Standardized thigh muscle area measured by computed axial tomography as an alternate muscle mass index for nutritional assessment of hemodialysis patients

BACKGROUND: Quantification of muscle mass, which represents the largest protein pool in the body, is important for nutritional assessment but is difficult to achieve with conventional methods in hemodialysis patients. OBJECTIVE: We measured the cross-sectional area of the thigh occupied by muscle by using computed tomography and compared this with other muscle mass indicators. DESIGN: Thigh muscle area (TMA) was examined and correlated with creatinine production and various nutritional indexes in 163 patients undergoing hemodialysis. Where appropriate, TMA was expressed relative to bone area in the thigh (TBA) to avoid the influence of body size. RESULTS: TMA was highly correlated with creatinine production as measured in the spent dialysate (r = 0.85, P < 0.001), indicating that TMA substantially reflects total-body muscle mass. TMA standardized for TBA was negatively correlated with age and positively correlated with other nutritional indicators including body weight, body mass index, serum albumin, serum transthyretin, and protein catabolic rate. Multiple regression analysis revealed that of these variables, age, serum albumin, and protein catabolic rate independently predicted TMA standardized for TBA. By using correlations with various nutritional indicators, we concluded that patients with a value <10.0 for TMA standardized for TBA were likely to be malnourished whereas those with a value >13.0 were likely to be well nourished. CONCLUSIONS: These results indicate that TMA standardized for TBA, measured by computed tomography, is a reliable indicator of muscle mass that could be used for nutritional assessment of hemodialysis patients.