Effects of small bowel transection, resection, or bypass in 1,2-dimethylhydrazine-induced rat intestinal neoplasia.

The incidence, distribution, size, and histopathology of rat small and large bowel tumors induced by sequential administration of 1,2-dimethylhydrazine followed by either small bowel resection, 50% jejunoileal resection, or 50% jejunoileal bypass were examined in addition to measurements of transit times and beta-glucuronidase activities in large bowel contents. The results indicate that even limited small bowel resection or bypass promotes intestinal neoplasia, particularly in the large bowel, and this effect seems independent of the chronic injury imposed by suture lines. Although no differences in transit times were observed, increased beta-glucuronidase activities in both cecum and distal colon of resected but not bypassed rats was detected. Moreover, an apparent subsite redistribution of small bowel tumors to ileum and large bowel tumors to more proximal colon in bypassed rats suggests that the mechanisms involved for tumor enhancement differ substantially from those in resected rats.