Patent Publication Number: US-6911014-B2

Title: Continuous flow peritoneal dialysis catheter

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of application Ser. No. 10/057,340, filed Jan. 23, 2002, now U.S. Pat. No. 6,749,580, issued on Jun. 15, 2004, entitled “Catheter”, which claims priority from U.S Provisional Application Ser. No. 60/327,515, filed on Oct. 5, 2001, entitled “Continuous Flow Peritoneal Dialysis”, of which Claudio Ronco and Angela Gloukhoff are inventors. 

   BACKGROUND OF THE INVENTION 
   Continuous flow peritoneal dialysis is a technique which utilizes a certain amount of fluid, generally dialysate, which is constantly present in the abdomen. Continuous flow peritoneal dialysis previously know in the art has utilized two single lumen peritoneal dialysis catheters or a modified large bore hemodialysis catheter. The inflow and uptake catheters enable the inflow and outflow to remain constant. However, high dialysate flow rates and re-circulation due to channeling or poor mixing inside the peritoneal cavity are problems associated with continuous flow peritoneal dialysis. 
   In the continuous flow peritoneal dialysis technique, the peritoneal dialysis solution is either utilized in a single pass or a re-circulation loop. Various re-circulation systems, such as sorbent cartridges or dialyzers, are known. A problem has been the quick drainage of fresh solution before coming into contact with the peritoneal exchange surface. 
   Regeneration systems include utilizing a batch of moderate volume prepared fluid and re-circulating the fluid until it saturates. Another method provides an initial fixed volume of commercial dialysis solution for priming, followed by continuous regeneration of the spent dialysate. Regeneration can be performed either by a hemodialysis filter or by absorption. Another method is preparation of solutions from water in concentrate with on-line ultra-filtration. 
   The proximal ends of the two lumens are attached to a dialysate regeneration means. Regenerated dialysate, or fresh dialysate, are introduced into the abdomen through one of the catheters, which is connected to a means for providing regenerated or fresh dialysate, which is well known in the art. 
   For all of the aforementioned reasons, it is important to have a continuous flow peritoneal dialysis catheter and method which effectively allow the dialysate to mix into the peritoneum while reducing trauma to the peritoneal walls. In addition, it is important to have catheters, and diffusers for catheters, that gently dispense the matter flowing through the catheter. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention relates generally to continuous flow catheters with at least two lumens, one of which is a short lumen, and the other of which is a long lumen. In this invention, the long lumen, which is the uptake lumen, is coiled. It may have a plurality of openings, generally located on the inside of the coil, for the intake of matter flowing through the catheter. 
   The catheter also may include a diffuser, which is located over the distal end of the short lumen, for dispensing matter into the body of the user. The long lumen may extend beyond, and/or through, the diffuser. 
   The catheter may also include a hub at the proximal ends of the at least two lumens. The hub may be passable subcutaneously through the body of the user of the catheter, or the hub may be detachable. 
   The catheter of the current invention may be used for peritoneal dialysis. 
   In addition, the catheter may include at least one cuff located proximally to the peritoneal membrane for the adherence of subcutaneous tissue. The catheter may contain lumens which are “D” shaped. 
   The current invention also relates to diffusers for a catheter, as well as catheters having a diffuser. The diffuser has an interior portion and an exterior portion and at least one opening for the dispensing of matter into the body of the user. In addition, the diffuser may have a plurality of openings through which the matter may be dispensed into the body of the user in a diffused manner. The plurality of openings may be located radially around the sides of the diffuser in a generally perpendicular manner to the longitudinal axis of the catheter. The shapes of the diffuser generally consist of cylindrical, teardrop, bell, round, oval, semi-round, semi-oval and a combination of shapes. The diffuser, and catheter having a diffuser, may be used on a catheter used for a continuous flow peritoneal dialysis. 
   The current invention also includes methods for a continuous flow peritoneal dialysis which include the steps of creating an incision in the body of the user and separating the anatomical layers, making a circular suture in the peritoneal membrane, making an incision in the peritoneal membrane, inserting the catheter, and tightening the parietal peritoneum. The method also may include anesthetizing the skin and peritoneal surface. In addition, the method may include making a lateral incision in the skin of the user, creating a skin tunnel, passing the catheter through the skin tunnel, connecting attachments to the catheter, and suturing the skin incision. The method may also include providing a catheter having a diffuser. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention, and together with the description, serve to explain the principles of the invention. In the drawings, the same reference numerals are employed for designating the same elements throughout the several figures. 
