Independent effects of residual renal function and dialysis adequacy on nutritional status and patient outcome in continuous ambulatory peritoneal dialysis

Dialysis adequacy has a major impact on outcome of continuous ambulatory pe ritoneal dialysis (CAPD) patients. However, there is a substantial confound ing effect by residual renal function in most studies, We differentiated th e effects of dialysis adequacy from those of residual renal function on nut ritional status and outcome of CAPD patients. We identified 168 CAPD patien ts treated in our center between September 1995 and December 1996 and categ orized them into three groups: 49 patients with an average total Kt/V of 1. 93 +/- 0.18 and a median residual glomerular filtration rate (GFR) of 0.07 mL/min/1.73m(2) in the dialysis-dependent (DD) group; 48 patients with an a verage total Kt/V of 2.03 +/- 0.25 and a residual GFR of 2.33 mL/min/1.73m( 2) in the residual renal function (RRF) group; and 71 patients with an aver age total Kt/V of 1.38 +/- 0.22 and a residual GFR of 0.05 mL/min/1.73m(2) in the control (CTL) group. They were followed-up for 1 year to compare bas eline nutritional status and I-year morbidity, Baseline normalized protein catabolic rates (NPCR) are 1.00 +/- 0.20 and 0.96 +/- 0.19 (for RRF and DD, respectively) versus 0.89 +/- 0.16 g/kg/d for CTL (P < 0.01). Percentage l ean body mass (%LBM) was 71.6 +/- 9.8 and 71.5 +/- 10.0 (for RRF and DD, re spectively) versus 65.2 +/- 8.5% for CTL (P < 0.001). No difference was see n in the nutritional status between RRF and DD groups, Duration of hospital ization for 1 year was 6.9 +/- 11.8 days in the RRF group versus 14.9 +/- 2 5.1 in the DD and 10.6 +/- 11.6 days in the CTL groups (P < 0.05). The peri tonitis rate was 44.4 patient-months for the RRF group, versus 13.6 for the DD and 12.9 for the CTL groups (P < 0.05), There also was a trend toward s uperior I-year technique survival in the RRF group, but the number of obser vations was small. There was no difference in duration of hospitalization, peritonitis rate, and technique survival between the DD and CTL groups. Sho rt-term morbidity in patients without residual renal function appears to be independent of total Kt/V, although Kt/V may have some effects on nutritio nal status. The assumption that renal and peritoneal clearances are equival ent must be carefully reexamined. Further studies on the effect of dialysis adequacy in patients without residual renal function are urgently needed. (C) 1999 by the National Kidney Foundation, Inc.