Experimental colonic carcinogenesis: changes in faecal bile acids after promotion of intestinal tumours by small bowel resection in the rat.

Small bowel resection promotes the development of colonic tumours in azoxymethane treated rats. As high faecal bile acid concentrations are associated with colonic cancer and may be altered by resection, we have studied changes in faecal bile acid concentrations during promotion of colonic carcinogenesis by increasing small bowel resection. Twenty rats in each group underwent either jejunal transection or 20%, 50%, or 80% proximal small bowel resection. Tumours were induced with azoxymethane 10 mg/kg by 12 weekly subcutaneous injections, and faecal bile acid concentrations were measured at six and 16 weeks. Colonic tumour number rose from 0.6 per rat in the transection group to 1.6 per rat in the 50% resection group (p less than 0.01) but were not significantly different to transection values at 0.8 per rat in the 80% resection group. Total daily faecal bile acid excretion and bile acid concentrations fell with increasing resection from 14.2 (1.6) mg/rat/day and 5.8 (0.7) mg/g dry faeces respectively in the transection group to 6.5 (0.5) mg/rat/day and 2.9 (0.2) mg/g respectively in the 80% resection group (p less than 0.001). The greatest reduction was seen in the concentration of deoxycholic acid which has been particularly associated with the aetiology of colonic cancer. The promotion of colonic tumours following small bowel resection in carcinogen treated rats is unlikely to be mediated by changes in faecal bile acid concentration or composition.