A Prosthetic Urinary Bladder—Why Not?

Editorial A Prosthetic Urinary BladderWhy Not?

Table I.-Ideal Characteristics of a Prosthetic Bladder Bonds biologicallywith the urethra, ureters, and intestine Provides adequate volume (200-500 ml) Allows complete, volitionalevacuationof urine-preferably through the urethra Is tolerant of intraluminalbacterial colonization Is resistant to extraluminalbacterial infection Reliably drains the upper urinary tract Is mechanicallyreliable Requires simple, inexpensivemaintenance

After cystectomy, bladder function is replaced with conduits and pouches constructed from autogenous bowel segments. These methods work reasonably well but not ideally. Development of a totally alloplastic "artificial urinary bladder" has been an elusive goal of many experimental and clinical investigators. The ideal characteristics of an artificial bladder and some of the engineering problems that must be addressed are summarized in Tables I and 2, respectively. Prosthetic alloplastic materials may be used to augment (for example, "patch") the native bladder or to replace it completely. Bladder "patches" are suboptimal. Porous alloplastic patches successfully bond with detrusor muscle and thereby increase bladder capacity for short-term function. Within a year, however, such patches are extruded intraluminally, where they become encrusted with stone-forming minerals. Numerous experimental investigations attest to this common result. 1 Complete replacement of the urinary bladder is possible through use of either a "distensible-volume model" or a "fixed-volume model." The distensible-volume reservoir attempts to mimic the human model, whereas the fixedvolume model replaces the human model with a simple, rigid wall reservoir," Distensible-Volume Model-Distensible-volume reservoirs demand complex filling and emptying mechanisms that use both positive and negative pressures. In this issue of the Mayo Clinic Proceedings (pages 215 to 220), Barrett and coauthors describe a new design for a distensible model. Their model uses sophisticated hydraulic mechanisms to create negative intrareservoir pressures during filling and positive intrareservoir pressures during evacuation. Other investigators have studied less sophisticated distensible models in various animal species (Table 3) and have reported only limited success. In most of the recent reports, the distensible reservoir was attached to the ureters and urethra by using Dacron-reinforced intubation. Alloplastic tubes inserted into the ureters and urethra invariably elicited an inflammatory mucosal reaction that resulted in formation of an intraluminal papilloma. The papilloma almost always caused substantial obstruction. Barrett and associates seek

Allows convenient"control" of intraluminal bacterialcolonization Is cosmeticallyand functionally more attractivethan other alternatives Is associated with few side effects and complications

to remedy this problem by use of hollow "double J catheters" inserted into the renal pelves. As with other models, "watertightness" will be achieved in this artificial bladder by using Dacron-reinforced anastomoses to the ureter and urethra, albeit with the double J spirals lying in the renal pelves; thus, formation of an intraluminal papilloma is avoided. Fixed-Volume Model-In the alternative prosthetic model (that is, the fixed-volume reservoir), a vent to ambient air is needed. The vent must incorporate an air-permeable, Table 2.-Engineering Problems Associated With a Prosthetic Bladder Parts of the urinary bladder are mobile Alloplasts bond poorly to mobile tissues Urine is saturated with minerals that can crystallize and encrust foreign bodies Foreign bodies harbor and perpetuatebacteriuria Encrusted foreign bodies grow into stones and can obstruct urinary passages Urine is an excellent growth medium for bacteria Bacterialcolonizationof bladder urine is common

Address reprint requests to Dr. D. P. Griffith, 6560 Fannin, Suite 1004, Houston,TX 77030. Mayo Clin Proc 67:293-295, 1992

Bacteria-colonized urine incites inflammatory changes in adjacent tissues Urease-producing bacteria cause struviteencrustationand struvite stones Bacteria block fibroblasticingrowthinto alloplasticmaterials Alloplasts can cause local or systemicside effects months or years after implantation

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EDITORIAL

Table 3.-Summary of Distensible-Volume Artificial Urinary Bladder Models Material

Year

Investigators

Model

No.

Result*

Silicone rubber with Marlex cuff

1964

Friedman et af

Dog

8

100% hydronephrosis; 20% "leak"

Silicone rubber with Rhodergon cuff

1976

Auverr'

Dog

8

FU 1-12 mo; urethral fistulas common; hydronephrosis common

Silicone rubber with Rhodergon cuff

1977

Abbou et aJS

Dog

10

FU 2 mo; intubation of urethra and ureters; 40% hydronephrosis; poor emptying

Silicone rubber with Dacron cuff

1981

Apoil et al6

Dog

12

FU 16 mo; hydronephrosis common; urethral leaks common

Silicone rubber with Dacron cuff

1984

Barrett & Donovan?

Dog

5

Problematic filling and emptying; 80% hydronephrosis at 3-5 wk

Silicone rubber with Dacron cuff

1985

Pentermann et al"

Dog

2

FU 18 days; no hydronephrosis; no extravasation

Silicone rubber (? cuft)

1987

Hannappel et al?

