Calf Knows Best: Gastrocnemius Sonoelastography as a Sensitive Marker of Muscle Mass in End-Stage Kidney Disease

Background : Muscle loss and weakness are hallmarks of end-stage kidney disease (ESKD), driving disability and poor outcomes. Traditional assessments of muscle health are often invasive, time-consuming, or insensitive. Sonoelastography, which quantifies muscle stiffness, offers a noninvasive alternative. Yet, the optimal muscle group for detecting sarcopenia in ESKD remains unclear. Methods : In this prospective cohort study, 150 ESKD patients (mean age 64.7 ± 13.5 years; BMI 23.9 ± 4.3 kg/m²) underwent sonoelastography of five muscle groups: biceps, supinator, erector spinae, quadriceps, and gastrocnemius. Each site was measured three times over 3-month intervals. Muscle mass was evaluated using dual-energy X-ray absorptiometry (DXA) as appendicular lean mass/height² (ALM/H²). Correlations between Hard (%) values and ALM/H² were examined with Pearson's correlation and multivariable regression models. Results : Among all examined muscles, gastrocnemius Hard (%) emerged as the most robust correlate of ALM/H² (r = 0.471, p < 0.001), outperforming upper- and trunk-limb muscles. Regression analysis confirmed gastrocnemius stiffness as an independent predictor of muscle mass (ß = 0.497, p = 0.001), even after adjusting for demographic and clinical confounders. Conclusion : The calf muscle, often overlooked in routine assessments, outperformed other muscle groups as the most sensitive sonoelastographic marker of muscle mass in ESKD. This finding highlights the gastrocnemius as a practical"sentinel muscle" for noninvasive monitoring of sarcopenia in dialysis populations.