To compare the consistency and diagnostic performance of contrast-enhanced ultrasound (CEUS) versus gadoxetic acid-enhanced magnetic resonance imaging (EOB-MRI) in liver imaging reporting and data system (LI-RADS) classification of focal liver lesions ≤3 cm in patients at high risk of hepatocellular carcinoma (HCC).

Patients with focal liver lesions ≤3 cm at high risk of HCC who underwent CEUS and EOB-MRI at Tianjin Third Central Hospital were prospectively collected. The CEUS and EOB-MRI images of each liver nodule were observed to evaluate interobserver consistency using kappa coefficient and category according to the CEUS LI-RADS V2017 and CT/MRI LI-RADS V2018 criteria in a double blind manner. Pathology was used as the reference standard of malignant lesions and pathology and/or follow-up results were used as the reference standard for benign lesions to calculate the diagnostic performance of the two modalities, and χ² test and Z test were used to compare the difference between the two modalities.

A total of 114 nodules of 107 cases met the inclusion criteria. The proportions of LR-5, LR-4, LR-3, and LR-M diagnosed by CEUS and EOB-MRI accounted for 45.6%, 11.4%, 19.3%, and 23.7%, and 25.4%, 57.9%, 10.5%, and 6.1%, respectively. The consistency of nodule classification between the two modalities was poor (Kappa=0.17, P<0.001). There was good consistency between readers on CEUS LI-RADS and EOB-MRI LI-RADS (Kappa=0.83 and 0.77, P<0.001). The positive predictive values of CEUS and EOB-MRI LR-5, LR-4, and LR-3 for HCC were 98.1%, 38.5%, and 13.6%, and 100%, 71.2%, and 16.7%, respectively. The sensitivity, specificity, and area under the curve (AUC) of CEUS and EOB-MRI LR-5 for HCC were 64.6%, 97.1%, and 0.81, and 36.7%, 100%, and 0.68, respectively. The was no statistical difference in the positive predictive value or specificity between the two groups, while the difference of AUC was statistically significant (Z=4.29, P<0.01).

CEUS and EOB-MRI have poor consistency in classification of liver nodules ≤ 3 cm. The consistency between readers is good. CEUS and EOB-MRI LR-5 have equally good diagnostic performance for HCC ≤ 3 cm.