Ultrasonographic evaluation of quadriceps femoris muscle mass in critically ill patients aged 60 years and older: a prospective observational study

Background and aims Muscle wasting is a common complication in critically ill older adults admitted to intensive care units (ICU), with significant implications for morbidity and mortality. Ultrasound represents a promising bedside tool for assessing muscle mass changes. This study aimed to evaluate changes in quadriceps femoris muscle mass using ultrasonography at ICU admission and after 7 days of stay in patients aged 60 years and older. Methods A prospective cohort study with repeated measurements was conducted between December 2024 and May 2025. Patients aged ≥60 years admitted to the ICU were included. Ultrasonographic measurements included rectus femoris cross-sectional area (RFCSA), bilateral quadriceps muscle thickness, and rectus femoris pennation angle at admission and day 7. Clinical characteristics, severity scores (APACHE II, SOFA), and functional status (Barthel index) were recorded. Statistical analysis included Wilcoxon signed-rank test and robust statistics. Results Fifty patients were analyzed (60% male, median age 72.5 years). Significant muscle mass reductions were observed: RFCSA decreased by 16.2% (2.525–2.115 cm 2 , p < 0.001), right quadriceps thickness by 14.6% (2.012–1.719 cm, p < 0.001), left quadriceps thickness by 20.2% (2.049–1.635 cm, p < 0.001), and pennation angle by 18.2% (7.664°–6.270°, p < 0.001). ICU mortality was 30%. Multivariate analysis identified advanced age, female sex, hypoglycemic agent use, higher SOFA scores, and lower premorbid Barthel index as factors associated with greater muscle loss. Conclusion Critically ill older adults experience significant quadriceps muscle mass loss within the first week of ICU stay, as measured by bedside ultrasonography. These findings support the implementation of early muscle assessment and targeted interventions in this vulnerable population.