Abstract: Objective To investigate the relationship between skeletal muscle index of the third lumbar vertebrae (L3-SMI) and clinical indexes in patients with acute on chronic liver failure (ACLF). Methods 126 patients with ACLF were admitted to our hospital From January 2015 to June 2019,and underwent abdominal CT or MRI scan. L3-SMI was calculated and the clinical characteristics of patients with different SMI levels were compared. Results In this study, 113 male patients and 13 female patients were included; the L3-SMI of male patients was (40.3±7.4) cm²/m², significantly higher than that of female patients [(33.9±4.5) cm²/m², P< 0.05]; the L3-SMI of male patients with liver cirrhosis was (38.1 ±5.9)cm²/m², which was significantly lower than that of non-liver cirrhosis patients [(42.0±7.9)cm²/m², P＜0.05]; the L3-SMI of patients with alcoholic liver disease was (34.8±6.8)cm²/m², which was significantly lower than that of patients with non-alcoholic liver disease [(41.5±7.0)cm²/m², P＜0.05]; the L3-SMI in 90-day survival was (40.7±7.7) cm²/m², not significantly different compared to [(38.8±6.3) cm²/m², P > 0.05]in dead patients; according to the median L3-SMI, the male patients were divided into low L3-SMI group (n = 61) and high L3-SMI group (n = 52); the percentages of hepatic encephalopathy in low L3-SMI group and high L3-SMI group were 19.7% and 13.5%, respectively (P > 0.05), the 90-day survival rate in low L3-SMI group was 68.9%, not significantly different compared to 76.9% in high L3-SMI group (P> 0.05), while the BMI of high L3-SMI group was (24.5±3.9) kg/m², significantly higher than that of low L3-SMI group [(20.5±2.9) cm²/m², P < 0.05]; the blood hemoglobin level in patiets with high L3-SMI group was (126.4±23.2) mmol/L, significantly higher than that in low L3-SMI group [(114.7±21.3) mmol/L, P < 0.05]; serum sodium in patients high L3-SMI group was (136.6±4.1)g/L, significantly higher than that in low L3-SMI group[(133.5±4.5)g/L, P <0.05]; serum total bilirubin level in patients with low L3-SMI group and high L3-SMI group were [(437.1±198.3)μmol/L and (317.4±173.0)μmol/L, respectively, P < 0.05]. Conclusion The level of L3-SMI in female patients, low weight patients, patients with liver cirrhosis and patients with alcoholic liver disease is lower. The level of L3-SMI in patients with ACLF is negatively correlated with the severity of the disease and has a certain correlation with the outcome of the patients, but the samples need to be further expanded to verify the correlation.

Key words: Acute-on-chronic liver failure, Clinical characteristics, Skeletal muscle index