Morphologic and functional alterations of intestinal segments following urinary diversion.

The current study was undertaken to determine the effect of chronic urinary diversion on both the morphology and absorptive function of intestine. Adult female Wistar rats (N = 8) underwent urinary diversion by interposing a 10-12 cm. segment of distal ileum between the bladder and sigmoid colon following urethral ligation. Control animals (N = 8) underwent sham laparotomies. Three months later, the diverted segment and a 10-12 cm. segment of distal ileum in control animals were studied. The intestinal segments were studied morphologically by both light microscopy and transmission electron microscopy. By using a previously reported in vivo intestinal perfusion model, the transport properties of the intestinal segments were examined. There were prominent and consistent morphological alterations in the diverted segments when compared with normal ileum. These changes consisted of marked mucosal atrophy evidenced by loss of microvilli with decreased villi-to-crypt ratio in diverted segments. Diverted ileum secreted more sodium and absorbed less chloride than normal ileum though this difference was not statistically significant. Water flux into the intestinal lumen was higher in diverted bowel (p = .06). The absorption of ammonium, potassium, and urea, as well as bicarbonate secretion, was the same in the diverted ileum as in normal ileum. There was also no significant difference in pH change or osmolar flux between the two groups. In conclusion, the results of this study indicate that despite morphological changes as a result of chronic exposure of urine, intestinal segments continue to transport urinary solutes similar to normal nondiverted segments. This represents the first convincing evidence that the reason for the low incidence of metabolic alterations following urinary diversion is not due to decreased absorptive capacity of the intestinal mucosa.