       FIG. 1A  is a perspective view of the cylindrically shaped diffuser; 
       FIG. 1B  is a side elevation view of a round and/or oval diffuser; 
       FIG. 1C-1  is a perspective view of a semi-oval shaped diffuser having a “D” shaped long lumen; 
       FIG. 1C-2  is a perspective view of a semi-round shaped diffuser having a round shaped long lumen; 
       FIG. 1D  is a perspective view of a teardrop shaped diffuser; 
       FIG. 1E  is a side elevation view of a bell shaped diffuser; 
       FIG. 2A  is a top elevation view of a catheter with a diffuser and with no hub; 
       FIG. 2B  is a top elevation view of a catheter with a diffuser and a hub; 
       FIG. 2C  is a top elevation view of a catheter with a diffuser and a detachable hub; 
       FIG. 2D  is a top elevation view of a catheter with a diffuser and with an optional hub of any kind; 
       FIG. 3  is a top elevation view of a catheter without a diffuser and with an optional hub of any kind; 
       FIG. 4  is a cross section of a diffuser; 
       FIG. 5A  shows the catheter in utility; 
       FIG. 5B  is a view of the diffuser in utility; 
       FIG. 5C  is a view of a tunneled proximal end; 
       FIG. 5D  is a view of a tunneled proximal end; 
       FIG. 6A  is a cross section of a hub; 
       FIG. 6B  is a cross section of the double “D” lumens in the hub; 
       FIG. 6C  is a cross section of the extenders in the hub; 
       FIG. 7  is a flow chart of a method for continuous flow peritoneal dialysis; 
       FIG. 8A  is a side view of the long lumen extended; 
       FIG. 8B  is a cross section showing two double “D” shaped lumens; 
       FIG. 8C  is a cross section showing two round shaped lumens; 
       FIG. 9  is an exploded side view of an alternate embodiment of a catheter according to the present invention. 
       FIG. 10  is a side elevational view of the catheter of  FIG. 9 , showing a connector disposed within a diffuser. 
       FIG. 10A  is a sectional view of a proximal portion of the catheter taken along lines  10 A— 10 A of FIG.  10 . 
       FIG. 10B  is a sectional view of a proximal portion of the catheter taken along lines  10 B— 10 B of FIG.  10 . 
       FIG. 11A  is a perspective view of a connector according to the present invention. 
       FIG. 11B  is a side elevational view of the connector of FIG.  11 A. 
       FIG. 11C  is a front elevational view of the connector of FIG.  11 A. 
       FIG. 11D  is a sectional view of the connector taken along lines  11 D— 11 D of FIG.  11 C. 
       FIG. 12A  is a perspective view of a diffuser according to the present invention. 
       FIG. 12B  is a side elevational view of the diffuser of FIG.  12 A. 
       FIG. 12C  is a sectional view taken along lines  12 C— 12 C of FIG.  12 B. 
       FIG. 12D  is a front elevational view of the diffuser of FIG.  12 A. 
       FIG. 13  is an enlarged sectional view of the connector and diffuser of  FIGS. 11A-12D , connected to catheter lumens according to the embodiment of FIGS.  9  and  10 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In describing embodiments of the invention illustrated in the drawings, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. The words “proximal”, “distal,” “short” and “long” are used herein for exemplary purposes, and are not to be taken as a limitation on the present invention. The words “proximal” and “distal” refer to directions away from and closer to, respectively, the insertion tips of the first and second lumens according to the present invention. The words “short” and “long” designate the length of lumens relative to one another. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import. The following describes preferred embodiments of the invention. However, it should be understood based on this disclosure, that the invention is not limited by the preferred embodiments described herein. 
   Reference is now made to  FIGS. 2A ,  2 B,  2 C,  2 D, and  3  which show the catheter  10 ,  10 ′ of the current invention. As seen in these figures, the catheter contains at least two lumens, a first lumen  12  and a second lumen  14 . The second lumen  14  is longer than the first lumen  12 . For explanatory purposes, the second lumen  14  also is referred to as a long lumen  14  and the first lumen  12  also is referred to as a short lumen  12 . Each lumen has a proximal end  16 ,  18  and a distal end region,  20 ,  22 . Each of the distal end regions,  20 ,  22  of each of the at least two lumens  12 ,  14  has at least one opening  24 ,  26  for the passage of matter  42  into or out of the body of the user of the catheter  10 ,  10 ′. Matter  42  passes through the longitudinal lumen channel  112  defined by the lumen wall  90 . 
   The catheter  10 ,  10 ′ of the present invention can be adapted for use in various applications in which bodily fluids, medicaments or other solutions are introduced into and removed from the body such as perfusion, infusion, plasmapheresis, hemodialysis, chemotherapy, and the like. The area to be catherized may be the peritoneum, and may be any suitable area within the body. Other areas in which the catheter  10 ,  10 ′ may be used include, for example, any abscess cavity, post-operative cavity, and other areas of the body including inter-abdominal, sub-diaphragmatic and sub-hepatic areas. It should be understood by one of ordinary skill in the art from this disclosure that these areas are exemplary, and that the catheter  10 ,  10 ′ may be used to remove or introduce matter in various areas to be catherized. In addition, it will be understood by one skilled in the art based on this disclosure, that the catheter  10 ,  10 ′ can be configured and adapted by increasing or decreasing the catheter size and/or number of catheters and/or lumens such that the catheter  10 ,  10 ′ can be beneficially used for other medical applications in which matter is introduced into and/or removed from the body. 
