Morphology in the cat ileal mucosa following construction of an ileal reservoir or transposition of patches to different locations.

In an attempt to examine the response of the ileal mucosa to different noxious environments and to correlate the results with findings in human continent ileostomy reservoirs, cat intestine was subjected to various operative procedures: first, ileal reservoirs were constructed in continuity with the small intestine, a technique that was slightly different from that employed in human subjects, and secondly, segments or patches of ileum were transposed to the colon, the urinary bladder, or the jejunum. Morphometric evaluation was subsequently performed on these samples. The mucosa of the reservoir revealed a decrease in villus height accompanied by an increased mitotic index. Identical changes were observed when ileal segments or patches were inserted in the colon, whilst transposition to the urinary bladder resulted in similar but more pronounced alterations. When ileal patches from the colon or urinary bladder were replaced in the jejunum, the villi were once again enlarged. The epithelial cells remained normal in all cases except following transposition to the urinary bladder, where flattening of the cells or partial denudation of the villus tips was encountered. The changes observed represent a classical hyper-regenerative transformation of the mucosa, and correspond closely with the changes recorded in human continent ileostomy reservoirs. Furthermore, the reversibility of such alterations has been demonstrated. The experimental design permitted the exclusion of intraluminal pressure, dilatation, and nervous and vascular derangements as the cause of the transformation; it is concluded that the intraluminal environment is the factor most probably responsible for such structural alterations.