Pleural effusion and hydronephrosis in a newborn.

While the association of obstructive uropathy with ascites has been known since 1863, and with pleural effusion since 1954, the latter combination remains rare. This case report describes a male newborn with a massive left pleural effusion that was caused by same-sided hydronephrosis from obstructing posterior urethral valves. The effusion disappeared within a few days after adequate urinary drainage was established, and the infant was remained well since the abnormal urethral valves were fulgurated cystoscopically. Review of the clinical and experimental literature reveals no consensus about how pleural fluid accumulates in the presence of obstructive uropathy, and this neonate showed a direct inverse relation between the amount of pleural fluid drainage and urinary output via catheter. Hydronephrosis should be considered diagnostically when a newborn has a pleural effusion that is otherwise unexplained.