   Matter  42  may pass into the body of the user of the catheter through the short lumen  12 , which also can be referred to as the delivery lumen. Matter may be removed from the body of the user of the catheter  10  through the long lumen  14 , which also can be referred to as the uptake or return lumen. However, it is to be understood that within the scope of the invention the long lumen  14  also may be a delivery lumen and the short lumen  12  may be an uptake lumen. 
   The long lumen  14  can be coiled and has at least one opening  26  for the passage of matter through the lumen. The at least one opening  26  can be at the distal end  96  of the lumen  14 . In addition, it is within the scope of this invention to place the at least one distal opening  26  along the side  98  of the distal end region  22  of the long lumen  14 . 
   The long lumen  14  may have a plurality of openings  26  along the side  98  of the distal end region  22  of the lumen. 
   The plurality of openings  26  also may be located along the side  98  of the distal end region  22  of the lumen in a manner whereby all of the plurality of openings  26  are located on the inside of the coiled distal end region  22  of the lumen.  FIG. 8A , which extends the coil for exemplary purposes, illustrates this embodiment. In addition, a distal opening  26 , optionally may be included at the end  96  of the distal end region  22  of the lumen  14 . 
   As seen in  FIG. 8B , the lumens  12 ,  14  each may have a “D” shape. However, it is within the scope of the invention to have lumens  12 ,  14  that are round in shape, as seen in FIG.  8 C. The lumen  12 ,  14  shapes as shown in  FIGS. 8B and 8C  are intended to be exemplary only of the variety of lumen shapes that can be used with the present invention. It will be understood, based on this disclosure, that the present invention is not limited to the configurations shown in  FIGS. 8B and 8C . One skilled in the art will appreciate that all shapes of the lumens known in the art and to be discovered are within the scope of the invention. In addition, the lumens each may have shapes and sizes that vary from the other lumen or lumens. 
   Optionally, as know in the art, a radiopaque strip  94  may be included in the lumen wall  90  of either the short lumen  12  or the long lumen  14  to distinguish the lumens from one another, particularly at their proximal ends  16   18 . Generally, the radiopaque strip  94  will be placed in the long lumen  14  as the longer length enables the user to more readily identify the radiopaque strip  94 . 
   Reference is now made to  FIGS. 1A through 1E ,  2 A through  2 D,  4 ,  5 A and  5 B, which illustrate a diffuser  30 . It is to be noted that the embodiment of the catheter  10 ′ that is illustrated in  FIG. 3  does not contain a diffuser. The diffuser  30  may be added to the catheter  10  and located over the at least one distal opening  24  in the short lumen  12 . The long lumen  14  extends beyond the diffuser  30  more distally into the body of the user of the catheter. As seen most clearly in  FIGS. 1C-1 ,  1 C- 2 , and  4 , the long lumen  14  may extend through the diffuser  30 . In  FIG. 1C-1 , the long lumen  14  is “D” shaped. In  FIG. 1C-2 , the long lumen  14  has a round shape. 
   The diffuser  30  has an interior portion  32  and an exterior portion  34  and at least one opening  36  between the interior portion  32  and the exterior portion  34 . The matter  42  being dispensed in the body of the user flows through the short lumen  12  and into the diffuser  30  at the distal end opening  24  of the lumen  12 . Thereafter, the matter  42  flows through the at least one opening  36  of the diffuser and into the body of the user. 
   The diffuser  30  may have a plurality of openings  36  through which the matter  42  enters the body of the user in a diffused manner. In addition, the plurality of openings  36  may be located radially around the sides of the diffuser  30  in a generally perpendicular manner to the longitudinal axis of the catheter  10 . 
   The catheter  10  of the current invention may be used for continuous flow peritoneal dialysis. In peritoneal dialysis, the matter  42  flowing through the catheter may be dialysate. The diffuser  30  of the current invention enables a gentle interaction on the peritoneal structures from the effects of high dialysate flow rates, and enables the dialysate solution to readily mix into the peritoneal cavity  40 . When used for continuous flow peritoneal dialysis, the radially located openings  36  allow dialysate  42  to exit perpendicularly generally  360  degrees from the diffuser. 
     FIGS. 1A through 1E  illustrate various shapes in which a diffuser  30  may be formed.  FIG. 1A  illustrates a cylindrical shape,  FIG. 1B  illustrates an oval and/or round shape,  FIG. 1C-1  illustrates a semi-oval shape,  FIG. 1C-2  illustrates a semi-round shape,  FIG. 1D  illustrates a teardrop shape and  FIG. 1E  illustrates a bell shape. In addition, a diffuser  30  may be made of combinations of the shapes illustrated in  FIGS. 1A-1E . The diffuser  30  configurations as shown in  FIGS. 1A through 1E  are intended to be exemplary only of the variety of configurations achievable with the present invention. It will be understood, based on this disclosure, that the present invention is not limited to the configurations shown in  FIGS. 1A through 1E . 
