*3.1. Ultrasound*

Historically, the first report on using ultrasonography as a diagnostic tool in hepatic steatosis and steatohepatitis was published in 1981, in which patients suffering from alcohol-related disease were analyzed for parenchymal alterations, fatty infiltration, dilatation of hepatic veins and ascites [102]. Later studies have shown that the sensitivity of this radiologic modality is somewhat limited when the content of hepatic steatosis is below a certain threshold [103]. However, by use of this imaging technique, it was demonstrated in a prospective study investigating a cohort of 400 patients that the overall prevalence of NAFLD and NASH is significantly higher than originally estimated [104]. Based on these findings, the method is a significant diagnostic add-on for screening of patients at risk for NAFLD and NASH, in particular when liver enzymes are elevated. In line with this assumption, a very recent descriptive, cross-sectional study categorizing 109 patients into different grades of NAFLD by ultrasonography showed that ultrasound is still an important, cheap, and easy-to-use imaging tool for the diagnosis and grading of fatty liver diseases [105]. In addition, the authors could demonstrate that ultrasound is ideally suited to manage patients with fatty liver in follow-ups, because of its significant association with deranged lipid profiles and the lack of any side effects.

Contrast-enhanced ultrasound (CEUS) allowing to monitor not only qualitatively, but also quantitative analysis of lesion microcirculation has helped to establish diagnostic procedures for detection of focal and diffuse liver pathologies and to assess a differential diagnosis between benign and malignant liver lesions [106].
