Hunt for the Shunt: An Unusual Case of Late-onset Hydrothorax in a Patient on Peritoneal Dialysis.

Hydrothorax is a rare complication of peritoneal dialysis occurring in about 2% of continuous ambulatory peritoneal dialysis (CAPD) patients. These effusions occur soon after the onset of dialysis and are usually right-sided. We describe an unusual case of late-onset, left-sided, and recurrent effusions in the setting of CAPD. A 67-year-old patient with end-stage renal disease on CAPD for the last three years was admitted to our hospital with acute hypoxic respiratory failure secondary to a left-sided effusion. Although previously asymptomatic, he had three admissions for bilateral (left predominant) effusions in the last year, all of which were found to be transudative on analysis. Therapeutic thoracentesis once again revealed a transudative effusion with an elevated pleural fluid-serum glucose gradient. On this occasion, pleuro-peritoneal scintigraphy with technetium-99m was performed, uncovering a communication between the peritoneal cavity and the left pleural cavity. The peritoneal dialysis was substituted with hemodialysis, and the patient showed an eventual resolution of left-sided effusions within 18 months. Hydrothorax in peritoneal dialysis is due to the transudation of fluid across congenital or acquired pleuro-peritoneal communications. Pleural fluid with protein content less than 3 g/dl, high glucose, and low lactate dehydrogenase (LDH) relative to blood, and the presence of both D and L isomers of lactic acid suggest a transdiaphragmatic leak. Early diagnosis via peritoneal scintigraphy and appropriate management can prevent significant morbidity and mortality.