A convex EUS is useful to diagnose vascular invasion of cancer, especially hepatic hilus cancer.

Endoscopic ultrasonography (EUS) has become an indispensable diagnostic procedure pairing endoscopy with transluminal high frequency ultrasonography. EUS provides images with a high resolution such that the depth of tumor invasion can be accurately determined. It also sees lesions outside of gastrointestinal tract, particularly those in pancreas, biliary system and periluminal lymph nodes. The most important limitation of EUS was lack of specificity, that is, the differentiation between benign and malignant lesions. In 1992, EUS-guided fine needle aspiration (EUS-FNA) was introduced with the sampling of a lesion in the pancreatic head using a convex EUS. Since then the indications of EUS-FNA have been expanded to include a variety of therapeutic uses. In addition, a convex EUS probe can also be used for detailed evaluation of the pancreatobiliary system, in lieu of a radial EUS. The vascular structures surrounding liver, biliary system and pancreas can be showed by a convex EUS system very clearly and easily compared with the more familiar radial EUS images. So we think a convex EUS is very useful for not only EUS-FNA but also screening and close examination for cancer with vascular invasion.