BACKGROUND. Contrast-enhanced ultrasound (CEUS) LI-RADS assigns category LR-M to observations that are definitely or probably malignant but that on imaging are not specific for hepatocellular carcinoma (HCC). A high percentage of LR-M observations represent HCC. OBJECTIVE. The purpose of this study was to retrospectively evaluate the utility of additional features, beyond conventional LI-RADS major features, for detecting HCC among LR-M observations on CEUS. METHODS. This retrospective study included 174 patients (145 men, 29 women; mean age, 53 years) at high risk of HCC who underwent CEUS from August 2014 to June 2016 that showed an LR-M observation according to CEUS LI-RADS version 2017. Two radiologists independently assessed CEUS images for major features and four additional features (chaotic vessels, peripheral circular artery, clear boundary of tumor enhancement, clear boundary of intratumoral unenhanced area). The diagnostic performance of four proposed criteria for the detection of HCC among LR-M observations was assessed. The impact of criteria based on the additional findings on detection of HCC was further explored. Histology or composite imaging and clinical follow-up were the reference standards. RESULTS. The 174 LR-M observations included 142 HCCs and 32 non-HCC lesions (20 intrahepatic cholangiocarcinomas, five combined hepatocellular-cholangiocarcinomas, seven benign lesions). Interreader agreement on the additional features ranged from κ = 0.65 to κ = 0.88. Two of the additional features had excellent PPV for HCC: chaotic vessels (94.8%) and peripheral circular arteries (98.1%). The presence of either of these two additional features had sensitivity of 50.7%, specificity of 90.6%, PPV of 96.0%, and NPV of 29.3% for HCC. Three other criteria incorporating variations of major LI-RADS features but not the additional features had sensitivities of 55.6-96.5%, specificities of 49.6-68.8%, PPVs of 87.8-90.6%, and NPVs of 25.0-75.0%. On the basis of criteria that included additional features, 75 of 174 LR-M observations were recategorized LR-5; 72 of the 75 were HCC. CONCLUSION. The presence of chaotic vessels and/or peripheral circular artery had high specificity and PPV for HCC among LR-M observations. Other explored criteria based on major features did not have higher specificity or PPV. CLINICAL IMPACT. Clinical adoption of the additional CEUS features could help establish the diagnosis of HCC noninvasively and avoid the need for biopsy of LR-M observations.
Keywords: contrast-enhanced ultrasound; hepatocellular carcinoma; intrahepatic cholangiocarcinoma.