Abstract
Urinothorax, a rare cause of pleural effusion, results from urine accumulation in the pleural cavity due to abnormal communication between the urinary tract and pleural space. It is often associated with urinary tract obstruction, trauma, surgery, or rupture of the renal collecting system. Early diagnosis is challenging because of nonspecific clinical features. We report the case of a 3-year-old male with polymalformative syndrome, right-sided pneumonia, and a history of congenital hydronephrosis, who presented with respiratory distress and decreased breath sounds on the right side of the lungs. Chest X-ray and ultrasound revealed a large right-sided pleural effusion. Thoracentesis yielded turbid fluid, with biochemical analysis showing a high concentration of polymorphonuclear leukocytes and elevated lactate dehydrogenase, consistent with inflammation. Despite this, the large volume of drained fluid exhibited laboratory findings consistent with a transudate. Further imaging demonstrated worsening hydronephrosis with a dilated renal pelvis and right megaureter. A nephrostomy tube was placed, resulting in rapid clinical improvement and resolution of the pleural effusion. This case underscores the importance of considering urinothorax in the differential diagnosis of pleural effusion in children with urinary tract anomalies. Prompt pleural fluid analysis and timely urologic intervention can lead to favorable outcomes.