Unilateral urinothorax can occur contralateral to the affected kidney.

Urinothorax is a rare cause of transudative pleural effusion with biochemical characteristics of urine, usually secondary to obstructive uropathy. Urine usually moves into the pleural space from the retroperitoneal or peritoneal space via diaphragmatic lymphatics or an anatomical diaphragm defect. A total of approximately 70 cases have been previously described in the literature, and in the vast majority of cases urinothorax is unilateral and ipsilateral to the side of obstructive uropathy, trauma or malignancy. This report describes a rare case of unilateral urinothorax occurring contralateral to the side of obstruction.