Lean body mass estimation by creatinine kinetics

A new technique for estimating lean body mass (LBM) from creatinine kinetics has been developed. It is based on the principle that creatinine production is proportional to LBM and that, in the steady state, creatinine production is equal to the sum of creatinine excretion (urinary and dialytic) and metabolic degradation. This technique was applied to 17 normal subjects, 26 stable, chronic hemodialysis (HD) patients, and 71 stable, chronic peritoneal dialysis (PD) patients. In the HD group, LBM was also determined by bioimpedance in 11 patients and calculated from total body water, measured as the volume of urea distribution of a sterile urea infusion, in 15 patients. In normal subjects and in the PD group, LBM was assessed by creatinine kinetics as well as by bioimpedance, near infrared, and anthropometric techniques. In the HD patients, LBM by creatinine kinetics correlated significantly with LBM from total body water and the bioimpedance technique. There was no statistical difference between the total body water and creatinine kinetics techniques, but the bioimpedance values were systematically higher than those obtained by the kinetic technique. In the PD group and in normal volunteers, LBM values by creatinine kinetics correlated significantly with the other methods but were lower. Forty-seven percent of the HD patients and 66% of the PD patients had significantly lower LBM by creatinine kinetics than expected for their sex and age. Estimation of LBM by creatinine kinetics is proposed as a simple and convenient technique for the routine nutritional assessment of dialysis patients.