8 - Early Bile Duct Carcinoma: Ultrasound, Computed Tomography, Cholangiography, and Magnetic Resonance Cholangiography

Abstract

Early bile duct cancer is defined as carcinoma limited to the mucosa or fibromuscular layer of the bile duct. These tumors have no lymph node metastasis, venous invasion, perineural, or lymphatic infiltration. Radiological diagnosis of early bile duct carcinoma is important because patients with early bile duct cancer, if resected, have an excellent prognosis, the cumulative 5-year-survival rate being 83-100%. Tumors may arise anywhere in the bile ducts (intrahepatic, hilar, or extrahepatic ducts) and present with nodular, polypoid, cast-like appearances and vary in size from 1 to 5 cm or larger. The tumor-bearing fibromuscular layer may be thickened, varying from 1.5 to 2.0 mm. The tumor is papillary adenocarcinoma, well-differentiated tubular adenocarcinoma, or well-differentiated papillotubular adenocarcinoma. Computed tomography shows an intraductal soft tissue mass with varying size. In patients with intrahepatic and hilar cholangiocarcinoma, the outer margin of the tumor-bearing bile duct is usually not distinctly delineated due to lack of intrahepatic periductal fat or partial volume averaging. In some patients, the bile duct is enhanced as a thin tube or ring on contrast-enhanced CT images. On cholangiograms, the size, shape, and extent of tumors are well demonstrated. The outer surfaces of tumor-bearing bile ducts are irregular due to the papillary surface of the tumor per se. It is not possible to evaluate whether or not the tumor involves the outer surface of the bile ducts.