Spontaneous remission of peripelvic renal cysts.

Three cases are presented of spontaneous regression of peripelvic renal cysts. The lesions were manifested by lateral extrinsic pressure defects in the renal pelvis and major calices (all 3 cases), and selective renal angiography showing stretching of vessels plus sharply defined defects in the nephrographic phase (2 patients). In 1 case the mass disappeared following trauma to the flank, while in the remaining 2 cases it disappeared spontaneously.