Transitional cell carcinoma occurring in ureterocele.

A case of transitional cell cancer developing in a ureterocele stump several years after a heminephroureterectomy is described. The role of ultrasonography in establishing the diagnosis is emphasized. This case illustrates the potentially dangerous effect of leaving a defunctionalized ureteral stump and ureterocele. Recommendation is made for removal of the ureteral stump and ureterocele at the time of heminephroureterectomy to prevent the aforementioned complication.