CONTRASTING EFFECTS OF SUBTOTAL ENTERIC BYPASS, ENTERECTOMY, AND COLECTOMY ON AZOXYMETHANE-INDUCED INTESTINAL CARCINOGENESIS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (3) , 538-543
Abstract
Compensatory hyperplasia after extensive loss of functioning small or large intestine might predispose to the development of neoplasia in the residual adapted bowel. To test this hypothesis, male Fischer rats were randomized to receive 85-90% jejunoileal resection or bypass, subtotal colectomy or no operation (controls). One week later, the first of 6 weekly s.c. injections of azoxymethane (15 mg/kg per wk) was given. At the 36th week postoperatively, mean body weight after enteric bypass was 62% of control values and after enterectomy or colectomy it was 78-79% of control. Adaptation after all 3 operations was characterized by 22-84% increments in villous height and crypt depth in the residual fucntioning ileum (P = 0.05-0.001); the depth of colonic crypts was unchanged. Fewer rats developed intestinal tumors after enteric bypass (36%) than after any of the other treatments (80-91%) (P = 0.01-0.001). Compared with controls, bypass reduced the number of colonic tumors by 77% (P < 0.001). Although resection did not affect colonic tumor yield, it tripled the incidence of tumors in the duodenum and jejunum (P = 0.025). Colectomy promoted rectal carcinogenesis (P < 0.05). Anastomotic tumors were more common after intestinal resection. The lower frequency of tumors after jejunoileal bypass contrasts with enhanced carcinogensis after enterectomy or colectomy. Profound reduction in body weight may prevent the promotional effect of adaptive hyperplasia.