Role of Endoscopic Ultrasonography in the Evaluation of Extrahepatic Cholangiocarcinoma

Cholangiocarcinoma is a malignancy that arises from biliary epithelium and is associated with a poor prognosis. Accurate preoperative diagnosis and staging of cholangiocarcinoma continues to remain difficult. Endoscopic retrograde cholangiopancreatography (ERCP) is the most commonly performed procedure for cholangiocarcinoma and can provide a tissue diagnosis through brush cytology of the bile duct. However, the sensitivity of biliary brush cytology to diagnose cholangiocarcinoma may be as low as 30%. Endoscopic ultrasound (EUS) is a diagnostic modality which may overcome the limitations of other imaging and biopsy techniques in this setting. BUS can complement the role of ERCP and provide a tissue diagnosis through fine needle aspiration (FNA) and staging through ultrasound imaging. There is currently a paucity of data about the exact role of BUS for the diagnosis of cholangiocarcinoma in patients with indeterminate extrahepatic biliary strictures. Although multiple studies have shown that BUS is more accurate than ERCP and radiologic imaging for identifying a biliary mass and diagnosing cholangiocarcinoma, the sensitivities are variable. More importantly, the incidence of false negative results is not negligible, though the specificity is close to 100%. There is also controversy regarding the role of BUS-FNA, since even though this may increase diagnosis, it can also lead to tumor seeding.