Case Presentation: A previously healthy 29-year-old woman was diagnosed with end-stage renal disease of unknown etiology and initiated on daily peritoneal dialysis. Patient reported poor compliance with this treatment regimen and, five months later, presented to the emergency department with non-productive cough and pleuritic chest pain. She was found to have left upper lobe pneumonia on initial chest x-ray (Figure 1, left); and peritoneal dialysis was emergently reinitiated for potassium of 7.7 mEq/L. Two days later, patient noted acute onset of worsening shortness of breath and cough, and repeat chest x-ray demonstrated new significant right pleural effusion producing mediastinal shift (Figure 1, right). Workup for infectious, cardiac, respiratory, and neoplastic causes was negative. Thoracentesis was performed; gross appearance was consistent with peritoneal fluid, fluid analysis demonstrated transudative effusion by Light’s criteria, and pleural to serum glucose ratio was four, all suggesting diagnosis of hydrothorax [1]. Given recent initiation of peritoneal dialysis, most likely etiology was related to pleuroperitoneal communication and leak of peritoneal dialysis fluid into the thorax. A permacath was placed by interventional radiology, and patient was transitioned to hemodialysis with initial resolution of pleural effusion. She was discharged with an eight-week course of hemodialysis and outpatient nephrology follow-up for longer-term treatment recommendations.

Discussion: Hydrothorax is a rare but serious complication of peritoneal dialysis, occurring in approximately one percent of cases [2][3]. The cause is related to pleuroperitoneal communication, such as through diaphragmatic defects or pleuroperitoneal fistulas [4]. This complication nearly always presents on the right side due to the porous nature of the right hemidiaphragm [5]. Initial diagnostic evaluation is performed by thoracentesis with pleural fluid analysis, both in physical characteristics and in biochemistry. Definitive diagnosis, though, can be achieved using contrast-enhanced ultrasonography or scintigraphy scan [2][6][7]. First-line, conservative treatment involves cessation of peritoneal dialysis and transition to hemodialysis as necessary. Half of patients achieve resolution after this transition, with interim hemodialysis lasting anywhere from two weeks to eight weeks [4]. A new therapeutic approach has involved continuation of peritoneal dialysis alongside continuous drainage of the effusion with repeated thoracenteses or catheter placement [3]. More invasive procedures can be used—most commonly video-assisted thoracoscopic surgery—but these are not only more restrictive in terms of who is able to perform, but have also been shown to result in non-superior success rate of treatment [4].

Conclusions: Peritoneal dialysis can be complicated by hydrothorax due to the translation of peritoneal fluid through the diaphragm. Standard diagnostic evaluation should include workup of other causes of pleural effusion, as well as gross and biochemical analysis of pleural fluid. While surgical procedures have been shown to be successful in resolution of such effusions, conservative treatment—cessation of peritoneal dialysis, continuous drainage of effusion—is preferred for its lower invasiveness and greater accessibility to patients and providers.

IMAGE 1: Chest x-ray demonstrating emergence of pleural effusion between day 1 (left) and day 3 (right) of hospitalization.