Urothelial carcinogenesis and portocaval anastomosis in the rat

Portacaval anastomoses were performed in the rat to study urothelial carcinogenesis in this model and the promoting effect of dietary tryptophan. We were unable to produce any urothelial cancers or premalignant changes; some animals formed uric acid stones and developed papillary hyperplasia in the bladder. We conclude that the initiating carcinogen is likely to be exogenous and may be dietary in those experiments that have produced urothelial cancers.