Cholangiocarcinoma and Malignant Biliary Obstruction 81

Cholangiocarcinomas (CC) are malignant neoplasms arising from biliary epithelium. Although it is an uncommon malignancy, it is the second most common primary hepatobiliary malignancy and the incidence is increasing globally (Malhi and Gores 2006). CC can be classified according to anatomic location as intrahepatic or extrahepatic, with extrahepatic further classified as hilar and distal extrahepatic. Familiarity with the diverse imaging and clinical manifestations depending on different morphologic types of CC is important for accurate diagnosis and assessment of resectability. The morphologic classification proposed by the Liver Cancer Study Group of Japan (Yamasaki 2003) classifies intrahepatic CC as mass-forming, periductal-infiltrating, and intraductal-growing types. Risk factors for CC include primary sclerosing cholangitis (PSC), chronic hepatolithiasis, recurrent pyogenic cholangitis (RPC), choledocholithiasis, parasitic biliary infestation, viral hepatitis, bile duct adenoma, biliary papillomatosis, Caroli’s disease, choledochal cyst, Thorotrast, smoking, and chronic typhoid carrier state. However, in many cases, no risk factor is identified. PSC is a common risk factor for the development of CC in Western countries (Burak et al. 2004), whereas parasitic infestation by Clonorchis sinensis and Opisthorchis viverrini (Kim et al. 2006, 2007) and RPC (Kim et al. 2006) are important risk factors in the East and Southeast Asia. Chronic hepatitis B and C virus infections have recently been recognized as risk factors for intrahepatic CC in both the East and West (Malhi and Gores 2006). Radiological imaging plays a crucial role in the diagnosis and staging of CC and malignant biliary obstruction. Ultrasound is often used as the initial imaging test for suspected biliary obstruction. CT is most commonly used for the diagnosis and staging of the disease as well as follow-up. MR imaging is often helpful as an adjuvant imaging modality as it can provide superior tissue characterization and highquality noninvasive cholangiography. In practice, a multimodality approach is helpful for challenging cases. This chapter reviews typical imaging patterns of CC and other causes of malignant biliary obstruction on cross-sectional imaging.