Extrarenal pelvic hydronephrosis: report of five cases.

Five patients are reported with uretropelvic obstruction and hydronephrosis in which the renal pelvis is predominantly involved. Because of the extrarenal position of the pelvis in these patients, its dilatation is apt to cause distortion and displacement of the calyces and infundibulae simulating an intrarenal mass. Calyceal and infundibular dilatation is much less apparent and general renal outline and cortical thickness is better preserved in these patients than in those with classical hydronephrosis. Careful attention to radiographic technique including delayed films, ultrasonography and occasional arteriography should prevent any confusion with a solid mass lesion.