Endoscopic ultrasound (EUS) is a procedure that can visualize and take tissue samples of lesions from many organs, including the esophagus, stomach, small and large intestines, bile ducts, pancreas, and liver. It can also help determine the stage of many cancers of the digestive system. It is performed under sedation with an endoscope, which is a long flexible tube with a light, camera, and ultrasound probe attached. It is generally a safe procedure, although complications such as bleeding, infection, and tearing of the digestive tract can rarely occur.