RELATIONSHIP BETWEEN UREA CLEARANCE AND P ROTEIN CATABOLIC RATE - IMPORTANCE OF THE RESIDUAL RENAL-FUNCTION

The significance of Kt/V urea and normalized protein catabolic rate (P CR) as markers of dialysis adequacy and nutritional status, respective ly, are controversial. Perhaps normalization for urea distribution vol ume and actual body weight may lead to misinterpretations of these par ameters. Moreover, the quality of urea clearance (renal or peritoneal) may largely determine the relationship between Kt and PCR. In order t o investigate what factors may affect the relationship between Kt and PCR in uremic patients, 94 samples from 37 patients with end-stage ren al failure prior to starting dialysis treatment (group A), 50 samples from 22 patients on CAPD with residual renal function (urinary Ccr > 5 L/weekly/1.13 m(2)) (group B) and 94 samples from 28 patients on CAPD with no residual renal function (group C), were studied. Each study w as carried out at 3-month intervals and included: Kt/V urea, PCR, diet ary protein intake (diet survey), Ccr, and a nutritional score calcula ted from anthropometric and biochemical measurements (lymphocyte count , transferrin, serum albumin, and lean body mass estimated by total cr eatinine production). PCR and urea clearance (Kt) correlated with nutr itional scores in CAPD patients. However, Kt/V did not correlate with nutritional scores. The mean nutritional score in group C was signific antly worse than in groups A and B. PCR significantly correlated with Kt in all 3 groups (group A: r = 0.65; B: r = 0.55; C: r = 0.63, p < 0 .0001). The slope of the regression equation in group C was steeper th an in groups A and B (0.65, 0.60, 0.85 respectively), but the intercep ts of the regression equation from groups A and B were higher than gro up C (35.1 vs 23.2 vs 2.7, respectively). According to these equations , at any given Kt value in the medium and low range, the PCR was alway s higher in the groups with residual renal function than the group wit h anuric. These results suggest that residual renal function may play an important role in protein intake of patients on CAPD. Target Kt/V u rea in these patients should be adapted to this observation.