Peritoneal Protein Losses Depend on More Than Just Peritoneal Dialysis Modality and Peritoneal Membrane Transporter Status.

Peritoneal protein clearance (PPCl) depends upon vascular supply and size selective permeability. Some previous reports suggested PPCl can distinguish fast peritoneal membrane transport due to local or systemic inflammation. However, as studies have been discordant, we wished to determine factors associated with an increased PPCl. Consecutive patients starting peritoneal dialysis (PD) who were peritonitis-free were studied. Data included a baseline peritoneal equilibration test (PET), measurement of dialysis adequacy, 24-h dialysate PPCl and body composition measured by multifrequency bioimpedance. 411 patients, mean age 57.2 ± 16.6 years, 60.8% male, 39.4% diabetic, 20.2% treated by continuous ambulatory peritoneal dialysis (CAPD) were studied. Mean PET 4-h Dialysate/Serum creatinine was 0.73 ± 0.13, with daily peritoneal protein loss 4.6 (3.3-6.4) g, and median PPCl 69.6 (49.1-99.6) mL/day. On multivariate analysis, PPCl was most strongly associated with CAPD (β 0.25, P < 0.001), extracellular water (ECW)/total body water (TBW) ratio (β 0.21, P < 0.001), skeletal muscle mass index (β 0.21, P < 0.001), log N-terminal brain natriuretic peptide (NT-proBNP) (β 0.17, P = 0.001), faster PET transport (β 0.15, P = 0.005), and normalized nitrogen appearance rate (β 0.13, P = 0.008). In addition to the longer dwell times of CAPD, greater peritoneal creatinine clearance and faster PET transporter status, we observed an association between increased PPCl and ECW expansion, increased NT-proBNP, estimated dietary protein intake and muscle mass, suggesting a link to sodium intake and sodium balance, increasing both ECW and conduit artery hydrostatic pressure resulting in greater vascular protein permeability. This latter association may explain reports linking PPCl to patient mortality.