IMPLANTABLE ARTIFICIAL KIDNEY

Abstract: Implantable artificial kidney formed of biologically inert materials which comprises an outer cover (12) having an inlet (16) for connection to the renal artery, an outlet (18) for connection to the renal vein, and a second outlet (20) for connection to the ureter and which further comprises a zone (22) connected to the renal blood inlet (16) and comprising a blood containing portion and an ultrafiltrate containing portion, the two being separated by a porous wall allowing ultrafiltration therethrough; and a second zone (24) connected to the renal blood outlet (18) which comprises a portion for containing renal blood and a portion for containing the ultrafiltrate separated by a semi-permeable membrane, the portion containing the ultrafiltrate being connected to the outlet (20) to the ureter.

Description: IMPLANTABLE ARTIFICIAL KIDNEY This invention relates to an implaπtable artificial kidney. The kidneys are important excretory organs which amongst other functions produce the urine. Each natural kidney is composed of a large number of microscopic identical sub- units called πephrons. A nephrαn consists of a specially adapted tuft of capilliaries called the glomerulus. Blood passes through the glomerulus and is filtered. The ultra filtrate drains through the tubules leading from the capsule (Bowman's capsule) which encloses the glomerulus. The filtrate then drains from the tubules through collecting ducts into a central funnel of the kidneyIHBLpelvis and thence through the ureters into the urinary bladder. The primary process carried out in the glomerulus is essentially an ultra filtration in which water and dissolved solids leave the blood. The blood loses approximately 20 % of its aqueous content at this stage. This ultra filtrate passes through the tubules where a great deal of the water and some of its solutes are reabsorbed into the blood leaving a concentrated liquid, the urine, which passes through the ureter to the bladder. Approximately 180 1. per day of blood passes through the kidneys producing about 2 1. of urine. When kidneys, through disease or damage, cease to work waste pr-o-chjcts build up in the body leading to illness and certain death within twelve days. Patients with renal failure are currently treated in two ways. The preferred way is the implantation of a healthy kidney supplied from a cadaver and the other method is by periodic dialysis using an external dialysis machine or 'artificial kidney'. Both of these treatments suffer from serious drawbacks. Transplantation of a healthy kidney suffers the disadvantage of the body rejecting 'foreign' organs. Even with the use of anti- rejection drugs, which are not without side effects of their own and cannot be given ad lib, a transplanted kidney cannot be expected to keep the recipient functioning for more than a few years, e.g. five years. Dialysis on an external machine is expensive, inconvenient and seen only as a temporary measure. A patient must spend normally three or four periods of eight to twelve hours each week connected to the machine. A patient will feel unwell both before and after dialysis: before, because of the build up of waste products in the body; and after, because dialysis can upset body chemistry as well as removing too much of the waste products. The present invention is based on the discovery by the inventor that the action of the tubules in allowing the reabsorption of the ultra filtrate is not as complex as has hitherto been thought and, as a result of this, an artificial kidney capable of taking over the functions of a living kidney may be produced which is small enough to be implanted in the patient's body in place of the diseased kidneys. According to the present invention there is provided an im- plantable artificial kidney formed of biologically inert materials which comprises an outer cover having an inlet for connection to the renal artery, an outlet for connection to the renal vein, and a second outlet for connection to the ureter and which further comprises a zone connected to the renal blood inlet comprises a blood containing portion and an ultra filtrate containing portion, the two being separated by a porous wall allowing ultra filtration therethrough; and a second zone connected to the renal blood ou.tlet which comprises a portion for containing renal blood and a portion for containing the ultra filtrate separated by a semi-permeable membrane, the portion containing the ultra filtrate being connected to the outlet to the ureter. Preferably the configuration of the first zone is in the 5 form of concentric tubes wherein renal blood is fed into the central tube and filters through the walls of this into the concentric outer tube . Preferably also, the second zone is also in the form of concentric tubes in this case the ultra filtrate is led into the central tube and water is reabsorb- -,g ed through the semi-permeable membrane back into the blood retained in the concentric outer tube. A cross-over point will be provided between the two zones. Preferably, the materials used in the artificial kidney of 5 the invention are bio-compatible plastics material such as polyethy&rethane (PEU) and polytetrafluoroethane (PTFE). The outer casing or cover is preferably made from PTFE and the tubes comprising the zones are preferably made from PEU. The form of PEU' chosen for the inner tube in both zones 0 is ' such as to have the requisite filtration characteristics, that is allowing filtration (or more properly ultrafiltration) to occur in the first zone but being a semi permeable membrane and 'thus allowing water and certain solutes only to pass in the second zone . 5 In the kidney of the invention the frist zone corresponds to the actions ' of the πephrons and the second zone corresponds to the actions of the tubules that is the ultra filtrate is produced in the first zone and the bulk oftε liquid is then 0 reabsorbed in the second zone and passed back to the blood so that the urine finally produced is relatively concentrated as is the case with a natural kidney. Since the second zone, wherein the ultra filtrate is separated from the blood by a semi permeable membrane, allows substantially only water to pass back into the blood the kidney of the invention may remove certain salutes which it is desired to retain. This can of course be compensated if ever necessary for in other ways, for example in terms of diet or the regular iπgεstioπ of the appropriate compositions in pharmaceutically acceptable forms of solutes. The artificial kidney of the invention, once implanted, will require no maintenance since it relies on no external power source and is .constructed of durable materials. Furhermore, unlike a transplant of a human kidney, there will be no problems of rejection by the -body. Thus it is envisaged that the kidney of the invention will give the recipient completely restored health after renal failure for the natural length of the -patient's life time, in contradistinction to current treatments. The invention will be described, further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a kidney in accordance with the invention; Figure 2 is a cross-sectional view of the internal tubing of the first zone; Figure 3 illustrates the divisoπ of the renal artery to •accommodate a pair of artificial kidneys; and Figure 4 is a partial diagrammatic view of the crossover between the first and secon ' d zones. Referring to the drawings, an implantable artificial kidney generally designated 10 comprises an outer sheath or capsule 12 preferably of PTFE. As illustrated, the outer capsule has a flap 14 therearouπd enabling it to be stitched into position in the body. The kidney 10 contains an entry port 16 for connection to the renal artery, an outlet port 18 for connection to the renal vein, and a urine outlet 20 for connection to the ureter. Within the casing 12 the kidney 10 divides into two zones generally designated 22 and 24 which crossover at 26. In the first zone 22 blood from the renal inlet 16 is fed to a tube 28 (best illustrated in figure 2) which comprises an inner portion 30 and a concentric outer portion 32. The tube 30 is preferably made of PEU and is porous to the extent that it can act as a filter allowing both water and solute to pass therethrough from the blood. The outer 10 tube is preferably made of an impervious material such as PTFE. Blood from the renal artery is fed to the inner tube 30 along which it passes. As can be seen from figure 1 a considerable length of the tube 28 is contained in the first zone 22 by folding the tube so as to use all the available ■JΓ space. As the blood passes along the inner tube 30 water with its accompanying dissolved solids filters through to the concentrically outer tube 32 forming an ultra filtrate. The blood enters at a pressure of approximately 90 mm Hg (owing to the action of the pumping of the heart) and this pressure 0 is quite sufficient to ensure adequate ultra filtration. Once sufficient ultra filtrate has been extracted from the blood, zone 24 is entered by the crossover 26. This is best illustrate in figure 4 from which it will be seen that the inner tube 30 is brought to the outside whereas the outer tube 32 is fed 5 to the centre thus the tubing 34 in the second zone 24 is the reverse con iguration to that in the first zone 22. Furthermore, the character of the tubing changes at the cross-over point 26. Tήe wall of the now inner tube is of a material such as PEU which is of the character necessary 0 to render it a semi permeable membrane that is. of finer pore structure than that needed for the filtration carried out in the first zone 22. Naturally the tubing which is now ' the outer tubing should be impermeable. Thus in the second zone 24 water and solutes from the ultra filtrate is reabsorbed back into the blood which exits to the outlet 18 connected to the renal vein. The solutes which pass back into the blood in the zone depend on the concentration of such solutes in the blood - if the blood is too low in certain solutes, these will automatically pass back through the membrane from the ultra filtrate and so the action is self regulating. The central tube, which by the end of zone 24 now contains urine connects via the outlet 20 to the ureter. Since kidneys are present as a pair, it is likely that the device of the invention will also be used as a pair. Figure 3 illustrates how the renal artery inlet 16 may be divided so as to feed into two sets of tubes 28 in one im- plaπtable artificial kidney. It will be noted that the inlet 16 contains a blood pressure regulating valve 36 which operates only to allow blood into the tubes 28 when the pressure, exceed 75 mm of mercury and acts as a nonreturn valve also. The device of the invention therefore represents a considerable step forward in the treatment of renal failure freeing patients from reliance on external dialysis and problems with rejection of traπsplated live kidneys.

