Utility of convex EUS for preoperative vascular evaluation of malignant biliary tract neoplasm

The aim of the present study was to examine the utility of convex endoscopic ultrasonography (EUS) for the preoperative vascular evaluation of malignant biliary tract neoplasm, by comparing EUS findings with histological findings from resected specimens. Between January 2008 and January 2016, the present study retrospectively retrieved 82 cases diagnosed with malignant biliary tract neoplasm to compare findings from convex EUS with histological findings from resected specimens. A total of four groups were defined according to the results of EUS of the hepatic artery (HA) and portal vein (PV): Group 1, hyperechoic tissue between tumor and vessel; group 2, close proximity between tumor and vessel without loss of hyperechoic tissue; group 3, tumor and vessel contiguity, with loss of hyperechoic tissue; and group 4, encasement >180°. Regarding the HA, all 17 cases in groups 2 and 3 in which the tumor was close to the HA however no obvious encasement was evident, demonstrated no histological invasion, or the HA could be separated from the tumor intraoperatively. However, this was not the case for the portal vein. Of the six cases in group 3, 4 cases (66.7%) demonstrated PV invasion. Overall, convex EUS is useful for the preoperative evaluation of malignant biliary tract neoplasms, and surgery may be considered when the tumor is close to the HA on computed tomography scans, however there is no obvious encasement visualized by convex EUS.