The Degree of Contrast Washout on Contrast-Enhanced Ultrasound in Distinguishing Intrahepatic Cholangiocarcinoma from Hepatocellular Carcinoma

We aim to assess the role and degree of contrast washout in the differential diagnosis of intrahepatic cholangiocarcinoma (ICC) from hepatocellular carcinoma (HCC) on contrast-enhanced ultrasound (CEUS). Fifty-six histopathology-confirmed ICC nodules and 184 HCC nodules were included in this study. The nodules' washout degree on CEUS at 1, 2 and 3 min was semi-quantitatively and qualitatively assessed using gray-scale video signal intensity. Semi-quantitative assessment showed that the washout degree of ICCs at 1, 2 and 3 min were significantly lower than those of HCCs (p < 0.001) and similar results were found in the same size range subgroups. There were no significant differences in the washout degree of ICCs between patients with chronic hepatitis and those without. The areas under receiver operating characteristic curves, using the nodules' washout degree at 1, 2 and 3 min to differentiate ICC from HCC, were 0.957, 0.979 and 0.982, respectively. The qualitative assessment showed the washout of ICCs was more rapid and obvious than that of HCCs. At 3 min, moderate and marked washout were observed in all ICCs, but in only 12.5% HCCs (p < 0.001). In conclusion, ICCs displayed much higher degree of contrast washout than HCCs on CEUS, which allowed for differentiation from HCCs.