   When used for continuous flow peritoneal dialysis, the diffuser  30  provides even disbursement of the dialysate  42 . The plurality of openings  36  diffuses the delivery pressure of the dialysate  42 , which can provide a gentle interaction on the peritoneal membrane  38 . 
   It is to be understood that the dimensions of the invention may be varied for different size catheters, embodiments, and different characteristics unique to the user of the catheter. Examples of dimensions that may be used include the following: the proximal end of the diffuser  30  may be located less than 1 mm from the peritoneal membrane  38 . Also, the distance between the distal end of the diffuser  30  and the beginning of the spiral at the distal end region  22  of the long lumen  14  may be approximately 15 cm in length. While the length of the spiral distal end region  22  of the long lumen  14  may vary, its length may be approximately 8.875 inches. Lumen resistance may yield in the range of 100 to 300 ml/min. When the diffuser  30  is cylindrical in shape, the width  28  of the cylinder  1 A 1  may be 0.5 cm long. While any number of openings  36  can be used, diffusers  30  may have openings in numbers ranging from six to twenty-four. It is to be understood that these dimensions are exemplary only, and are not to be taken as limitations on the invention. 
   As clearly illustrated in  FIG. 4 , the interior portion  32  of the diffuser  30  may have a proximal bonding region  82  and a distal bonding region  84 , which are regions onto which the lumen wall  90  of the long lumen  14  may be bonded to the diffuser  30 . The bonding may be accomplished by means of glue, adhesive, heat bonding, or other means currently known in the art or to be discovered. 
   Reference is now made to  FIG. 5A , which shows the general location of the catheter  10  in the peritoneum  100 , when the catheter  10  is used for continuous flow peritoneal dialysis. The diffuser  30  is located just distally to the peritoneal membrane  38 . The coiled distal end region  22  of the long lumen  14  is located in the lower Douglas cavity  92  of the peritoneum  100 . In use, the catheter  10  separates the delivery and return of the dialysate  42 . As a result, there is minimal recirculation of the spent dialysate  42 . In use, the fresh dialysate  42  enters the peritoneum  100  through the diffuser  30 . The dialysate  42  passes through the peritoneum  100  where the necessary physiological and chemical processes occur, and which turn the fresh dialysate into spent dialysate. Constant intra-peritoneal volume can be maintained with high dialysate into spent dialysate. Constant intra-peritoneal volume can be maintained with high dialysate flow rates to maintain a high solute concentration gradient between plasma and continuously renewed dialysate solution  42 . The spent dialysate  42  is aspirated back out of the peritoneum  100  through the at least one opening  26  of the long lumen  14 . 
   The coiled design of the distal end region  22  of the long lumen  14  increases the bulk tubing which separates the parietal and visceral layers of the peritoneum  100  from obstructing the at least one distal opening  26  for outflow of the spent dialysate  42 . The use of a plurality of openings  267  can increase the outflow rate. The use of a coiled long lumen  14  distal end region  22  is preferred for peritoneal dialysis because it is more gentle to the viscera than the tip of a straight lumen. 
   Preferably, the catheter  10 ,  10 ′ is made of a low durometer silicone. However polyurethane or other biocompatible materials known in the art or to be developed may also be used. Low durometer silicone is preferable because of its biocompatibility and softness, which is beneficial for use in the peritoneum  100 , which is a relatively soft body structure. In addition, low durometer silicone is flexible in a large range of temperatures and has not clinically harmful leachable plasticizers. 
   The first lumen  12 , the second lumen  14 , and additional lumens in catheters having more than two lumens, and the diffuser  30  may be made of a biocompatible plastic or elastomer, more preferable from a biocompatible elastomer. Suitable biocompatible plastics include materials such as, for example, polyethylene, homopolymers and copolymers of vinyl acetate such as ethylene vinyl acetate copolymer, polyvinylchlorides, homopolymers and copolymers of acrylates such as polymethylmethacrylate, polyethylmethacrylate, polymethacrylate, ethylene glycol dimethacrylate, ethylene dimethacrylate and hydroxymethyl methacrylate, polyurethanes, ployvinylpyrrolidone, 2-pyrrolidone, polyacrylonitrile butadiene, polycarbonates, polyamides, fluoropolymers such as homopolymers and copolymers of polytetrafluoroethylene and polyvinyl fluoride, polystyrenes, homopolymers and copolymers of styrene acrylonitrile, cellulose acetate, homopolymers and copolymers of acrylonitrile butadiene styrene, polymethylpentene, polysulfones, polyesters, polyimides, polyisobutylene, polymethylstyrene and other similar compounds known to those skilled in the art. It should be understood that these possible biocompatible polymers are included above for exemplary purposes and should not be construed as limiting. If a biocompatible polymeric material is used to form the catheter  10 ,  10 ′ it is most preferred that the polymeric material include a polyurethane or a polyolefin polymeric material having a preferably soft durometer, as specified below. 
