The relationship between Kt/V-urea and nPNA in anuric peritoneal dialysis patients: A comparison with predialysis patients

Objective: It is unknown whether a given level of urea clearance by the nat ive kidneys provides better or similar control of uremia than the same leve l of urea clearance by continuous peritoneal dialysis (PD). More insight in to possible differences between renal and peritoneal urea clearances is war ranted. Therefore, we investigated the relationship between Kt/V-urea and p rotein equivalent of total nitrogen appearance normalized to body weight (n PNA), the relationship between urea clearance and creatinine appearance, an d other nutritional parameters in PD patients without residual renal functi on, and in predialysis end-stage renal disease patients. Patients: All patients participated in the Netherlands Cooperative Study on the Adequacy of Dialysis. This is a prospective cohort study of incident d ialysis patients, in whom regular assessments of renal function are done. A group of 75 PD patients was identified at the first followup assessment in which their urine production was less than 100 mL/day. These patients were considered the anuric group. This group was compared with a control group of 97 predialysis patients studied 0-4 weeks before the start of dialysis t reatment. Results: Linear relationships were present between Kt/V-urea and nPNA, in b oth the predialysis patients and the anuric PD patients. A significant diff erence was present between the slopes of the two regression lines (0.40 vs 0.18, p=0.007). When Kt/V-urea, exceeded 1.3/week, a given level of Kt/V-ur ea was associated with a higher nPNA in predialysis than in anuric PD patie nts. Similar relationships were found between Kt(urea) and PNA. Kt(urea) wa s also significantly related to urine or dialysate creatinine appearance. A significant difference existed between the slopes of the regression lines in the two groups of patients (p<0.001). A weekly Kt(urea) of 70 L was asso ciated with a urine creatinine appearance of 11.0 mmol/day and a dialysate creatinine appearance of 8.4 mmol/day. Nutritional status measured with cre atinine appearance and Subjective Global Assessment was better in the predi alysis population, despite much lower values for Kt/V-urea in these patient s. Conclusions: The relationship between Kt/V-urea,, and nPNA in anuric PD pat ients is different from that in a predialysis population. It follows from o ur results that, when Kt/V-urea, is above 1.3/week, a given level of Kt/V-u rea is associated with a higher nPNA in predialysis than in anuric PD patie nts. This challenges the concept of equivalency between renal and peritonea l Kt/V-urea with respect to control of uremic morbidity.