Quantitative measurement of ultrasound attenuation and hepato-renal index in non-alcoholic fatty liver disease

Abstract

Objective: The aim of this study was to non-invasively explore new methods of ultrasound attenuation measurements in livers of patients with Non-Alcoholic-Fatty-Liver-Disease (NAFLD) and to measure the liver tissue elasticity. Material and method: Sixteen patients with NAFLD, twelve patients with liver fibrosis and fifteen healthy subjects were included. Echo Levels (ELs) in dB were measured at 2 and 7cm depths in the right liver to calculate the attenuation. ELs were measured in liver and right kidney tissue to calculate the Hepato-Renal Index (HRI). This index was calculated both as a difference, HRIdiff; (EL Liver-EL Kidney) and HRI-ratio; (EL Liver / EL Kidney) using built-in software of the ultrasound scanner. Liver tissue elasticity was measured using transient elastography (TE, Fibroscan®). NAFLD and liver fibrosis were confirmed by liver biopsy. Results: We found that HRI- diff was significantly higher in the NAFLD group compared with healthy subjects, 6.2 dB (0.8-11.4) vs.1. 9 dB (0.0-6.1), p=0.012. HRI- ratio was significantly lower between the same two groups, 0.9 dB (0.8- 1.02) vs.1.01 dB (0.9-1.12), and p<0.0001. TE, ELs and liver size showed significant differences between NAFLD patients and healthy controls. Between patients with fibrosis and NAFLD the differences were significant for TE, liver size and attenuation. Intra- and interobserver correlation and agreement of ELs were good. Conclusion: Measurements of liver tissue using HR-Indexes, ultrasound attenuation, and tissue elasticity may be useful methods to differentiate objectively between steatosis and healthy and quantify the differences.