Comparison of sonographic hepatorenal ratio and the degree of hepatic steatosis in magnetic resonance imaging-proton density fat fraction

Objectives: Conventional ultrasonography can provide only semi-quantitative assessment of hepatic steatosis. The aim of this study was to assess sonographic hepatorenal ratio to quantify the severity of fatty liver. Methods: We performed a retrospective analysis of 179 patients with various liver diseases who underwent abdominal magnetic resonance imaging and ultrasonography on the same day. The hepatorenal ratio was calculated by the ratio between the mean echo intensity in regions of interests of the liver and regions of interests of the right renal cortex. Magnetic resonance imaging-proton density fat fraction was used as standard reference for steatosis grading. The effect of fibrosis measured by magnetic resonance elastography on the degree of correlation was also assessed. Results: The hepatorenal ratio was highly correlated with magnetic resonance imaging-proton density fat fraction (Spearman’s coefficient = 0.83) (p <0.001). High correlation of hepatorenal ratio with magnetic resonance imaging-proton density fat fraction was observed in patients with less than stage 2 fibrosis (p <0.001), whereas moderate correlation of hepatorenal ratio with magnetic resonance imaging-proton density fat fraction was found in patients with ≥ stage 2 fibrosis or higher (p <0.001). The hepatorenal ratio cutoff point for prediction of grade 1 hepatic steatosis was 1.18 with sensitivity of 90.0% and specificity of 80.0%. The hepatorenal ratio cutoff point for prediction of grade 2 and grade 3 hepatic steatosis was 1.55 and 1.60, respectively, with sensitivity greater than 90% and specificity greater than 80%. Conclusions: The hepatorenal ratio could become an effective quantitative tool for hepatic steatosis alternative to magnetic resonance imaging-proton density fat fraction. Application should be careful in the group of patients with stage 2 liver fibrosis or higher.