Influence of residual renal function on dietary protein and caloric intake in patients on incremental peritoneal dialysis

Abstract

Objective: To evaluate protein and caloric intake in peritoneal dialysis (PD) patients on an incremental dialysis schedule, in an attempt to discriminate the influence of residual renal function (RRF) on these nutritional parameters. Design: Prospective observational study. Patients: Nine patients who had significant RRF at the beginning of PD therapy, which permitted a schedule of incremental PD (i.e., the number of peritoneal exchanges was increased as the RRF fell) in order to maintain the sum of renal and peritoneal clearance (weekly Kt/V urea) at approximately 2. Methods: The mean adequacy parameters (urine and peritoneal Kt/V urea and creatinine clearance) along with the mean dietary energy (DEI) and protein intake (DPI) estimated by 3-day diet histories, were determined 6 and 9 months after the beginning of PD, when patients had RRF (period 1), and 6 and 9 months after the loss of RRF (period 2). The mean data obtained in both periods were compared. The best determinants for the changes in DEI and DPI after the loss of RRF were also investigated. Results: Mean total Kt/V urea was very similar in both periods (2.16 ± 0.32 vs 2.15 ± 0.18), although creatinine clearance decreased significantly after the loss of RRF (74.41 ± 12.28 L/week/1.73 m2 vs 56.78 ± 11.77 L/week/1.73 m2, p = 0.0001). Absolute and normalized DPI values for actual body weight decreased after the loss of RRF (68.21 ± 11.87 g/kg vs 59.27 ± 13.56 g/kg, p = 0.02; and 1.17 ± 0.32 g/kg/day vs 0.97 ± 0.32 g/kg/day, p = 0.01). Although the energy delivered by peritoneal glucose uptake increased significantly after the loss of RRF, the mean total energy intake (DEI plus peritoneal glucose uptake) was very similar in both periods (2141 ± 339 kcal/day vs 2010 ± 303 kcal/day, p = 0.13). However, the mean total energy intake normalized for actual body weight decreased significantly after the loss of RRF (37.5 ± 10.1 kcal/kg/day vs 32.8 ± 8.9 kcal/kg/day, p = 0.02). The changes in DEI and DPI between periods 1 and 2 correlated negatively with the difference of the energy delivered by peritoneal glucose uptake (r = 0.65, p = 0.05, and r = 0.88, p = 0.001, respectively). The magnitude of DPI changes between both periods correlated significantly with the magnitude of urinary Kt/V urea changes (r = 0.77, p = 0.01). However, there was no correlation between the changes in DPI and the changes in total Kt/V urea, total or renal creatinine clearance, or the length of time on PD. Conclusions: The loss of RRF led to a reduction in dietary caloric and protein intake. The magnitude of the reduction in the DPI was strongly correlated with the increase in the energy delivered by peritoneal glucose uptake and with the decrease in the urinary Kt/V urea, but not with the total Kt/V urea.