Biliary malignancies: multi-slice CT or MRI?

Cholangiocarcinoma is the most common malignant bile duct and the second most common primary malignant tumor in the liver. It can be classified as intrahepatic (peripheral) or extrahepatic. Extrahepatic cholangiocarcinoma originate most often from the main hepatic duct and confluence (referred to as Klatskin tumor). The patients usually present with jaundice because of biliary obstruction. Prognosis of hilar cholangiocarcinoma is poor, because most tumors are not resectable at the time of diagnosis. Surgical exploration should only be undertaken when there is potential for curative resection shown by imaging. ERCP (endoscopic retrograde cholangio-pancreatography) demonstration of Klatskin tumors is often incomplete due to incomplete ductal filling. MR imaging and helical CT are the methods of choice in the diagnosis and staging of hilar cholangiocarcinoma. MR cholangiography, in conjunction with MR imaging and MRA, provides information on tumor size, bile duct involvement, and vascular compromise, and thus resectability of the tumor. Multi-phasic contrastenhanced thin-section helical CT may show Klatskin tumors with a sensitivity of up to 100%. Tumors are better seen on arterial-dominant phase than on portal venous phase scans (sensitivity, 100% vs. 86%). However, single-slice CT is not accurate for assessing resectability (accuracy, 60%), because proximal tumor extent is largely underestimated. Preliminary experience with multi-slice CT indicates that the extent of bile duct involvement may be better displayed due to multi-planar imaging capabilities. Curved planar reconstruction of multi-slice CT data sets along the portal vein and the bile ducts reveals tumor involvement. Intrahepatic cholangiocarcinoma have a non-specific imaging appearance. Because of abundant fibrous stroma, they exhibit little contrast enhancement during CT or MR imaging scanning in the early phase with delayed accumulation of contrast material. Although not pathognomonic, the presence of bile duct dilatation within the tumor and retraction of the liver capsule adjacent to the tumor are suggestive of the diagnosis. In conclusion, the role of contrast-enhanced MR imaging with MR cholangiography and multi-slice CT in the detection and preoperative staging of cholangiocarcinoma is emphasised.