Obstructive migration of renal calculi following cyst aspiration

The authors report 3 cases of ureteral obstruction secondary to puncture of peri-pelvic renal cysts which had been obstructing and dilating the renal pelvis. In each case, non-obstructive calculi passed from the upper collecting system into the ureter or infundibulum within 72 hours of decompression, causing acute renal colic and marked obstruction.