Value and Limitations of Non-invasive Liver Assessment in Obesity: A Biopsy-Controlled Study in Metabolic Bariatric Surgery

Abstract Background Metabolic-associated steatotic liver disease (MASLD) is frequent in patients with obesity, ranging from steatosis to cirrhosis. Accurate preoperative assessment of hepatic steatosis and fibrosis is essential to identify high risk patients, optimize surgical selection and guide follow-up. Aims The aim of the present study was to evaluate diagnostic accuracy of FIB-4 score and preoperative liver elastography for detecting severe fibrosis and steatosis in metabolic bariatric surgery (MBS) patients. Methods All patients undergoing MBS in our center between 01.2024 and 12.2024 with an available liver biopsy were included. Preoperative FIB-4 and elastography parameters (liver stiffness kPa and CAP dB/m) were assessed for association with severe fibrosis (SF, defined as F3-F4) and steatosis. Spearman’s coefficient assessed correlation between continuous variables; ROC curve analysis with Youden’s index identified optimal thresholds. Multivariable logistic regression was performed to identify independent predictors of SF. Results Overall, 86 patients were included in the study (51.2% female), with a mean age of 43±11.2 years and a mean BMI of 44.6±8.4 kg/m2. In multivariable analysis, only increased FIB-4 score (OR 25.8,95%CI 2.8-241.1, p=0.004) remain independently associated with histologically proven SF; a FIB-4 threshold of ≥0.625 was associated with SF (AUC=0.790). Baseline ARFI and liver stiffness were not predictive of SF, whereas CAP was significantly associated with severe steatosis (p=0.042), with an optimal threshold of≥322.5 dB/m. After a median postoperative follow-up of 18months (95%CI 10.4-25.6), FIB-4 remained comparable to pre-surgical levels, without correlation with weight loss. Liver stiffness showed a significant decrease (pre-operative 9.7±6.7 kPa, post-operative 5.6±1.3 kPa, p=0.044). Similarly, CAP decreased from 333.7±64.6 to 210.1±89.2 dB/m (p=0.010). Conclusion FIB-4 score and elastography provide complementary information for preoperative assessment of MASLD in surgical candidates. Postoperative improvements in elastography-derived stiffness and CAP reflect the metabolic benefits of surgery on liver disease.