   Suitable, preferred, biocompatible elastomers for use in forming the catheters  10 ,  10 ′ include biocompatible elastomers such as medical grade silicone rubbers polyvinyl chloride elastomers, polyolefin homopolymeric and copolymeric elastomers, urethane-based elastomers, and natural rubber or other synthetic rubbers. The catheter  10 ,  10 ′ may be made of the elastomeric material such that they are flexible, durable, soft, and easily conformable to the shape of the area to be catheterized and/or the subcutaneous area and minimize risk of harm to vessel walls. If the catheter  10 ,  10 ′ is used for hemodialysis applications, they may be formed of a soft silicone elastomer which has a hardness of at least about 80-A on a Shore durometer scale. Such an elastomer is available from Dow Coming, and can include 20% barium sulfate in the elastomer to provide radiopacity. While it is preferred to have a higher Shore durometer hardness if a biocompatible elastomer is used, particularly for hemodialysis, it is also possible to make a device from an elastomer having a lower Shore durometer hardness without departing from the spirit of the invention. It will be understood, based on this disclosure, that the catheter  10 ,  10 ′ may also be radiopaque depending on its intended use. 
   Reference is now made to  FIGS. 2B ,  2 C,  2 D,  3 ,  5 C,  5 D and  6 A through  6 C, which show the invention with a hub  50 , which is optional. When a hub  50  is provided, the proximal ends  16 ,  18  of the at least two lumens  12 ,  14  are located in the hub  50 . The lumens  12 ,  14  may be attached to the hub  50  in a nonremovable manner, as seen in FIG.  2 B. Alternatively, the lumens  12 ,  14  may be attached to a detachable hub  50 ′, as seen in FIG.  2 C. Detachable hubs are disclosed in a pending application, U.S. Provisional Application Ser. No. 60/329,593, entitled “Detachable Hub,” which is incorporated herein by reference. In addition, as illustrated in  FIGS. 2D and 3 , the use of all hubs  110  currently known in the art or to be discovered is within the scope of the invention. However, as illustrated in  FIG. 2A , the hub is optional, and the hubs included for exemplary purposes should not be construed as limiting. One skilled in the art will appreciate that the catheter  10 ,  10 ′ of the current invention may be used with a hub  50 , a detachable hub  50 ′, with no hub, or with hubs  110 , or other attachments  110 , currently known in the art or to be discovered. 
   In an embodiment of the invention, as seen in  FIGS. 2B ,  5 C,  5 D and  6 A- 6 C, a non-removable hub  50  may be utilized. As seen in these figures, the proximal ends  16 ,  18  of the at least two lumens  12 ,  14 , end in the hub  50 . In addition, the distal ends of extenders  56 ,  58  also end in the hub  50 . In this embodiment, when the lumens  12 ,  14  are “D” shaped, the proximal end openings  102 ,  104  of the lumens  12 ,  14  each are “D” shaped. Further, as seen in the embodiment illustrated in  FIGS. 6A through 6C , the distal openings  106 ,  108  of the extenders  56 ,  58  each may have a round shape. The extension distal end openings  106 ,  108  and the proximal end openings,  102 ,  104  of the at least two lumens  12 ,  14  are brought into fluid communication with each other via hub channels  52 ,  54  molded in the hub  50 . The hub  50  is molded around a removable interior pin (not shown) that is round at one end and “D” shaped at the other end. The shapes, sizes, and number of the lumens and extenders utilized with the hub  50  are exemplary, and not intended to be limiting. The extension proximal ends (not shown) are preferably connected to respective female luer locks (not shown) in a conventional manner. If decided, the female luer locks may be substituted with any suitable type of quick connect fittings, ferrule connectors, threadable connectors, or any connection means known in the art or to be discovered to achieve the flow of matter through the catheter  10 ,  10 ′. The extenders, as known in the art, may be connected in fluid communication to respective fluid inlets and outlets of the dialysis unit, other fluid transfer equipment, or other apparatus needed to carry out the purpose for the catheter  10 ,  10 ′. 
   As previously mentioned, the hub  50 ,  50 ′ and extenders  56 ,  58  of the catheter  10 ,  10 ′ are optional. The proximal end of the catheter  10 ,  10 ′ of the present invention can be formed simply as at least two lumens  12 ,  14 . The proximal ends  16 ,  18  of the lumens could be made connectable to dialysis equipment or other apparatus by providing luers or other connectors to the proximal ends  16 ,  18  of the lumens with a hub or additional extenders. 
