Endoscopic ultrasound (EUS)

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was reviewed on June 13, 2022.

An endoscopic ultrasound (EUS) is a diagnostic procedure that combines an endoscopy and ultrasound in order to take detailed pictures of any or all of these body parts:

  • Small intestine
  • Esophagus
  • Stomach
  • Pancreas
  • Gallbladder
  • Lymph nodes
  • Bile ducts

During the test, an endoscope (a thin, lighted tube with a camera and ultrasound probe on one end) is inserted into the body either through your mouth or anus. The endoscope then uses sound waves to create detailed images of your internal structures on a live computer screen.

There are two types of endoscopic ultrasounds:

An upper endoscopic ultrasound examines the upper gastrointestinal tract, including the esophagus, stomach, small intestine, pancreas, gallbladder and bile ducts, as well as nearby lymph nodes, blood vessels and any tumors. In this case, the endoscope is carefully guided into the mouth, down the throat and into the body.

A lower endoscopic ultrasound is used to examine the inside of the rectum and colon, as well as the bladder, prostate and uterus, plus nearby lymph nodes and any tumors. In this case, the endoscope is carefully guided through the anus and into the body.

The procedure may be performed to investigate the cause of symptoms you may be having, including:

  • Difficulty swallowing
  • Indigestion
  • Feeling full after eating very little
  • Coughing up or vomiting blood

Or, an EUS may be performed if previous imaging tests have indicated abnormalities in any of the areas of the body mentioned earlier.

If a biopsy is needed, a needle can be guided through the endoscope at this time to collect a sample.

Why an endoscopic ultrasound is done

If your doctor has conducted other diagnostic tests—such as an endoscopy, colonoscopy, X-ray or computed tomography (CT) scan—and a suspicious area such as a lesion or tumor was discovered in the walls of the gastrointestinal tract, the next step may be to perform an endoscopic ultrasound to obtain more information about the abnormality.

Because an EUS provides extremely precise images, it’s also useful for:

  • Staging cancers
  • Helping your doctor determine the best course of treatment for your specific case

For cancers of the esophagus, stomach, small bowel and rectum, an EUS may allow your doctor to see how deep the cancer is and whether or not it’s spread to nearby organs or lymph nodes. An EUS also may be helpful in determining whether other cancers, such as pancreatic or lung cancer, have spread in or near the bowel structures.

How to prepare for an endoscopic ultrasound

Your doctor will give you specific instructions before the EUS, so plan to follow them accordingly and ask any questions ahead of time. The steps you need to take to prepare depend on whether you’re having an upper or lower EUS.

With both procedures, it’s important that you discuss all prescription and over-the-counter medications you’re taking (as well as any vitamins or herbal supplements) with your doctor. If you have diabetes, bleeding or blood clotting problems, or any other major medical conditions, be sure to inform your doctor. Be sure to mention any symptoms you’re experiencing as well.

Upper EUS preparation:

  • No food after midnight on the night prior to your scheduled testing.
  • Avoid drinking water or other liquids in the three to six hours before your test; the exact amount of time will depend on the method of sedation being used.
  • Make plans to have someone drive you home after your test, and be prepared to rest for the remainder of the day.

Lower EUS preparation:

  • Your doctor will direct you on a bowel-cleansing preparation in advance of the procedure, which could be an enema or a more extensive protocol.
  • Stop eating foods and drinking liquids at the time(s) indicated by your doctor.
  • If you’re given pain medication during your EUS, you won’t be able to drive after the procedure, and you shouldn’t make important decisions. Plan to rest for the remainder of the day.

What to expect during an endoscopic ultrasound

Before your endoscopic ultrasound begins, you’ll be given an intravenous line to administer fluids, along with a medication to relax you and make you sleepy so that you won’t feel much during the procedure. Your care team will monitor your heart rate, blood pressure and pulse. Extra oxygen may be delivered through a nasal cannula if needed, and you’ll be asked to lie on your left side.

If you’re having an upper EUS, the back of your throat will be sprayed with a numbing agent, and the scope will be guided through your mouth and esophagus. A bite block may be put in place to safeguard your teeth as well as the endoscope. The scope will then travel into your stomach and duodenum (first part of small intestine) to provide images of your gastrointestinal tract. If needed, a fine-needle biopsy may be conducted using the ultrasound as a guide.

If you’re having a lower EUS, the endoscope will be inserted through your anus and into your colon so that the inside lining of your GI tract may be carefully examined. A fine-needle biopsy may be taken at this time.

After both procedures, you will return to an alert state as the medication wears off. You may experience a sore throat after an upper EUS or mild bloating or cramping with either procedure, but these should resolve within 24 hours. Your doctor will discuss your results with you at a follow-up appointment.

Endoscopic ultrasound benefits

Because an EUS occurs in real time, the images provide your doctor with much more detail than those from other imaging tests such as X-rays and CT scans. Additionally, there’s no exposure to radioactive substances or radiation, making an EUS a safer option. It also provides your doctor with the opportunity to collect a biopsy at the time of the procedure.

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