Comparison of Non-invasive Methods for Diagnosis of Non-alcoholic Fatty Liver Disease Before Bariatric Surgery and Postoperative Follow-up in Obese Patients.

Purpose: This study aims to identify the most accurate and useful non-invasive method to replace liver biopsy for the diagnosis of non-alcoholic fatty liver disease (NAFLD) before bariatric surgery and postoperative follow-up in morbidly obese patients.

Materials and methods: This single-center study is a retrospective analysis of prospectively collected data from 68 morbidly obese patients who underwent laparoscopic sleeve gastrectomy with intraoperative liver biopsy. Preoperative non-invasive diagnostic methods, including fatty liver index, NAFLD fibrosis score, enhanced liver fibrosis score, FibroScan, magnetic resonance imaging-proton density fat fraction (MRI-PDFF), magnetic resonance spectroscopy (MRS)-PDFF, and magnetic resonance elastography (MRE) were compared against liver biopsy results. Diagnostic performance was assessed using Spearman's correlation and receiver operating characteristic (ROC) curve analysis.

Results: Liver biopsy confirmed the presence of steatosis in 92.7% of patients, Nonalcoholic Steatohepatitis (NASH) in 64.7%, and liver fibrosis (≥F1) in 72.0%. MRI-PDFF and MRS-PDFF demonstrated the highest diagnostic accuracy for NASH, with the strongest correlation with histological findings. For liver fibrosis, MRE showed the strongest correlation with histological fibrosis stage, while FibroScan-Liver Stiffness Measurement (LSM) demonstrated better diagnostic performance in ROC analysis. However, the overall diagnostic quality of non-invasive methods for fibrosis assessment remained modest, with no method achieving a quality value above 0.6.

Conclusion: MRI-PDFF and MRS-PDFF were the most accurate noninvasive methods for diagnosing NASH in morbidly obese patients. For liver fibrosis, FibroScan-LSM may be more suitable for detection, while MRE may better reflect fibrosis severity. Further studies are needed to assess the cost-effectiveness and clinical applicability of these methods.