The Effect of Declining Small Solute Clearance on Protein Intake and Nutritional Status in Progressive Renal Failure

Kim, Jin Kook; Lee, Eun Ah; Youn, Dong Jin; Chung, Sung Hee; Na, Myung Hee; Han, Dong Chul; Park, Min Sun; Hwang, Seung Duk; Lee, Hi Bahl

Abstract

BACKGROUNDS: Malnutrition is common in patients with chronic renal failure(CRF) and various signs of malnutrition are strong predictors of increased morbidity and mortality. Monitoring of protein intake and nutritional status is therefore important in the clinical management of CRF patients. Few studies have demonstrated direct correlations among renal function, protein intake, and nutritional status in a prospective study although clinical experiences suggest such relationship. The aim of this study was to prospectively evaluate correlations between renal function, protein intake, and nutritional status during progressive renal failure.
METHODS
A total of 431 studies on renal function, protein intake, and nutritional status was carried out in 282 patients with normal renal function and varying degrees of renal failure before beginning dialysis. Renal functional indices included weekly Kt/Vurea, total weekly creatinine clearance(Ccr, L/week/1.73m2), creatinine clearance(Ccr, mL/min/1.73m2), urea clearance(Curea, mL/min) and residual renal function(RRF, mL/min). Protein intake was assessed from the protein equivalent of total nitrogen appearance normalized by standard weight(nPNA, g/kg/day) by DOQI formula[nPNA(D)], Bergstr m formula 1[nPNA(B1)] and Bergstr m formula 2[nPNA(B2)]. Nutritional indices were fat free edema free body mass(FFEFBM, kg) by creatinine kinetics, %lean body mass(LBM, %) and serum albumin(g/dL). We evaluated correlations between renal function, protein intake and nutritional status by linear regression analysis. In a separate analysis, 237 studies from 94 patients with follow-up studies were analyzed for correlations among renal function, protein intake, and nutritional status.
RESULTS
There was a highly significant correlation among weekly Kt/Vurea, weekly creatinine clearance, and residual renal function, among nPNA(D), nPNA (B1), nPNA(B2), and between FFEFBM and %LBM. Significant correlation was also observed between weekly Kt/Vurea and nPNA, between weekly Kt/ Vurea and FFEFBM, between weekly Kt/Vurea and %LBM, between nPNA and FFEFBM, and between nPNA and %LBM. The results were the same in patients with follow-up studies.
CONCLUSION
These results clearly demonstrate that renal urea and creatinine clearance is closely correlated with protein intake and nutritional status in predialysis patients. With declining small solute clearances, protein intake decreased and nutritional status became worse. Starting dialysis before malnutrition becomes apparent may improve patient morbidity and mortality after dialysis.