Recurrent pleural effusion during peritoneal dialysis: answer

Abstract

Answers1. Leakage of peritoneal dialysis (PD) fluid into thepleural cavity.2. Measurement of the glucose concentration in thepleural effusion.3. Very high intrathoracic pressure during mechanicalventilation for acute respiratory distress syndrome(ARDS) transiently prevented leakage of PD fluid intothe pleural cavity. Reduction of ventilator settingsunmasked the pleuro-peritoneal connection with PDfluid leaking through the incision site.4. To decrease PD dwell volume or temporarily discontinuePD and switch to hemodialysis / hemofiltration.CommentaryHydrothorax - mostly on the right side - is a well-knowncomplication of PD, which is observed in approximately2% of all PD patients [1]. In our patient, the glucoseconcentration in the pleural fluid obtained in the firstpuncture was 24.9 mmol/L (452.7 mg/dL), in the fluiddraining from the insertion site four weeks later this was20.5 mmol/L (372.7 mg/dL). Her blood glucose levels werearound 10 mmol/L (180 mg/dL) during the time of the firstpuncture and around 7 mmol/L (126 mg/dL) on the secondoccasion. Thus, the intrapleural glucose concentrationgreatly exceeded the serum values. This finding can onlybe explained by leakage of PD fluid into the pleural cavity,which ceased transiently during high-pressure ventilation.With these ventilator settings, the intrathoracic pressureexceeded the intraaabdomial pressure thereby preventingperitoneal-pleural shunting.Usually, demonstration of high glucose concentrations inthe pleural fluid is sufficient to confirm a peritoneal-pleuralleak [2]. In ambiguous cases - or if no pleural puncture isdone - peritoneal-pleural shunting can be demonstrated byadding a radioactive tracer to the dialysate [3, 4]. Although2 - 4 times higher than the serum concentrations, theintrapleural glucose concentration was still significantlylower than the glucose concentration in the PD fluid, whichwas 137.5 mmol/L (2475 mg/dL). This reflects incompleteequilibration between the fluid collections in both compart-ments due to inconstant shunting or a small communicationbetween both cavities.Leakage of PD fluid into the pleural cavity has to bedifferentiated from other causes of transudative pleuraleffusionsuchascongestivecardiacfailure,hypoalbuminemia,or fluid overload. In the latter conditions, ultrafiltration ispreserved and can typically be increased by using higherPD fluid glucose concentrations. Pleural effusions from aperitoneal-pleural leak typically do not improve with thisintervention. In this respect the present case is atypical asultrafiltration was preserved and could be increased afterswitch to a higher PD fluid glucose concentration.