Hepatorenal index for grading liver steatosis with concomitant fibrosis

Ultrasonography is widely used as the first tool to evaluate fatty liver disease, and the hepatorenal index is a semi-quantitative method that improves its performance. Fibrosis can co-exist with steatosis or even replace it during disease progression. This study aimed to evaluate the influence of fibrosis on the measurement of steatosis using the hepatorenal index.

This cross-sectional study included 89 patients with nonalcoholic fatty liver disease and in whom liver fibrosis was determined by ultrasound elastography. The Pearson's correlation coefficient was used to compare between the results of the sonographic hepatorenal index and the quantification of steatosis using magnetic resonance spectroscopy as well the accuracy of detecting moderate to severe steatosis using sonography in two groups of patients: (A) without advanced fibrosis and (B) with advanced fibrosis. Advanced fibrosis was defined as a shear wave speed ≥ 1.78 m/s on ultrasound elastography. We calculated the area under the curve (AUC-ROC) to detect the ability of the hepatorenal index to differentiate light from moderate to severe steatosis in both groups. Moderate to severe steatosis was defined as a fat fraction > 15% on the magnetic resonance spectroscopy. The intra-observer variability was assessed using the Bland-Altman plot.

Among patients, the mean age was 54.6 years and 59.6% were women, 50.6% had a body mass index ≥ 30 kg/m2, 29.2% had moderate to severe steatosis, and 27.2% had advanced fibrosis. There was a correlation between steatosis grading by ultrasonography and magnetic resonance in group A (0.73; P < 0.001), but not in Group B (0.33; P = 0.058). The AUC-ROC for detecting a steatosis fraction ≥ 15% was 0.90 and 0.74 in group A and group B, respectively. The intra-observer variability for the hepatorenal index measurements was not significant (-0.036; P = 0.242).

The hepatorenal index is not appropriate for estimating steatosis in livers with advanced fibrosis.