Endoscopic ultrasound (EUS)

Endoscopic ultrasound (EUS)

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.

Why it's done

EUS can create images of the lining and walls of any organ along the route of the gastrointestinal tract. An EUS device placed down the throat can capture images of the esophagus, stomach and parts of the small intestine. An EUS device inserted through the anus captures images of the rectum, parts of the large intestine (colon) and surrounding tissue such as lymph nodes.


Internal organs or nearby structures can also be visualized, including the following:

EUS with fine-needle aspiration or other instruments can also reach these other organs. For example, a needle can pass through the wall of the esophagus to nearby lymph nodes. Similarly, a needle can pass through the wall of the stomach to deliver medication to the pancreas.


EUS and EUS-guided procedures can be used for the following:


EUS is generally safe when performed at a centre with an experienced and expert health care team. The procedure is usually performed by a medical doctor who specializes in the digestive system (Medical gastroenterologist) and has specific training in EUS procedures.


Your doctor will discuss with you the risk of complications from EUS. These risks, which are most commonly associated with fine-needle aspiration, may include:

You can reduce your risk of complications by carefully following your doctor’s instructions for preparing for EUS.


Call your health care provider immediately or go to an emergency room if you experience any of the following signs or symptoms after the procedure:

What you can expect?

If you are given anaesthesia, you won’t be conscious during the procedure. If you’re given a sedative, you may feel a slight discomfort, but many people fall asleep or are not alert during the procedure.


You’ll likely lie on your left side during the procedure. The doctor feeds a thin, flexible tube (endoscope) through your throat or through your rectum, depending on the purpose of the procedure.


The endoscope has a tiny ultrasound transducer at the end. Any other instrument used during the procedure, such as a needle for a biopsy, also passes through a channel in the endoscope.


EUS usually lasts less than an hour. An EUS-guided procedure may last longer.


You may have a sore throat after an upper EUS procedure. Throat lozenges may provide relief.


A specialist in digestive diseases (gastroenterologist) or lung disease (pulmonologist) with special training in EUS will interpret the EUS images. A doctor trained in analysing biopsies (pathologist) will report the test results if you have fine-needle aspiration. Your doctor will discuss any important findings and next steps with you.