   When the catheter  10 ,  10 ′ has a hub  50  that is not detachable, generally, the hub  50  will be passable through the subcutaneous layer  48  of the body of the user of the catheter. As seen in  FIGS. 5C and 5D , the lumen proximal ends  16 ,  18 , the hub  50  and the extenders  56 ,  58  may be passed through a subcutaneous tunnel in the subcutaneous layer  48  of the body using various tunneling techniques. The lumen proximal ends  16 ,  18  the hub  50  and the extenders  56 ,  58  may be inserted in a tunnel entrance incision  86  and tunneled through the subcutaneous layer  48  to the tunnel exit incision  86 . Alternatively, the lumen proximal ends  16 ,  18  the hub  50  and the extenders  56 ,  58  may be inserted in the catheter entrance incision  110  and tunneled through the subcutaneous layer  48  to a tunnel exit incision  86 . In like matters, in catheters  10 ,  10 ′ that do not have hubs or that have detachable hubs  50 ′, the lumen proximal ends  16 ,  18  may be subcutaneously tunneled. 
   Reference is now made to  FIGS. 2A through 2D ,  3 ,  4 , and  5 A- 5 D, which illustrate the inclusion of at least one cuff  44 , which is optional. In addition, a second cuff  46  may also be included, which is optional. The at least one cuff  44 , as known in the art is made of a material, generally polyester, onto which the tissue of the user of the catheter may grow in order to secure the catheter  10 ,  10 ′ to the body of the user. A cuff  44  is located just proximally to the peritoneal membrane  38 , when the catheter  10 ,  10 ′ is used for continuous flow peritoneal dialysis. The cuff  44  may be located between 0 and 5 mm proximally from the peritoneal membrane  38 . If the peritoneal membrane  38  is sutured at the incision site of the catheter  10 ,  10 ′, added space may be needed because the suture, when pulled, may create folds in the membrane  38 . Preferably, the space between the diffuser  30  and the cuff  44  will be in the range of between 0.5 and 10 mm. The range of distance between the first cuff  44  and the second cuff  46  preferably will be 10 cm. It is to be understood that the dimensions relating to the cuffs  44 ,  46  may be varied for different size catheters, embodiments, and different characteristics unique to the user of the catheter. The dimensions listed are not intended to be limiting, rather they are included for exemplary purposes. 
   As seen in  FIGS. 5C and 5D , a second cuff  46  may be located under the skin distally to the exit hole  86  for the catheter  10 ,  10 ′. 
   Reference is now made to  FIG. 7 , which is a flowchart for the method for continuous flow peritoneal dialysis of the current invention. The method includes creating an incision in the body of the user and separating anatomical layers until the peritoneum is found  62 ; making a circular suture in the peritoneal membrane  64 ; inserting the distal end of the catheter into the Douglas cavity of the peritoneum, guided by a semi-rigid wire inside the outflow lumen, and tightening the parietal peritoneum between the diffuser and cuff by tightening the circular suture in the peritoneal membrane  68 . In addition, the method may include anesthetizing under the skin down to the peritoneal surface with a syringe  60 . Also, the method may include making a lateral incision in the skin of the user  70 ; creating a subcutaneous tunnel, also known as a skin tunnel  72 ; passing the proximal end of the catheter subcutaneously through the skin tunnel  74 , which may be accomplished by means of a tunneler; attaching connecting attachments to the lumens  76 ; and suturing the incision in the skin  78 . 
   The method may also include providing a catheter  10  that has a diffuser  30 . 
   The incision of step  62  may be about 3 cm long, and the incision of step  70  may be about 10 cm long. It is to be understood that the dimensions of the incisions may be varied for different size catheters, embodiments, and different characteristics unique to the user of the catheter. The dimensions listed are not intended to be limiting, rather they are included for exemplary purposes. 
   A sheath (not shown), as commonly known in the art, may be inserted over the diffuser before insertion of the catheter  10  into the body. Because the diffuser  30  preferably is made of a low durometer silicone, it may be easily compressed into the optional sheath. The sheath diminishes the volume of the diffuser  30 , which may enable the insertion of the catheter  10 , including the diffuser  30 , utilizing a smaller incision than would be possible without use o a sheath. A Quill sheath is commonly known in the art, and may be used for a catheter  10  that does not have a hub. If the catheter  10  has a hub  50 , which is not removable, a tear-away sheath, which is commonly known in the art, may be used. 
   When a catheter  10 ,  10 ′ having a hub  50  which is not detachable is passed through the skin tunnel subcutaneously  76 , the subcutaneous layer  48  will have to stretch to enable the hub  50  to pass. Normally, the elasticity of the subcutaneous layer  48  will enable the subcutaneous tissue to encapsulate the lumens  12 ,  14  after passage of the hub  50 . When a detachable hub  50 ′ is utilized on the catheter  10 ,  10 ′, the hub  50 ′ is among the attachments connected to the catheter during the step  76  of connecting attachments to the catheter. 
   As known in the art, the open ends of the luer locks may be connected in fluid communication to respective fluid inlets and outlets of the dialysis unit, or other fluid transfer equipment in order to begin dialysis. 
