The use of computed tomography in the diagnosis of carcinoma of the renal pelvis causing ureteropelvic junction obstruction.

The computed tomographic (CT) appearance of 5 cases of primary malignancy of the renal pelvis causing ureteropelvic junction (UPJ) obstruction is presented. The tumors appeared as enhancing thickened, nodular, and crescentic masses at the UPJ. Comparison is made to the thin, regular wall of the hydronephrotic pelvis caused by congenital UPJ obstruction. Differentiation from other causes of UPJ obstruction by CT is discussed. A CT scan is particularly valuable when the cause of UPJ obstruction remains elusive after urography and pyelography.