Nitrosamine-induced colonic carcinogenesis in rats after jejuno-ileal bypass.

In the present experiment the influence of the exclusion of approximately 50% of the small bowel on chemically induced colonic carcinogenesis was investigated. For tumor induction the nitrosamine derivative acetoxymethyl-methyl-nitrosamine was applied intrarectally weekly for 8 weeks in 72 male Sprague-Dawley rats. The animals were randomized into 3 groups; in one group, small bowel exclusion was performed before the tumor induction, in the other group after the induction period. The control group received explorative laparotomy only. Tumor development was examined endoscopically and at autopsy 40 weeks after the start of the experiment. No differences occurred regarding number, shape and size of tumors in the operated versus the control group.