   An alternate embodiment of a catheter  200  according to the present invention is shown in  FIGS. 9-12D . The catheter  200  includes a proximal portion  202  and a distal portion  204 , connected by a connector  206 . The distal portion  204  includes only an intake lumen  214 . Preferably, the proximal portion  202 , the distal portion  204  and the connector  206  are all constructed from silicone, although those skilled in the art will recognize that other suitable biocompatible materials may be used instead. Also preferably, at least the distal portion  204  includes a longitudinal stripe (not shown) having approximately 16% by weight BaSO 4  for opacity. Also preferably, the proximal portion  202  and the distal portion  204  have a hardness of approximately 55 durometer on the Shore Durometer scale, although those skilled in the art will recognize that the proximal portion  202  and the distal portion  204  may have other hardnesses as well. 
   Referring now to  FIGS. 9 and 10 , the proximal portion  202  includes intake and return lumens  210 ,  212 , respectively. The proximal portion  202  includes a proximal end  220  that is releasably connected to a hub  260 , and a distal end  222  that is fixedly connected to the connector  206 , preferably by an adhesive, such as RTV, or other biocompatible adhesive known to those skilled in the art. Alternatively, the distal end  222  of the proximal portion  202  may be molded directly onto the connector  206 . A cross sectional view of the proximal portion  202  is shown in FIG.  10 A. The proximal portion  202  has a preferably circular cross section. Within the circular cross section, the intake lumen  210  is preferably generally oval in cross sectional shape and the return lumen  212  is generally crescent-shaped in cross section, although those skilled in the art will recognize that the intake lumen  210  and the return lumen  212  may be other shapes as well. 
   Referring back to  FIG. 9 , also preferably, the exterior of the proximal end  220  of the proximal portion  202  is coded to identify whether a particular lumen is the intake lumen  210  or the return lumen  212 . Preferably, the code includes a color code, such as a red marking  224  for the intake lumen  210  and a blue marking  226  for the return lumen  204 . Also preferably, at least one, and preferably two, catheter retainer cuffs  228  are disposed about the exterior of the proximal portion  202  between the proximal end  220  and the distal end  222 , and more preferably between the codes  224 ,  226  and the distal end  222 . Also preferably, one of the retainer cuffs  228  is disposed immediately proximally of the connector  206 . Preferably, the retainer cuffs  228  are constructed from a fabric such as DACRON®, although those skilled in the art will recognize that other materials typically used for retainer cuffs may be used. 
   The distal portion  204  includes proximal end  230  that is fixedly connected to the connector  206 , preferably by an adhesive, such as RTV, or other biocompatible adhesive known to those skilled in the art. Alternatively, the proximal end  230  of the distal portion  204  may be molded directly onto the connector  206 . The distal portion  204  also includes an open distal end  232 . Preferably, the distal end  232  also includes an inward spiral of approximately 540 degrees, as is shown in FIG.  9 . While a 540 degree spiral is preferred, those skilled in the art will recognize that the spiral may be more or less than 540 degrees. A cross sectional view of the distal portion  204  is shown in FIG.  10 B. Preferably, the distal portion  204  has a generally oval cross section, although those skilled in the art will recognize that the distal portion  204  may have a cross section of other shapes instead. The distal portion  204  includes a plurality of openings  215  that allow for fluid communication between the intake lumen  214  and the exterior of the distal portion  204 . 
   Referring now to  FIGS. 11A-11D , the connector  206  includes a body  235  that is generally cylindrically shaped. The connector  206  also includes a proximal connector portion  236  that extends proximally of the body  235 . The proximal connector portion  236  includes a generally annular cross section having an interior diameter sized to frictionally accept the distal end  222  of the proximal portion  202 . The connector  206  also includes a distal connector portion  238  that extends distally from the body  235 . The distal connector portion  238  includes an intake portion  239  and a discharge portion  240 . The intake portion  239  is preferably generally oval in cross section and has an interior sized and shaped to frictionally accept the proximal end  230  of the distal portion  204 . As seen in  FIG. 13 , the intake portion  239  is also preferably co-linear with the proximal connector portion  236  to provide a generally straight flow of fluid between the intake lumen  214  of the distal portion  204  and the intake lumen  210  of the proximal portion  202 . 
   Referring to  FIG. 11B , the discharge portion  240  extends through the body  235 , preferably at an angle β relative to the intake portion  239 . Preferably, the angle β is approximately 26 degrees, although those skilled in the art will recognizes that the angle β may be more or less than 26 degrees. Preferably, the discharge portion  240  has a generally oval cross section. The discharge portion  240  allows fluid communication between the interior of the proximal connector portion  236  and the exterior of the body  235 . 
