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

Objective: To evaluate protein and caloric intake in peritoneal dialysis (P D) patients on an incremental dialysis schedule, in an attempt to discrimin ate the influence of residual renal function (RRF) on these nutritional par ameters. Design: Prospective observational study. Patients: Nine patients who had significant RRF at the beginning of PD ther apy, which permitted a schedule of incremental PD (i.e., the number of peri toneal exchanges was increased as the RRF fell) in order to maintain the su m of renal and peritoneal clearance (weekly Kt/V urea) at approximately 2. Methods: The mean adequacy parameters (urine and peritoneal Kt/V urea and c reatinine clearance) along with the mean dietary energy (DEI) and protein i ntake (DPI) estimated by 3-day diet histories, were determined 6 and 9 mont hs 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 pe riods were compared. The best determinants for the changes in DEI and DPI a fter 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 m(2) vs 56.78 +/- 11.77 L/week/1.73 m(2), p = 0.0001). Absolute and normalized DPI values for actu al body weight decreased after the loss of RRF (68.21 +/- 11.87 g/kg vs 59. 27 +/- 13.66 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 upta ke increased significantly after the loss of RRF, the mean total energy int ake (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 mea n total energy intake normalized for actual body weight decreased significa ntly 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 corre lated 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). Howe ver, 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 tim e on PD. Conclusions: The loss of RRF led to a reduction in dietary caloric and prot ein intake. The magnitude of the reduction in the DPI was strongly correlat ed with the increase in the energy delivered by peritoneal glucose uptake a nd with the decrease in the urinary Kt/V urea, but not with the total Kt/V urea.