- BACKGROUND: Isoperistaltic colon interposition is one of several surgical options available in the treatment of short bowel syndrome. It functions primarily by slowing the rapid intestinal transit that follows small bowel resection (SBR). Previous studies have interposed distal colonic segments and although there is evidence of adaptation by the interposed colon it is not known whether these segments develop histologic or functional small bowel characteristics. METHODS: In this study evidence was sought of metaplasia in the interposed segments after 80% SBR and, because proximal colon is a midgut derivative, the differences between proximal and distal colonic segments were examined. RESULTS: There was no qualitative histological evidence of metaplasia by the interposed segments. There was a significant increase in crypt depth, mucosal thickness and maltase concentration of the interposed segments compared with the nontransposed colon of the controls. The maltase concentations were increased to the extent that they were not significantly different from the concentration present in normal ileum. CONCLUSIONS: Although there was no gross evidence of small bowel intestinalization by the interposed segments, there was evidence of adaptation which was not merely an extension of the adaptive process seen after SBR alone. These changes resulted in the colon taking on some small bowel features. There was no significant difference between proximal vs distal interposed segments.