OBJECTIVES:We evaluated the validity and reliability of ultrasonography measurement of rectus femoris cross-sectional area compared to computed tomography in patients in pre-dialysis chronic kidney disease and analyzed the association between these measurements and the diagnosis of sarcopenia.METHODS:One hundred patients with nondialysis chronic kidney disease were evaluated. Sarcopenia was defined using the criteria of the Foundation for the National Institutes of Health Sarcopenia Project (FNIH). The rectus femoris cross-sectional area was evaluated using ultrasonography and computed tomography.RESULTS:The prevalence of sarcopenia was 29% according to the FNIH criteria. The difference in mean rectus femoris cross-sectional area by ultrasonography and computed tomography was 3.97 mm, with a strong correlation between the two methods (p<0.001). Bland-Altman plot analysis showed good agreement between computed tomography and ultrasonography. Rectus femoris cross-sectional area was significantly correlated with muscle strength (r=0.300, p=0.002), lean body mass in the upper limbs (r=0.286, p=0.004), and lean body mass in the lower limbs (r=0.271, p=0.006). The prevalence of sarcopenia was 12% (n=12) based on the definition of low muscle mass according to ultrasonography of the rectus femoris cross-sectional area.CONCLUSION:Ultrasonography was demonstrated to be a valid and reliable method for evaluating the rectus femoris cross-sectional area in patients in pre-dialysis chronic kidney disease.