Dissociation between the correlation of peritoneal and urine Kt/V with sodium and fluid removal: a possible explanation of their difference on patient survival.

BACKGROUND

It has been shown that residual renal function but not peritoneal clearance predicted patients' survival in peritoneal dialysis therapy. In the present study, we tried to explore the potential causes resulting in the difference between residual renal function and peritoneal dialysis in continuous ambulatory peritoneal dialysis (CAPD) patients.

METHODS

A cross sectional study was performed during July and August 2003 to evaluate the dialysis adequacy in CAPD patients who were clinically stable and had daily urinary volume more than 100 ml.

RESULTS

A total of 45 patients (male 27 and female 18) with an average ( +/- SD) age of 61.76 +/- 13.27 years were included in this study. The daily urinary volume and dialysate ultrafiltration volume were 570.33 +/- 395.47 ml and 726.09 +/- 454.01 ml, respectively. Peritoneal urea clearance (Kt/V) correlated significantly with the drained daily dialysate volume (r = 0.362, P < 0.01), but not with peritoneal net fluid removal (ultrafiltration) (r = 0.232, P > 0.05) and sodium removal (r = 0.139, P > 0.05). On the other hand, there were strong positive correlations between residual renal Kt/V and daily urine volume (r = 0.802, P < 0.001), as well as between residual renal Kt/V and urinary sodium removal (r = 0.670, P < 0.001).

CONCLUSIONS

High residual renal Kt/Vurea represents both higher solute clearance and higher sodium and fluid removal, but higher peritoneal Kt/Vurea is not necessarily associated with better sodium and fluid removal. This dissociation might explain the differences on the survival of patients and peritoneal clearances.