Fade-out sign on hepatic tissue harmonic compound sonography: A value as a new sign in the diagnosis of fatty liver

Abstract

To evaluate the value of the fade-out sign in the diagnosis of fatty liver (FL) on hepatic ultrasound (US). We evaluated 127 patients who underwent hepatic US, including 70 patients with FL and 57 normal control subjects. US images were qualitatively evaluated for the presence of the fade-out sign. This sign was considered present if there was a dark band on the deep portion of the liver on the harmonic image when compound sonography (CS) was converted to tissue harmonic CS mode. The degrees of FL were classified into mild, moderate, and severe. The distribution of lengths of dark bands in three groups was examined, and a multiple comparison of the average dark band length was carried out using one-way ANOVA. The fade-out sign was seen in 55 of 70 FL patients (78.6%) compared to 3 of 57 control subjects (5.3%) (p<0.001). The sensitivity, specificity, accuracy, and positive predictive value of the fade-out sign for the US diagnosis of FL were 78%, 94%, 85.8%, and 94.8%, respectively. Among the 70 FL, there were 28 mild FL (mean length of dark band; 8.3 mm±8.2), 31 moderate FL (mean; 28 mm±6.3), and 11 severe FL (mean; 51 mm±8.3). There were significant differences in band length according to severity (p<0.01). The fade-out sign on hepatic harmonic US was frequently present in FL. As fat infiltration increased, the fade-out sign lengthened. The fade-out sign offers a specific and new sign of FL.