Experimental carcinogenesis in the resected colon of the rat.

Until now, carcinoma of the large intestine resected previously for benign disease has not been published. However an increasing number of patients resected for Crohn's disease, diverticulitis or trauma may reach nowadays a high lifespan. On the other hand, it is known that the gastroenteral anastomosis is predisposed to cancer development. In this study, the question of whether the large intestine following colotomy or ileotransversostomy is sensitive to carcinogenesis is examined. Male Wistar rats, subjected to colotomy or resection and ileotransversostomy, were treated weekly by subcutaneous injection of 1,2-dimethylhydrazine (12 mg/kg body weight) for seven weeks. The animals were killed 54 weeks after the first injection. At autopsy, 21 out of 29 operated rats had developed adenocarcinomas of the remaining colon. Intact control animals had the same incidence of malignant degeneration of the large bowel. When the anastomosis is chronically irritated by inflammation or by formation of a diverticulum, development, of carcinoma near the stoma was observed. This was the case in three rats of 28 animals. The results demonstrate that the resected colon of the rat is not more sensitive to experimental carcinogenesis than the intact one.