Dialysis adequacy, residual renal function and serum concentrations of selected low molecular weight proteins in patients undergoing continuous ambulatory peritoneal dialysis.

Background: Low molecular weight proteins (LMWP) are considered uremic toxins. There is controversy whether in peritoneal dialysis (PD) the elimination of these toxins is influenced mainly by dialysis or by residual renal function (RRF).

Material/methods: The aim of our study was to evaluate the relationship between serum levels of selected LMWPs, dialysis adequacy, and RRF in PD patients. 27 stable subjects were studied, mean age 50+/-11, dialyzed for a median period of 10 months. Serum activity of acid RNA-se and alkaline RNA-se was measured by spectrophotometry, and serum alpha1-microglobulin ((alpha) 1M) concentration by ELISA. Kt/V and weekly creatinine clearance (wClCr) were assessed as adequacy indices (both as the sum of renal and dialysis components) and RRF as the mean of residual urea and creatinine clearances.

Results: Significant inverse correlations were found between RRF and (alpha) 1M level, as well as alkaline RNA-se activity (p<0.0001). A similar relationship was found for residual Kt/V (p<0.0001 for (alpha) 1M and alkaline RNA-se). There was no significant correlation between acid RNA-se activity and any tested parameter of adequacy. When the cutoff points of wClCr = 60 L/week/m2, total Kt/V = 2.0, or RRF=2.0 ml/min were used, we found (alpha)1M level and alkaline RNA-se activity to be significantly lower in patients with higher values of the

Conclusions: RRF plays an important role in elimination of LMWP in PD. The activity of alkaline RNA-se and acid RNA-se behaves differently in these patients.