Rat colonic carcinogenesis after ureterosigmoidostomy: pathogenesis and immunohistological study.

A group of 44 rats underwent the equivalent of a ureterosigmoidostomy (US), while a second group of 18 rats underwent a pediculated graft (PG) of urothelial tissue in the sigmoid wall. Histological lesions were observed in the colon near the bladder colon junction in US rats exclusively. These lesions included dysplasias (5/23), cystic glands (4/23) and 10 neoplasms (9/23), three of which were adenomas, showing elements of juvenile polyp and tubular adenoma in one case. The seven other tumors showed typical histological features of colonic adenocarcinomas, but no frank evidence of parietal tumoral invasion was observed and their cancerous nature was questionable. It is probably a true carcinogenesis since we induced the same histological changes as those in the mucosae adjacent to colonic adenocarcinomas after human US surgery. Moreover, by immunoperoxidase using antibodies against mucus associated antigens (M1 and M3C antigens) we demonstrated that US rat carcinogenesis differs from dimethylhydrazine (DMH) rat carcinogenesis. Furthermore, our results suggest that urine may be an important factor in inducing this type of US carcinogenesis.