Rectus femoris ultrasound identifies sarcopenia and predicts poor outcomes in patients with acute decompensation of cirrhosis.

Background & Aims: Sarcopenia is common and associated with poor outcomes in decompensated cirrhosis. While computed tomography (CT) scan, with measurement of skeletal muscle index (SMI) at L3, is the gold standard for assessing sarcopenia in patients with cirrhosis, it is costly, exposes patients to radiation, and requires specialized software. This study evaluated the accuracy of bedside ultrasound measurement of the rectus femoris cross-sectional area (RF-CSA) in assessing sarcopenia and its prognostic value in patients with cirrhosis. Methods: A prospective two-phase study was conducted. Phase 1 analyzed correlations between RF-CSA and SMI, as well as other sarcopenia predictors, in 77 patients. In phase 2, RF-CSA was measured at the bedside in 203 patients with acute decompensation of cirrhosis, followed up until death, liver transplant, or 90 days. Interoperator reliability was assessed in 38 patients using the intraclass correlation coefficient (ICC). Results: RF-CSA strongly correlated with SMI (r = 0.748, p <0.001), outperforming muscle thickness and anthropometric parameters. RF-CSA was an independent predictor of sarcopenia (hazard ratio (HR) = 0.27, p <0.001) and demonstrated high discrimination ability for sarcopenia (AUROC = 0.90 in men and 0.92 in women). Lower RF-CSA was independently associated with an increased risk of developing sepsis, acute kidney injury, shock, and overt hepatic encephalopathy. RF-CSA was an independent predictor of 90-day mortality (subdistribution HR = 0.57, p = 0.006). Intra- and interoperator reliability were high (ICC = 0.980 and 0.947, respectively, p <0.001 for both). Conclusions: RF-CSA assessment by thigh ultrasound is an accurate, reliable, and easy point-of-care tool for assessing sarcopenia in patients with decompensated cirrhosis. It is also associated with the risk of complications and mortality. Impact and implications: Sarcopenia is strongly associated with adverse clinical outcomes in patients with cirrhosis. However, its assessment remains infrequent in clinical practice because of the reliance on CT-based SMI measurements, which are costly, expose patients to radiation, and require specialized software. This study demonstrates that bedside ultrasound measurement of RF-CSA is a simple, accurate, and reliable alternative for assessing sarcopenia in patients with decompensated cirrhosis. RF-CSA not only correlates well with SMI, but also independently predicts sarcopenia, complications, and 90-day mortality. Its strong prognostic value underscores its potential for routine use in clinical practice. Moreover, RF-CSA assessment is easy to learn, highly reproducible across different operators, and feasible for point-of-care application. These findings support the integration of ultrasound-based muscle assessment into routine cirrhosis management, enabling early risk stratification and potentially guiding targeted interventions to improve patient outcomes.