Intrathoracic extension of retroperitoneal urine collections.

Five patients with retroperitoneal urine collections (urinomas) had clinical and radiographic evidence of intrathoracic disease. All five patients rapidly accumulated pleural fluid, documented chemically in three patients to be urine. Two patients developed acute mediastinal widening which rapidly cleared after surgical drainage of the retroperitoneal urinoma. Although rare, thoracic collections of urine should be considered when pleural effusions or mediastinal widening occur in patients with urinary tract obstruction or retroperitoneal urinomas.