Functional and structural studies of ileal reservoirs used for continent urostomy and ileostomy

The structure and function of the mucosa has been studied in continent ileostomy and urostomy reservoirs, the latter being a receptacle for diverted urine constructed out of ileal tissue. Morphometric evaluation was performed by a microdissection technique and functional studies involved the assessment of L-phenylalanine absorption by the whole pouch in vivo and the uptake of the same amino acid by biopsy samples in vitro. Endoscopic examination revealed fairly homogeneous villous structure in the ileostomy reservoirs. In the urostomies, there was a gradual appearance, as a function of the postoperative time interval, of areas of flat mucosa intermingled with villous regions. When possible, biopsies of the two types of mucosa were studied separately. Even in the villous regions of the urostomies, the size of the villi was smaller in all dimensions than the villi of ileostomy samples. The uptake of phenylalanine in vitro, however, was the same in villous samples from urostomies and in ileostomy biopsies. The absorption of phenylalanine in vivo by the whole pouch was lower in the urostomies. There was a good correlation between amino acid absorption in vivo and in vitro in the ileostomies, but not in the urostomies. This is attributed principally to the variable proportions of avillar and villous mucosa in the latter material, as there is a clear reduction in absorption in vivo in the longest established urostomy pouches.