An endoscopic ultrasound is an advanced imaging test that focuses on tissues and organs within the digestive tract. It may be used to evaluate and stage various gastrointestinal cancers, to help your doctor visualize and diagnose bumps or nodules on the intestinal walls, to evaluate disorders associated with pancreatitis, or to visualize existing abnormalities regarding the liver and gallbladder. Using a flexible, lighted tube called an endoscope that is introduced via the mouth or rectum with the patient under sedation, the physician is able to get close-up and highly detailed images of various organs and tissues that are projected on a monitor. He or she can also extract a small tissue sample for biopsy at this time. The procedure typically takes from 30 to 90 minutes to perform and the patient can usually go home on the same day.