Endoscopic ultrasound (EUS) is a minimally invasive imaging technique that uses sound waves to create a computer image of the inside of the esophagus and stomach. The endoscope is guided into the mouth and throat, then into the esophagus and the stomach. As in standard endoscopy, this allows the physician to view the inside of this area of the body, as well as insert instruments to remove a sample of tissue (biopsy).
Endoscopic ultrasound is most commonly used to diagnose and stage cancers. EUS is very effective at visualizing the individual layers of the gastrointestinal tract, which aids in the detection of precancerous lesions and early-stage cancerous lesions of the esophagus, stomach and rectum. EUS can be used to help physicians determine if cancer has spread to nearby lymph nodes and to detect tumors present in other organs, such as the pancreas, lungs, and bile duct.