MRI for Intrahepatic Bile Duct Adenoma: A Diagnostic Comparative Study with Intrahepatic Cholangiocarcinoma

Discrimination of intrahepatic bile duct adenoma (iBDA) particularly from small intrahepatic cholangiocarcinoma (iCCA) is challenging yet clinically crucial to prevent unnecessary overtreatment. We aimed to investigate the MRI characteristics of iBDA, and the key features to differentiate from iCCA.

A total of 36 patients with pathologically-confirmed iBDA (27 men and 9 women) and 53 patients with pathologically-confirmed small iCCA≤20 mm (39 men and 14 women) were retrospectively included. MRI features were analyzed and compared; univariate and multivariate analyses were performed to identify independent imaging predictors for BDA. A combined nomogram was established, with diagnostic performance assessed by receiver operating characteristic curve analysis, calibration and decision curves.

iBDA typically appeared as small, round, subcapsular lesions, showing high or slightly high T2-weighted signal intensity with central darkness, arterial rim hyperenhancement with persistent enhancement pattern, high or iso-signal intensity on both diffusion-weighted image and apparent diffusion coefficient (ADC) map. Multivariate analysis identified round shape (odds ratio=59.623, P=0.001), T2-weighted central darkness (odds ratio=24.151, P=0.012), and no diffusion restriction on ADC map (odds ratio=7.751, P=0.013) as independent predictors favoring iBDA over iCCA. The combined index demonstrated excellent performance (AUC=0.951[95%CI 0.913-0.989]), with high sensitivity, specificity and accuracy of 88.9%, 88.7% and 88.8%. Calibration and decision curves demonstrated good agreement and optimal net benefit.

Characteristic MRI features of iBDA enabled differentiation from iCCA. The combination of imaging features including round tumor shape, T2-weighted central darkness, and no diffusion restriction can potentially serve as a reliable, non-invasive tool to achieve accurate diagnosis and guide appropriate clinical decision-making.