   Referring back to  FIGS. 9 and 10 , a diffuser  242  is disposed over the connector  206 . The diffuser  242  is shown in detail in  FIGS. 12A-12D . The diffuser  242  is preferably constructed from silicone having a durometer of  30 A on the Shore Durometer scale, although those skilled in the art will recognize that the diffuser  242  may be made from other suitable biocompatible material instead. The diffuser  242  includes a generally bulbous body  244  having a hollow interior  245 , a proximal connector portion  246  extending proximally from the body  244 , and a distal connector portion  248  extending proximally into the body  244 . 
   The proximal connector portion  246  has a preferably annular cross section, and has an internal diameter at least slightly smaller than the external diameter of the proximal connector portion  236  of the connector  206  so that the proximal connector portion  246  of the diffuser  242  engages the exterior of the proximal connector portion  236  of the connector  206  in an interference fit. Also, the distal connector portion  248  of the diffuser  242  has a preferably oval shaped cross section, and has an internal diameter at least slightly smaller than the external diameter of the intake portion  239  of the connector  206  so that the distal connector portion  248  of the diffuser  242  engages the exterior of the intake portion  239  of the connector  206  in an interference fit. The elasticity of the material from which the diffuser  242  is constructed allows each of the proximal connector portion  246  and the distal connector portion  248  to expand and frictionally engage respective portions of the connector  206 . 
   Referring to  FIG. 12D , the body  244  of the diffuser  242  also includes a plurality of openings  250  spaced generally radially about an outer perimeter of the body  244 . Preferably, each opening  250  is spaced approximately 60 degrees apart from adjacent openings  250 , although those skilled in the art will recognize that each opening  250  may be spaced more or less than 60 degrees from adjacent openings  250 . The openings  250  extend from the exterior of the body  244  into the hollow interior  245  and allow fluid communication between the exterior of the body  244  and the discharge portion  240  of the connector  206 . The spacing of the openings  250  about the body  244  allow dialysate to diffuse from the discharge portion  240  of the connector  206 , through the hollow interior  245  of the diffuser body  244 , through the openings  250 , and into the peritoneum of the patient during dialysis. Also, the disposition of the openings  250  away from the distal connector portion  248  of the connector  206  and the distal lumen  204  reduce the likelihood of dialysate that is discharged from the openings  250  to flow along the exterior of the distal lumen  204  and back into the catheter  200  before the dialysate has had an opportunity to work. 
   Referring back to  FIG. 9 , the hub  260  includes a proximal portion  262  and a distal portion  264 . The proximal portion includes a first cannula  266  and a second cannula  268  that are sized and shaped to be inserted into the proximal ends of the intake and return lumens  210 ,  212 , respectively, in an interference fit. The first cannula  266  allows for fluid communication between the intake lumen  210  and a first extension tube  270 , having a first luer connection  271 . The second cannula  268  allows for fluid communication between the return lumen  212  and a second extension tube  272 , having a second luer connection  273 . 
   A compression ring  274  is disposed over the proximal ends of the intake and return lumens  210 ,  212  to compress the intake and return lumens  210 ,  212  onto their respective cannulae  266 ,  268 . Preferably, the compression ring  274  is constructed from silicone, although those skilled in the art will recognize that other suitable, biocompatible materials may be used. 
   The distal portion  264  of the hub  260  is slidably disposed over the proximal end  220  of the proximal portion  262  and is threadingly engageable with the proximal portion  202  of the hub  260  to releasably secure the proximal portion  202  to the hub  260 . 
   During manufacture of the catheter  200 , the proximal portion  202  and the distal portion  204  are preferably extruded, as is well known in the art. The diffuser  242  and the connector  206  are preferably constructed by injection molding, as is well known in the art. Preferably, the proximal connector portion  246  of the diffuser  242  is disposed over the connector  206  in a distal to proximal direction so that the proximal connector portion  246  of the diffuser  242  frictionally engages the proximal connector portion  236  of the connector  206  and the distal connector portion  248  of the diffuser  242  frictionally engages the distal connector portion  238  of the connector  206 . The diffuser  242  is fixedly connected to the connector  206 , preferably by an adhesive, such as RTV, or other biocompatible adhesive known to those skilled in the art. 
   Referring now to  FIG. 13 , the distal end  222  of the proximal portion  202  is inserted into the proximal connector portion  236  of the connector  206  such that the intake lumen  210  fluidly communicates with the intake portion  239  of the distal connector portion  238 , and the return lumen  212  fluidly communicates with the openings  250  in the diffuser  242 . The proximal end  230  of the distal portion  204  is inserted into the intake portion  239  of the connector  206  so that the distal portion  204  and the intake lumen  210  are in direct fluid communication with each other, without fluid loss in the connector  206 . 
   The catheter  200  is preferably inserted into the patient in the same manner as described above with respect to the catheters  10 ,  10 ′. 
   Although the invention has been described and illustrated by various embodiments, it will be apparent to those of ordinary skill in the art that changes and modifications could be made, which clearly fall within the scope of the invention. It is understood, therefore, that the invention is intended to be protected broadly within the spirit and scope as defined by the appended claims.