is that the one-way valve  38  permits fluid to flow from the thoracic pouch  204  to both the second and fourth conduits, rendering the one-way valve  212  previously in the fourth conduit  206  unnecessary. This arrangement also provides the benefit that the thoracic pouch  204  does not attach directly to the fourth conduit  206  and thus does not require an attachment port for the fourth conduit. Further, the fourth conduit  206  does not pass through the diaphragm  14 . This arrangement of thoracic pouch  204  and conduits  36 ,  206  closely resembles the thoracic pouch  16  and second conduit  36  shown in FIG. 7, with the second conduit bifurcating into conduit sections  124  and  126 .  
     [0148] As another example of an alternative embodiment to the embodiment shown by example in FIG. 10, instead of attaching both the distal end  154  of the second conduit  36  and the distal end  210  of the fourth conduit  206  to the abdominal sac  202 , the distal end of the fourth conduit could be attached to the distal end of the second conduit, preferably before the one-way valve  48 . An advantage of this alternative embodiment is that the one-way valve  48  permits fluid to flow from both the second and fourth conduits to the abdominal sac  202 , rendering the one-way valve  220  previously in the fourth conduit unnecessary. This arrangement also provides the benefit that the abdominal sac  202  does not attach directly to the fourth conduit  206  and thus does not require an attachment port for the fourth conduit. In this arrangement, the abdominal sac  202  is substantially identical to the abdominal sac  64  described above.  
     [0149] The examples of the alternative embodiments to the embodiment shown in FIG. 10 attach the fourth conduit  206  to the second conduit  36 , instead of attaching the fourth conduit to either or both of the thoracic pouch  204  and abdominal sac  202 . While not being limited to a particular theory, it is understood that the alternative embodiments could likewise attach the second conduit  36  to the fourth conduit  206 , instead of attaching the second conduit to either or both of the thoracic pouch  204  and abdominal sac  202 .  
     [0150] It is understood that the size of the sacs, pouches, filters and conduits are preferably determined in accordance with several factors, such as the flow rate desired, the rate of clearance of wastes, and the size, metabolism, fluid intake, nutritional status, cardiac output, thickness of blood and concentration of blood of the patient. For example, an abdominal sac would be largerfor an adult (e.g., 500 cc-1000 cc) than for a child (e.g., 200 cc-500 cc). The amount of dialysate preferred in the prosthesis would likewise be affected by the size of the prosthesis and the desired output.  
     [0151] Yet another advantage of the prostheses described above is that they are generally made of an inert plastic regularly used inside the body for other purposes, as discussed above and readily understood by a skilled artisan. An entire prosthesis weighs less than about a pound, and preferably weighs less than about three ounces. Moreover, once implanted into a patient, the prosthesis is not visible and anatomical structures operate in their natural positions in the body.  
     [0152] It should be apparent from the aforementioned description and attached drawings that the concept of the present application may be readily applied to a variety of preferred embodiments, including those disclosed herein. For example, in FIG. 3. the distal end  46  of the second conduit  36  may include relatively large holes so as to allow unconcentrated urine and dialysis in the peritoneum to flow into the conduit  36  and the abdominal sac  64 . Likewise, In FIG. 2, the central section  66  of the second conduit  36  has a semi-permeable wall, and can also include relatively large holes  54 , as shown in the bowel  18  of FIG. 3. Similarly, in lieu of the relatively large holes  54  located in the second conduit  36  and the semi-permeable membrane  72  within the bowel  18  of FIG. 3, the conduit  36  within the bowel  18  can be constructed like the central region  66  of the conduit  36  shown in FIG. 2. That is, in FIG. 3, the conduit  36  within the bowel  18  can be formed of a semi-permeable membrane. Moreover, in FIG. 4, instead of coupling the distal end of the second conduit to the dialysis sac  84 , the distal end may extend to and end in the peritoneal space to return a percentage of the fluid to the peritoneum. In this example the distal end  46  of the conduit  36  should either be of a very small diameter, or employ a moderate pressure one-way valve  46  therein to control the flow of fluid into the peritoneal space in a manner that allows adequate residence time for the bowel to absorb water from the unconcentrated urine passing therethrough, but not such as to prevent flow of partially concentrated urine into the peritoneal space for lymphatic reabsorption and recycling through the entire system. Furthermore, in FIGS. 7 and 8, instead of having two sections or legs of a conduit communicate within the bowel, it is understood that the conduit could be constructed so that any number of sections or legs, including one, would extend into and communicate within the bowel. In addition, the ureter  24  could be connected directly to the bowel  18 , thus bypassing the appendix  22 . In this preferred embodiment, the appendix  22  would not be used.  
     [0153] It is within the scope of the invention that features of the exemplary embodiments discussed above can also be used in other of the exemplary embodiments. For example, as an alternative to the disk filter  138  shown in FIG. 7, the semi-permeable membrane  72  shown in FIG. 3 could be used to extend about the conduits in the section of bowel  18 . Moreover, portions of the first leg  174  and second leg  176  of the third conduit  158  that extend into the bowel  18  could alternatively be formed of a semi-permeable membrane, as shown for the second conduit  36  in FIG. 2. In addition, while not preferred, the first conduit  26  of any of the embodiments could include apertures  54 , as shown in FIG. 3. Also, the conduits shown in FIG. 10 could be augmented or replaced by other conduits as shown by example in FIGS.  1 - 9 . For example, the fourth conduit  206  could be supplanted by a conduit having the structure exemplified by the second conduit  36  of FIG. 2.  
     [0154] Without further elaboration the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, readily adapt the same for use under various conditions of service.