Obstructive renal cysts.

Renal cysts usually are asymptomatic, produce no harm to the kidney and require no treatment once diagnosed. However, an occasional expanding cyst causes progressive obstruction to caliceal or pelvic outflow. Herein is reported observations on 4 patients in whom cysts produced significant obstruction to the pelvic or major caliceal outflow. In 3 cases treatment was by decompression, with resolution of the obstruction. Two requirements must be met for a cyst to obstruct: 1) it must lie at or near the hilus and 2) it must have turgor sufficient to overcome the pressure of the intrapelvic urine. In contrast to most renal cysts those producing significant obstruction require operation.