Endoscopic ultrasonography is an endoscopic test similar to upper or lower endoscopy that involves a dedicated ultrasound probe at the end of the scope to allow for visualization of structures outside the GI tract. Typically, EUS is used for cancer diagnosis and staging, assessment of lymph nodes, and evaluation of pancreatic diseases and small lesions under the surface of the lining of the GI tract. While EUS is a minimally invasive procedure with an endoscopist who has undergone appropriate training, it can be extremely useful in diagnosing and assessing certain conditions if or when other imaging methods may not be as useful.