Lean body mass by Dual Energy X-ray Absorptiometry (DEXA) and by urine and dialysate creatinine recovery in CAPD and pre-dialysis patients compared to normal subjects.

The urinary creatinine excretion rate is a function of the muscle mass which, in normal subjects, is shown to be correlated with lean body mass. Dual Energy X-ray Absorptiometry (DEXA) has been shown to correlate well with other methods for the measurement of body composition. The purpose of the present study was to compare estimates of lean body mass (LBM) by DEXA scan with urine and dialysate creatinine recovery in uremic patients and in normal subjects. We included 63 normal subjects with a creatinine clearance of 60-120 mL/min, 30 uremic predialysis patients with creatinine clearance below 30 mL/min, and 20 continuous ambulatory peritoneal dialysis (CAPD) patients. LBM was measured by DEXA scan on the same day as urine collection and was estimated from creatinine recovery with and without correction for extrarenal creatinine clearance. Results from the normal subjects showed no difference in estimates of LBM by the different methods but, in predialysis and CAPD patients, a significant difference between methods of estimating LBM was found, even when correction for extrarenal clearance in uremic patients was performed. In normal subjects: DEXA 43.6 kg versus creatinine excretion 43.2 kg (NS). In predialysis patients: DEXA 47.8 kg versus 37.6 kg (p < 0.001) corrected 44.8 kg (p < 0.05). In CAPD patients: DEXA 47.2 kg versus 32 kg (p < 0.001) corrected 42.6 kg (p < 0.05). In conclusion, the urine and dialysate creatinine excretion is an inaccurate estimate of LBM, but reflects the muscle mass and, in that respect, is an important tool in the nutritional evaluation of uremic patients.(ABSTRACT TRUNCATED AT 250 WORDS)