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

We analyzed the effect of diabetes on the decline of residual renal functio n during the course of CAPD in a cross-sectional study including 105 diabet ic subjects (41 women) who had 207 clearance studies and 125 non-diabetic s ubjects (50 women, 265 clearance studies). CAPD duration was 11.5+/-10.5 mo nths 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, N DG 0.53+/-0.49) and C-cr (DG 31.0+/-28.7 NDG 29.3+/-26.5 L/1.73 m(2)) did n ot differ. The slopes of the regressions of CAPD duration on renal clearanc es did not differ. These regressions allowed estimates of the time, from th e onset of CAPD, at which renal clearances become negligible. These estimat es differed for both urea clearance (DG 35.3, NDG 50.5 months) and creatini ne clearance (DG 43.2, NDG 57.6 months). The slope of the regression of ren al urea clearance on renal creatinine clearance was steeper in the DG, sugg esting a higher renal creatinine clearance in the DG than in the NDG when r enal urea clearance is the same in the two groups. Subtle differences in th e rate of decline of renal function can be detected between diabetic and no n-diabetic subjects on CAPD by detailed statistical analysis. These finding s are supportive of the studies which have identified diabetes mellitus as a predictor of loss of residual renal function during the course of CAPD. I n addition, the relationship between the renal urea and creatinine clearanc es differs between diabetic and non-diabetic subjects on CAPD. Therefore, t he dose of CAPD required for adequate total clearances may differ between d iabetic and non-diabetic subjects.