EUS is a procedure done to examine the walls of the upper and lower gastrointestinal tract and to study other organs that are nearby including the lungs, liver, gallbladder and pancreas.

The endoscopist will use a thin, flexible tube that has a built-in miniature ultrasound probe and will pass it through the mouth or anus to the area to be examined. He will then shift to the ultrasound using sound waves to create visual images of the digestive tract.

EUS is used to evaluate known abnormalities, including lumps or lesions, which were detected at a prior endoscopy or imaging. It can help the doctor determine the origin and help treatment decisions. EUS can be used to diagnose diseases of the pancreas, bile duct and gallbladder when other tests are inconclusive or conflicting. It also helps determine the extent of spread of certain cancers of the digestive and respiratory systems. It can be used as well to obtain a needle biopsy of a lump or lesion to guide treatment.

For EUS of the upper gastrointestinal tract, the patient should have nothing to eat or drink, usually for six hours before the examination.

For EUS of the rectum or colon, either a colonic cleansing solution orally or an enema rectally is given prior to the procedure.

Although complications can occur, they are rare. Bleeding might occur at a biopsy site, but it is usually minimal and rarely requires follow-up. One major but very uncommon complication of EUS is perforation.