Hydrothorax secondary to pleuro-peritoneal communication can develop as a complication of peritoneal dialysis. Patients present with poor ultrafiltration from peritoneal dialysis and shortness of breath. The effusion is mostly on the right side. It does not improve with hypertonic peritoneal exchanges. Diagnostic tapping reveals a sterile, transudative effusion with a high glucose content (due to the glucose-containing dialysate).