Urinothorax or urothorax, the presence of urine in the pleural space, is a rare complication of percutaneous access to the kidney for the management of complex renal and proximal ureteral calculi and ureteropelvic junction obstruction. Other causes such as blunt renal trauma, ureteral instrumentation, or ureteral surgery have also been reported. The authors describe a patient with a massive left pleural effusion with total lung atelectasis. The diagnosis of urinothorax was confirmed by diuretic renography with Tc-99m diethylenetriamine pentaacetic acid.