Circumferential perirenal urinoma mimicking nephromegaly on urography.

Four cases of circumferential perirenal urinoma in patients with cancer are described. Intravenous urography showed evidence of apparent renal enlargement. In 1 case, opacification of extravasated urine was dense enough to be seen on the urogram, and the diagnosis was confirmed by computed tomography (CT). In the other cases, sonography followed by CT diagnosed urinoma, after tumor invasion had been suggested because of the pseudonephromegaly. Ureteral obstruction was demonstrated in all cases, due to retroperitoneal adenopathy in 1 case and to pelvic tumor in the other 3. Sonography or CT is required for the diagnosis of circumferential perirenal urinoma mimicking nephromegaly urographically.