Effects of anticoagulation and ileal resection on the development and spread of experimental intestinal carcinomas

The possibility that anticoagulation with warfarin might inhibit the development of spontaneous metastases from intestinal carcinomas induced by azoxymethane (AOM) was tested in Sprague-Dawley rats with and without 60% distal small-bowel resection (DSBR). Warfarin (0.5 mg/l) was added to the drinking water from 1 week or 12 weeks postoperatively, and thromboplastin times were measured thereafter. AOM was given by 12 weekly s.c. injections (10 mg/kg/week), starting 1 week after DSBR. Besides increasing the sensitivity of rats to warfarin, DSBR itself caused partial anticoagulation, probably because of vitamin K malabsorption: at 30 weeks faecal fat was 59-93% higher, while serum B12 was 40% lower (> 0.05 P > 0.005). Adaptive growth of the jejunum and caecum after DSBR was manifested by 22-76% increases in segmental weight and surface area (P < 0.001). DSBR produced a 4-fold increase in duodenojejunal tumours at 15-25 weeks (P = 0.025) and a 76% increase in colorectal tumours at 25-35 weeks (P < 0.005). Eight of 20 control rats dying after 15 weeks had lymphatic metastases, compared with 0 of 15 rats with DSBR plus warfarin from week 1 (P = 0.005). The overall prevalence of metastases was reduced by both DSBR and warfarin, when assessed independently. Intestinal carcinogenesis induced by AOM is enhanced by the adaptive response to DSBR, but anticoagulation inhibits spontaneous metastases in this model.