Quadriceps muscle behavior assessed by ultrasound in septic patients: A systematic review

Sepsis induces accelerated catabolism of skeletal muscle, but the extent and clinical relevance of quadriceps atrophy remain unclear. This systematic review investigated studies that applied bedside ultrasound (US) to measure the quadriceps in adults (≥18 years) with sepsis or septic shock admitted to intensive care units (ICUs). Four databases were searched through June 8, 2025, and six prospective cohorts (234 patients) met the PEOS criteria. All studies reported a reduction in muscle mass or thickness during hospitalization, with assessments conducted between 48 h after ICU admission and up to 14 days. The magnitude of muscle loss varied considerably across studies, with median reductions in rectus femoris and quadriceps thickness ranging from 10% to 30%. Greater muscle loss was associated with important clinical outcomes, such as longer ICU stays, prolonged mechanical ventilation, and reduced muscle strength after discharge. These findings suggest that quadriceps loss, as measured by ultrasound, may serve as a prognostic indicator of these clinical outcomes. Heterogeneity in cutoff points, measurement timing, and metrics prevented meta-analysis and highlighted methodological gaps, including small sample sizes and lack of standardized protocols. Nonetheless, the US proved to be a feasible, repeatable, and radiation-free tool for serial monitoring of muscle in sepsis. Multicenter studies using standardized measurement of rectus femoris cross-sectional area and robust clinical outcomes are needed to establish reference trajectories and guide nutritional or rehabilitation interventions aimed at mitigating catabolism and enhancing functional recovery.