The Use of Pleural Fluid to Serum Glucose Ratio in Establishing the Diagnosis of a Not So Sweet PD-Related Hydrothorax: Case Report and Literature Review

Hydrothorax is a well-known but rare complication of peritoneal dialysis (PD), with an average incidence of 2% mainly in cases of continuous ambulatory peritoneal dialysis (CAPD). In more than 80% of these cases, the hydrothorax is attributed to an abnormal pleuroperitoneal communication. It commonly manifests as unilateral effusion, predominantly on the right. A thoracentesis to determine pleural glucose has been a diagnostic aid well relied on, as the dextrose rich dialysate raises the pleural fluid glucose. A pleural fluid glucose to serum glucose gradient greater than 50 mg/dL is suggestive of a leak with a specificity of 100% according to some studies; however, its sensitivity is variable. Our case illustrates a diagnostic dilemma due to a relatively low pleural fluid to serum glucose gradient of 21 mg/dL that caused a delay in diagnosis. A pleural fluid to serum glucose ratio >1.0 was used as a diagnostic marker that pointed toward a peritoneal leak. For confirmation, a peritoneal scintigraphy with nuclear technetium 99 scan was performed that revealed a pleuroperitoneal fistula as the source of the recurring hydrothorax in the setting of automated peritoneal dialysis (APD). The hydrothorax completely resolved with termination of APD on follow-up as the patient was transitioned to intermittent hemodialysis (HD).