Renal clearances in continuous ambulatory peritoneal dialysis: differences between diabetic and non-diabetic subjects

We analyzed the effect of diabetes on the decline of residual renal function during the course of CAPD in a cross-sectional study including 105 diabetic subjects (41 women) who had 207 clearance studies and 125 non-diabetic subjects (50 women, 265 clearance studies). CAPD duration was 11.5+/-10.5 months in the diabetic group (DG) and 16.8+/-18.6 months in the non-diabetic group (NDG, P < 0.001). The DG had lower urine volume than the NDG (0.52+/-0.46 vs 0.61+/-0.50 L/24-h, P < 0.05), while urine-to-plasma concentration ratio was higher in the DG for creatinine (13.5+/-9.4 vs 11.5+/-11.0, P <0.05) and did not differ for urea. Weekly renal Kt/V urea (DG 0.51+/-0.57, NDG 0.53+/-0.49) and Ccr (DG 31.0+/-28.7 NDG 29.3+/-26.5 L/1.73 m2) did not differ. The slopes of the regressions of CAPD duration on renal clearances did not differ. These regressions allowed estimates of the time, from the onset of CAPD, at which renal clearances become negligible. These estimates differed for both urea clearance (DG 35.3, NDG 50.5 months) and creatinine clearance (DG 43.2, NDG 57.6 months). The slope of the regression of renal urea clearance on renal creatinine clearance was steeper in the DG, suggesting a higher renal creatinine clearance in the DG than in the NDG when renal urea clearance is the same in the two groups. Subtle differences in the rate of decline of renal function can be detected between diabetic and non-diabetic subjects on CAPD by detailed statistical analysis. These findings are supportive of the studies which have identified diabetes mellitus as a predictor of loss of residual renal function during the course of CAPD. In addition, the relationship between the renal urea and creatinine clearances differs between diabetic and nondiabetic subjects on CAPD. Therefore, the dose of CAPD required for adequate total clearances may differ between diabetic and non-diabetic subjects.