Comparison of CT findings of biliary tract changes with autoimmune pancreatitis and extrahepatic bile duct cholangiocarcinoma

Purpose To retrospectively evaluate criteria for differentiating biliary tract changes in autoimmune pancreatitis (AIP-BTC) from extrahepatic cholangiocarcinoma (ECCA) based on CT findings and to determine predictors for differentiation between the two disorders. Materials and methods CT findings of 22 patients with AIP-BTC and 45 patients with ECCA, both with positive CT findings in the biliary system, were retrospectively assessed. The images were assessed for presence of biliary obstruction, diameter of the maximally dilated biliary duct, maximum thickness of the involved duct, presence of masses inside or around the involved ducts, lengths of the biliary lesions, concentricity of wall thickening, multifocality of the lesion, and degree of lesion enhancement. Results Compared with AIP-BTC, ECCA was significantly more frequently associated with biliary obstruction (p = 0.0037), shorter lengths of the biliary lesions (p = 0.0036), and masses (p > 0.001). No significant differences were found for other items. Conclusion Presence of obstructive dilatation of the bile ducts and intraluminal or peri-ductal masses and length of the thickened wall may help differentiate between AIPBTC and ECCA.