Evaluation of Changes in the Quadriceps Femoris Muscle in Critically Ill Children Using Ultrasound Compared with Controls

BACKGROUND: Critically ill children in the pediatric intensive care unit (PICU) are exposed to immobilization, mechanical ventilation, and systemic inflammation, which can lead to early skeletal muscle wasting. Ultrasound assessment of the quadriceps femoris provides a feasible bedside method to detect muscle changes during critical illness. AIM: To evaluate changes in quadriceps femoris muscle thickness and echogenicity in critically ill children using ultrasound and compare them with age-matched healthy controls. MATERIALS AND METHODS: This prospective observational study (January 2024-June 2025) included 348 children: 174 critically ill mechanically ventilated PICU patients and 174 age-matched controls. Quadriceps muscle thickness and echogenicity were assessed using standardized ultrasound measurements. Cases were evaluated on day 1, day 3, and day 5, while controls were assessed once. RESULTS: Baseline muscle thickness was similar in cases and controls (1.60 cm). In cases, mean thickness declined to 1.54 cm by day 3 ( P = 0.031) and 1.48 cm by day 5 ( P < 0.001), representing a 7.5% reduction, while controls showed no significant change. Thickness reduction occurred in 59.2% of cases versus none of the controls ( P < 0.001). Increased muscle echogenicity was observed in 16.7% of cases and in no controls ( P < 0.001). Muscle changes showed no significant association with age or sex. CONCLUSION: Ultrasound detected early reductions in quadriceps muscle thickness and increased echogenicity in critically ill children. Serial bedside muscle ultrasound may be useful for monitoring early muscle changes in pediatric critical care.