Comparative Accuracy of Qualitative and Quantitative Contrast-Enhanced CT Analysis in Differentiating Intrahepatic Mass-Forming Cholangiocarcinoma from Colorectal Liver Metastasis

Objective: To compare the diagnostic performance of qualitative and quantitative computed tomography in differentiating intrahepatic mass-forming cholangiocarcinoma (IHMCC) from colorectal liver metastasis (CRLM).Material and Methods: A retrospective study analyzed 79 patients (IHMCC n=41, CRLM n=38). Two abdominal radiologists separately reviewed the following parameters: size, location, number, margin, calcification, hepatic capsular retraction, peripheral bile duct dilatation, proximal bile duct enhancement, extrahepatic spreading, regional lymph node enlargement, vascular and adjacent organ invasion, arterial and delayed enhancement. For the quantitative study, regions of interest were placed on lesions and adjacent liver in the non-contrast, portovenous and delayed phases. The percentage attenuation ratio, absolute percentage delayed enhancement, and the enhancement ratio on the portal venous and delayed phases (ERPV and ERD) were calculated. Multivariate logistic regression was used to determine the significant factors.Results: Ten qualitative features showed statistically significant differences. Satellite lesions (p-value<0.001), right hepatic lobe location (p-value=0.009), irregular margin (p-value=0.028), hepatic capsular retraction (p-value<0.001), peripheral bile duct dilatation (p-value<0.001), proximal bile duct enhancement (p-value=0.002), extrahepatic spreading (p-value=0.002), regional lymph node enlargement (p-value<0.001), vascular invasion (p-value<0.001), and adjacent organ invasion (p-value=0.01) were found more often in IHMCC versus CRLM. For quantitative analysis, size, ERPV, and ERD showed statistically significant differences (p-value=0.003 and p-value=0.001). Peripheral duct dilatation (OR 21.1,95% CI 5.07,77.7), regional node enlargement (OR 5.8, 95% CI 1.32, 26.085) and ERD (OR 4.4, 95% CI 1.02, 6.54) were significant predictors on multivariate analysis. From the ROC curve, an optimal cut-off of ERD was 0.79 (AUC0.704, 95% CI 0.59, 0.818). Conclusion: Peripheral bile duct dilatation, regional lymph node enlargement, and ERD greater than 0.79 can be useful in differentiating IHMCC from CRLM.