Sheep

12

FU 12 mo (few details); no hydronephrosis; no extravasation

*FU = follow-up.

water-impermeable membrane to allow air to flow out of the reservoir during filling and to allow air to flow into the reservoir as urine is evacuated. A possible prototype is shown in Figure 1. It would fill by pyeloureteral peristalsis

Conduit - prosthesis anastomosis Abdominal stoma and filter

-J~~~~~~t/f(

Reservoir in erect position

Fig. I. Diagram of rigid wall, fixed-volume reservoir for urinary bladder prosthesis. Transcutaneous stomal cap contains a replaceable air-permeable, water-impermeable membrane. Transcutaneous and anastomotic components of the silicone rubber reservoir are bonded with porous alloplasts to achieve watertight unions. An endoscopically exchangeable "urethral valve" could be placed at bladder outlet. (From Gleeson and associates.' By permission of Baylor College of Medicine.)

(4 to 15 em Hp pressure) and would evacuate, through the urethra, by gravity drainage inasmuch as the intravesical pressure would always be zero. The reservoir might be implanted concurrently with performance of a cystectomy and creation of an ileal conduit. In a later stage, the conduit might be anastomosed to the "bladder" to activate the in situ reservoir. The fixed-volume model with a transcutaneous abdominal stoma would facilitate endoscopic access to the prosthesis and would allow endoscopic placement of an electronically activated "urethral valve" within the reservoir; the valve could be controlled with a hand-held transmitter, similar to a garage door opener. The transcutaneous stoma allows addition of pharmaceuticals. In addition, an iontophoretic device and a volume sensor with an audio alarm can be incorporated into the vent cap (Fig. 2). Iontophoresis (that is, microampere quantities of direct electrical current) has been shown to eliminate urinary infectionlO,ll-particularly infections associated with prosthetic devices. 12 Conclusion.-Both the distensible-volume model and the fixed-volume model of artificial urinary bladders warrant additional investigations. The vast array of available or proposed intestinal pouches and reservoirs is an indication that ideal urinary bladder replacement has not yet been demonstrated.

Donald P. Griffith, M.D. Malachy J. Gleeson, M.Ch. Scott Department of Urology Baylor College of Medicine Houston, Texas

Mayo Clin Proc, March 1992, Vol 67

EDITORIAL

Top View

Volume sensor w/audlo alarm

Iontophoretic battery & aleclronlc chip

Volume sensing eleclrode Intr&-raservolr catheter

Fig. 2. Diagram of cap for transcutaneous abdominal stoma. Cap incorporates a volume sensor with audio alarm, an iontophoretic device, and an air-permeable, water-impermeable membrane.

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REFERENCES 1. Griffith DP, Gleeson MJ: The prosthetic bladder. In The Bladder. Edited by J Fitzpatrick, R Krane. London, Churchill Livingstone (in press) 2. Gleeson MJ, Anderson S, Homsy C, Griffith DP: Experimental development of a fixed volume, gravity draining, prosthetic urinary bladder. ASAlO Trans 36:M429-M432, 1990 3. Friedman B, Smith DR, Finkle AL: Prosthetic bladder of silicone rubber in dogs. Invest Urol 1:323-338, 1964 4. Auvert J: Trends in alloplastic replacement of segments of the urinary tract. Urol Res 4:143-145,1976 5. Abbou C, Leandri J, Auvert J, Rey P: New prosthetic bladder. Trans Am Soc ArtifIntern Organs 23:371-374,1977 6. Apoil A, Granger A, Sausse A, Stern A: Experimental and clinical studies of prosthetic bladder replacement. In Genitourinary Reconstruction With Prostheses. Edited by LV Wagenknecht, WL Furlow, J Auvert. Stuttgart, Germany, Georg Thieme Verlag, 1981, pp 75-80 7. Barrett DM, Donovan MG: Prosthetic bladder augmentation and replacement. Semin Urol 2:167-175, 1984 8. Pentermann EJ, Kambic H, Matsushita M, Kay R, Nose Y: Prerequisites for urinary bladder design. Trans Am Soc Artif Intern Organs 31:308-312,1985 9. Hannappel J, Rohrmann D, Heinrichs B, Gerlach R, Schafer W, Lutzeyer W: Long-term results from artificial bladder implantation in animals (abstract). J Urol 137 (Suppl): 107A, 1987 10. Davis CP, Arnett D, Warren MM: Iontophoretic killing of Escherichia coli in static fluid and in a model catheter system. J Clin Microbiol 15:891-894,1982 11. Davis CP, Wagle N, Anderson MD, Warren MM: Bacterial and fungal killing by iontophoresis with long-lived electrodes. Antimicrob Agents Chemother 35:2131-2134,1991 12. Costerton JW: The bacterial biofilm in nature and disease. Presented at the 86th Annual Meeting of the American Urological Association, Toronto, Ontario, Canada, June 2 to 6, 1991