Surgical-related muscle loss (SRML) is a common postoperative complication, defined as a reduction of at least 10% in preoperative skeletal muscle mass in at least one upper limb and one lower limb by postoperative day 7. Patients undergoing gastric cancer surgery are typically older and at high risk for low muscle mass, and surgical stress further exacerbates the incidence of SRML. In addition to limb skeletal muscles, swallowing-related muscle groups may also be affected, leading to impaired nutritional intake and increased risks of postoperative complications and mortality. In recent years, ultrasonography-owing to its noninvasiveness, bedside feasibility, and repeatability-has been regarded as a practical tool for monitoring postoperative muscle changes. This study aims to longitudinally track changes in skeletal muscle thickness using ultrasound in patients undergoing gastrectomy for gastric cancer, while concurrently assessing nutritional status and clinical recovery, with the goal of establishing an early clinical assessment model for detecting postoperative muscle loss to inform nutritional interventions and postoperative care. Accordingly, this project will conduct a cohort study of 100 patients to investigate postoperative muscle loss and associated risk factors, including swallowing function and postoperative complications. This prospective observational study will enroll patients aged ≥20 years who undergo gastrectomy and provide written informed consent; individuals with psychiatric conditions that may impair consent or study procedures will be excluded. A total of 100 patients undergoing gastric cancer resection will be assessed preoperatively (T0) and at postoperative day 7 ±2 (T1), 1 month ±1 week (T2), 3 months ±2 weeks (T3), 6 months ±2 weeks (T4), and 12 months ±2 weeks (T5). Assessments will include ultrasound-measured muscle thickness, bioelectrical impedance analysis, handgrip strength and limb muscle strength, tongue pressure, life quality and activity associated questionnaire, and blood tests for nutritional, markers. The expected outcome is that patients with lower preoperative muscle mass and those at high risk of malnutrition will be more susceptible to postoperative muscle loss, and the occurrence of postoperative muscle loss will be associated with an increased risk of postoperative complications.
