Seromuscular enterocystoplasty in rats.

Enterocystoplasty is commonly used in clinical practice. Many of its undesirable effects, that is infections, stones, mucus production, absorption of urinary components into the blood stream and risk of cancer, result from the intestinal mucosa lining the urinary tract. We report on the feasibility of creating an enterocytoplasty with a seromuscular colonic segment that acquires a transitional epithelial lining. Augmentation enterocystoplasty was performed in 51 male, 500 gm., Sprague-Dawley rats with a 1.82 cm.2 patch of left colon from which the mucosa had been stripped. The serosal surface was used as lining for the enterocystoplasty. The intestinal patch and the bladder capacity at known pressure were measured at operation and at sacrifice. The histology of the enterocystoplasty was studied in detail following sacrifice. Of the animals 40 survived without significant complications and were sacrificed at a mean postoperative time of 30 days (range 5 to 80 days). In the remaining 11 rats a bladder stone developed but it did not seem to affect the outcome of the experiment. The size of the patch could be measured in 22 rats: it was 1.82 cm.2 (standard deviation +/- 0.86) at operation and 2.30 cm.2 (standard deviation +/- 1.1) at sacrifice. In none of the rats did the patch decrease in size. The bladder capacity at a known pressure (mean 17 cm. water) could be measured in 26 animals: it was 2.35 ml. (standard deviation +/- 0.65) at operation and 5.18 ml. (standard deviation +/- 1.19) at sacrifice. Histological analysis was done in 40 rats. In all cases the serosal surface was lined with transitional epithelium, there was no fibrosis or inflammation and the structure of the muscular layer of the bowel remained intact. The earliest growth of uroepithelium in the serosal surface of the bowel was noted at 5 days. This model suggests that the seromuscular enterocystoplasty can be constructed successfully in the rat model. The seromuscular intestinal patch does not shrink. The bladder capacity increases and histology shows a uroepithelial lining of the augmentation.