Endoscopic ultrasound (EUS) is a minimally invasive procedure to assess diseases of the digestive (gastrointestinal) tract and other nearby organs and tissues. Endoscopic ultrasound combines the use of a thin, flexible tube (endoscope) inserted into the gastrointestinal tract and a device that uses sound waves to create images (ultrasound).

The high-frequency sound waves produce detailed images of the digestive tract and surrounding organs and tissues, including the lungs, pancreas, gall bladder, liver and lymph nodes.

An endoscopic tube may also have a small needle to remove fluid or tissue samples (biopsy) for examination in a lab. This procedure is called EUS-guided fine-needle aspiration or EUS-guided fine-needle biopsy. Other EUS-guided procedures can be used to drain fluid from a lesion or inject a drug at a specific site.