Ultrasonographic quantification of hepatic-renal echogenicity difference in hepatic steatosis diagnosis

Ultrasound (US) is recommended for hepatic steatosis screening. The purpose of this study was to determine the usefulness of US hepatic-renal echo-intensity (HR) difference in the quantitative assessment of hepatic steatosis.

Consecutive patients undergoing liver biopsy were prospectively enrolled. Using US histogram technique, the mean gray level of hepatic parenchyma and right renal parenchyma at selected regions of interest were evaluated on the same day of biopsy. With steatosis assessed by histology as the reference, the diagnostic performances of HR difference in predicting the degree of steatosis was analyzed. The optimal cut-off level, diagnostic validity and post-test probability were assessed.

A total of 175 patients were enrolled (M/F, 103/72; mean age, 48.6 ± 11.7). There were 64 (36.5 %), 42 (24 %), 29 (16.6 %), 12 (6.9 %) and 28 (16 %) patients with steatosis of <5, 5-9, 10-19, 20-29 and ≥ 30 %, respectively. Multivariate analysis showed HR difference correlated with the severity of steatosis (R (2) = 0.425, p < 0.001) with positive correlation between HR difference and the severity of steatosis (r = 0.60, p < 0.001). The diagnostic performances were 0.927, 0.890, 0.816 and 0.760 for steatosis ≥ 30, ≥ 20, ≥ 10 and ≥ 5 %, respectively. The cut-off is 7 for diagnosing steatosis ≥ 30 %, with a negative predictive value of 97.6 %. The cut-off is 4 in predicting steatosis ≥ 5 %, with a positive predictive value of 79 %. The prevalence of steatosis influenced the post-test probability.

Quantitative assessment of HR difference with US histogram technique is useful in excluding moderate to severe hepatic steatosis.