Alterations in the Liver Fat Fraction Features Examined by Magnetic Resonance Imaging Following Bariatric Surgery: a Self-Controlled Observational Study

Background: Obesity is a worldwide epidemic leading to non-alcoholic fatty liver disease. Alterations in the liver fat fraction (LFF) assessed by MRI following bariatric surgery is a promising feature; however, few studies have been fully elucidated.

Purpose: To determine the alterations in the LFF features following surgery using MRI, to determine the correlation with the clinical non-alcoholic steatohepatitis score (C-NASH score), and to identify the predictive factors for postoperative score changes.

Methods: Patients (n = 69) underwent MRI to measure the LFF at baseline and 3 months postoperatively. Paired sample t tests were applied to investigate the alterations in the major parameters. Univariate analyses were performed to evaluate the factors predicting C-NASH score changes after surgery.

Results: Compared with the baseline levels, the LFF significantly decreased 3 months postoperatively (P < 0.001). Significant positive correlations were detected between the C-NASH score and LFF levels (P < 0.001). Among the ROC curves for C-NASH score change, the AUC for the ROC curve of LFF was 0.812 (95% CI 0.707, 0.916) and the cut-off value was 6.16%. Weight at baseline was a significant predictive factor for postoperative changes when the C-NASH score was ≥ 3 (P < 0.001). The AUC for the ROC curve of weight was 0.897 (95% CI 0.782, 1.000) and 117 kg was the cut-off value.

Conclusions: LFF decreased following bariatric surgery, which predicted C-NASH score changes after surgery. For patients with a higher risk of NASH (score ≥ 3) at baseline and lower preoperative body weight, we noted significantly greater effects of surgery on score change value.