Independent effects of residual renal function and dialysis adequacy on actual dietary protein, calorie, and other nutrient intake in patients on continuous ambulatory peritoneal dialysis

Previous studies have suggested that the cross-sectional relationship obser ved between total solute clearance (Kt/V) and dietary protein intake (DPI) in patients undergoing dialysis is possibly mathematical in origin. A cross -sectional study on 242 patients undergoing continuous ambulatory peritonea l dialysis (CAPD) was performed to determine the differential effects of di alysis adequacy and residual renal function (RRF) on actual dietary intake. All patients underwent a 7-d food frequency questionnaire to quantify dail y dietary protein, calorie (DCI), and other nutrient intake, subjective glo bal assessment (SGA), and collection of 24-h dialysate and urine for total (PD and renal) Kt/V and RRF. Patients were categorized into three groups: I (n = 94), total Kt/V greater than or equal to1.7 and GFR >0.5 ml/min per 1 .73 m(2); II (n = 58), total Kt/V = greater than or equal to1.7 but GFR <0. 5 ml/min per 1.73 m(2); and III (n = 90), total Kt/V <1.7. Sixty-nine perce nt versus 62% versus 42% of group I versus II versus III patients were well nourished according to SGA (P = 0.004). DPI (1.23 [0.47] versus 1.12 [0.49 ] versus 0.99 [0.40] g/kg per d; P = 0.002) and DCI (27.3 [8.9] versus 23.8 [8.6] versus 23.0 [8.2] kcal/kg per d; P = 0.002) showed significant decli ne across the three groups. Intake of other nutrients, including carbohydra te, fat, ratty acids, and cholesterol was higher for group I compared with groups II and III. Adjusting for age, gender, weight, and diabetes, every 1 ml/min per 1.73 m(2) increase in GFR was associated with a 0.838-fold incr ease in DCI (95% confidence interval to interval, 0.279 to 1.397, P = 0.003 ) and a 0.041-fold increase in DPI (95% confidence interval, 0.009 to 0.072 ; P = 0.012), whereas every 0.25-unit increase in total (PD and renal) Kt/V was associated with a 0.570-fold increase in DCI (95% confidence interval, 0.049 to 1.092; P = 0.032) and a 0.052-fold increase in DPI (95% confidenc e interval, 0.023 to 0.081; P = 0.001). Greater small-solute clearances are associated with better dietary intake and better nutrition. The study conf irmed significant and independent effect of RRF but not PD solute clearance , on actual DPI, DCI, and other nutrient intake in patients on CAPD.