Urinothorax as an unusual type of pleural effusion - clinical report and review

Despite the fact that there are a great number of established etiologies for pleural effusion, there are grounds for believing that there are also causes from unusual pathophysiological mechanisms, seen in certain clinical contexts and from potential iatrogenic interventions. Urinothorax is such a rare type of pleural effusion as there are fewer than 70 cases reported worldwide.

A patient with a persistent left pleural effusion was admitted to the Urology ward for a lithiasic obstructive uropathy with hydronephrosis. A left percutaneous nephrostomy was performed. The effusion was unclassified at the initial workup and recurred after first drainage. A second approach confirmed a citrine fluid with borderline criteria for exudate, ammoniacal odour and an elusive pleural fluid-to-serum creatinine ratio. A retroperitoneal urinoma was recognized on CT, and the patient underwent a left nephrectomy with resolution of the pleural effusion.

Urinothorax most frequently develops in patients with excretory uropathy or blunt abdominal trauma, although other mechanisms have been reported. Traditionally, a pleural fluid to serum creatinine ratio higher than one is a hallmark of this condition. In certain settings, taking this diagnosis into account at an early stage might be crucial for a good outcome.