Claims: CLAIMS 1. Implaπtable artificial kidney, ch a r ac ter iz e d i n that it is formed of biologically inert' materials and comprises an outer cover (12) having an inlet (16) for connection to the renal artery, an outlet (18) for connection ,. to the renal vein, and a second outlet (20) for connection to the ureter and which further comprises a zone (22) connected to the renal blood inlet (16) and comprising a blood containing portion and an ultra filtrate containing portion, the two being separated by a porous wall allowing ., n ultra filtration therethrough; and a second zone (24) connected to the renal blood outlet (18) which comprises a portion for containing renal blood and a portion for containing the ultra filtrate separated by a semi-permeable membrane, the portion containing the ultra filtrate being , < - connected to the outlet (20) to the ureter. 2. Implaπtable artificial kidney according to claim 1, ch ar acter ized in - that the configuration of the first zone (22) is in the form of concentric tubes (28) wherein 2 Q renal blood is fed into the central tube (30) and filters trough the walls of this into the concentric outer tube (32), while the second zone (24) is formed of concentric tubes (34) in which the ultra filtrate is led into the central tube and water is reabsorbed through the semi-permeable membrane back 25 into the blood retained in the concentric outer tube and a cross-over point (26) is provided between the two zones (22, 24). 3. Implaπtable artificial kidney according to claim 1, 30 ch a r acter iz ed i n that the materials used i.π the artificial kidney (10) of the invention are bio-compatible plastics materials such as poyethylurethaπe (PEU) and polytetrafluαroethaπe (PTFE). 4. Implantable artificial kidney according to claim 3, character ized in that the outer casing or cover (12) is made from polytetrafluoroethaπe. 5. Implantable artificial kidney according to claim 3, char achterized in that the tubes (28, 34) comprising the zones (22, 24) are made from polyethylurethane.

Inventors: DOBOS-HARDY MATYAS, DOBOS-HARDY, MATYAS
Applicants: PLASTOOL MUEANYAGFELDOLGOZO ES, PLASTOOL MUEANYAGFELDOLGOZO ES SZERSZAMKESZITOE
Application year: 1988
Main classification: A61M1
IPC codes: A61F2, A61M1