Quantifying changes in steatotic liver disease after bariatric surgery using ultrasound-derived fat fraction

Background A noninvasive, readily accessible, and quantitative methods are needed to evaluate changes in hepatic fat over time in patients undergoing bariatric surgery. Purpose To measure the change in ultrasound-derived fat fraction (UDFF) in severely obese adults before and after bariatric surgery. Materials and Methods Participants undergoing bariatric surgery were prospectively enrolled at a single center and evaluated at 3 time points: pre-surgery (before a 2-week pre-operative liquid diet), day of surgery (immediately following the liquid diet), and 6 months post-surgery. Measurements included UDFF (Siemens Healthineers ACUSON SEQUOIA), skin-to-liver capsule thickness, serum metabolic tests, liver function tests, and anthropometric data. Changes in these variables were analyzed using 2-sided paired t-tests. Pearson correlation analysis was used to evaluate associations between changes in UDFF and changes in skin-to-capsule thickness, waist circumference, and BMI. Results Seventeen participants (mean age 47.41 ± 11.11 years, 15 women) completed the study. UDFF (mean ± SD) decreased significantly from 20.4 ± 8.41% pre-surgery to 11.08 ± 6.33% at 6 months post-surgery (P < .001). Skin-to-liver capsule thickness decreased from 4.06 ± 0.66 cm to 2.88 ± 0.55 cm (P < .001). BMI decreased from 46.27 ± 6.65 kg/m2 to 35.5 ± 6.64 kg/m2 (P < .001), and waist circumference decreased from 130.29 ± 13.49 cm to 111.98 ± 16.03 cm (P < .001). No significant changes were observed in UDFF, skin-to-liver capsule thickness, or waist circumference after the liquid diet phase. Strong positive correlation between UDFF and BMI reduction was observed (r = 0.75, P < .001). Conclusions Bariatric surgery results in significant reductions in hepatic steatosis, as measured by UDFF, and reductions in skin-to-liver capsule thickness, BMI, and waist circumference at 6 months post-surgery. These findings suggest that UDFF could meet the clinical need for noninvasive monitoring of hepatic steatosis following bariatric surgery.