Overhydration May Be the Missing Link between Peritoneal Protein Clearance and Mortality

Peritoneal protein loss (PPL) has been associated with mortality. Inflammation was assumed a putative cause with malnutrition as a consequence. Hydrostatic convection is a major drive for microvascular protein transport, but most studies in peritoneal dialysis (PD) patients overlooked this mechanism. An association between peritoneal protein clearance (PPCl) and venous congestion has been reported recently. The aim of this study was to explore the importance of fluid overload in PPCl in PD.

Sixty-seven prevalent PD patients were assessed with peritoneal equilibration test and multifrequency bioelectrical impedance assessment (BIA). PPL and PPCl were calculated from simultaneously obtained 24-h peritoneal effluent.

PPL averaged 5.2 g/24 h. It was higher in patients on continuous treatment than in those without a long dwell. Significant associations between PPCl and BIA parameters of overhydration were found in both univariable and multivariable analyses. Lean mass index, partly dependent on hydration status, was associated with PPCl in univariable but not in multivariable analysis. A multiple linear model identified extracellular water excess and higher D/P creatinine as predictors of higher PPCl, independent of PD duration, type of PD, age, gender, albumin, cardiovascular disease, C-reactive protein, or lean mass index.

The uni- and multivariable strong associations between fluid overload and PPCl support the importance of hydrostatic pressure-induced convection for PPCl. Also, peritoneal small solute transport was associated with PPCl. Both are amenable by adjusted dialysis prescription, especially focused on fluid status and avoidance of overhydration. The assumption of an association with inflammation and malnutrition was not confirmed.