Does Peritoneal Protein Transport Increase with Peritoneal Dialysis Therapy Duration and Lead to Extracellular Water Overload in Peritoneal Dialysis Patients?

Faster peritoneal transport status has been associated with adverse outcomes for peritoneal dialysis (PD) patients. Peritoneal protein clearance, through large pores, may be a surrogate marker of local inflammation. We wished to determine whether peritoneal protein transport increased with PD duration or was associated with extracellular water (ECW) expansion. We studied the relationships between 4 h Dialysate (D)/Serum (S) protein and ECW excess, using multifrequency bioelectrical impedance assessments, in 103 PD patients with up to 4 years of prospectively collected peritoneal equilibrium test (PET) results. 4 h PET D/S total protein and creatinine ratios were stable over time (K-W test, P = 0.063 and P = 0.3357, respectively). The initial PET 4 h D/S creatinine and D/S total protein correlated with ECW excess (r = 0.33, P = 0.003, and r = 0.27, P = 0.019, respectively), but thereafter there was no association. CRP and albumin did not correlate with 4 h D/S creatinine or total protein. Serial 4 h D/S total protein and 4 h D/S creatinine correlated all time points (P < 0.001). At the start of PD therapy, over-hydration (ECW excess) was observed with higher 4 h D/S creatinine and 4 h D/S total protein ratios, suggesting initial exposure to PD fluids causes faster transport. Thereafter changes in peritoneal creatinine and total protein transport mirrored each other suggesting that similar factors lead to changes in both small and large pore transport, and there was no sustained increase in larger pore transport with therapy time.