Peritoneal urea and creatinine clearances in continuous peritoneal dialysis patients with different types of peritoneal solute transport

Peritoneal clearances in peritoneal dialysis patients with different peritoneal transport types. We studied whether anuric subjects on continuous ambulatory peritoneal dialysis (CAPD) who achieve the target Kt/V urea of 2.0 weekly will also achieve the target normalized creatinine clearance (NCCr) of 60 liter/1.73m2 weekly, and the reasons of discrepancy between the two clearances in anuric subjects, by analyzing 476 clearance studies performed in 309 CAPD patients within 12 months of the performance of a peritoneal equilibration test (PET). On the basis of the PET, peritoneal solute transport was classified as low (37 clearance studies), low-average (199 studies), high-average (186 studies) and high (54 studies). We found that weekly values of Kt/V urea in the low transport group (LTG) was 1.74 ± 0.51, in the low-average transport group (LATG) was 1.66 ± 0.41, in the high-average transport group (HATG) 1.68 ± 0.41, and in the high transport group (HTG) 1.73 ± 0.46 (NS, variance analysis). Weekly values for NCCr, liter/1.73m2 were: LTG, 37.8 ± 9.0; LATG, 44.0 ± 9.2; HATG, 49.2 ± 10.0; HTG 56.8 ± 13.3 (P < 0.0001). The ratios of raw (not-normalized) peritoneal creatinine clearance to peritoneal urea clearance were: LTG, 0.65 ± 0.14; LATG, 0.76 ± 0.09; HATG, 0.84 ± 0.09; HTG, 0.91 ± 0.12 (P < 0.0001). Linear regression with Kt/V urea as x and NCCr as y revealed the following results: LTG, y=19.486 + 10.500x, r = 0.591 [if x = 2.0, y = 40.5, 95% confidence interval (95% CI) of y 25.3 to 55.7]; LATG, y=15.004 + 17.482x, r = 0.774 (if x = 2.0, y=50.0, 95% CI of y 38.4 to 61.6); HATG, y=15.285 + 20.162x, r = 0.829 (if x = 2.0, y = 55.6, 95% CI of y 44.4 to 66.8); HTG, y=14.945 + 24.134x, r = 0.839 (if x = 2.0, y = 63.2, 95% CI of y 48.4 to 78.1). Peritoneal solute transport type has a major effect on peritoneal creatinine clearance, but an insignificant effect on peritoneal urea clearance. Consequently, the majority of anuric patients who achieve a weekly Kt/V urea of 2.0 will have a weekly NCCr lower than 60 liter/1.73m2 and will require a Kt/V urea much higher than 2.0 to achieve the target NCCr of 60 liter/1.73m2 weekly. The current targets of urea and creatinine clearance are not compatible in anuric patients on CAPD