Mass balance: a quantitative guide to clinical nutritional therapy. I. The predialysis patient with renal disease.

Mass balance principles can be readily applied to the patient with chronic renal failure for the more structured management of his/her nutritional and clinical course. Urine values provide valuable information with respect to rates of protein catabolism and sodium intake; creatinine excretion rates provide a ready check on data accuracy and lean body mass; urea and creatinine clearance can be calculated, if blood levels of these solutes are known. With accurate data on creatinine generation and the ratio of urea to creatinine clearance, creatinine clearance, urea generation, and protein catabolism rates can be estimated from blood levels alone. These techniques then provide quantitative guidance for the nutritional/medical staff in its efforts to control the clinical course of the patient with severly diminished renal function.