Endoscopic Ultrasound (EUS): Uses, Preparation, and What to Expect

Endoscopic ultrasound (EUS) uses an endoscope (a thin, flexible tube with a camera) that has a small ultrasound probe on its tip. Because the probe sits right next to the organs being examined, EUS gives very detailed images of the digestive tract wall and nearby organs, such as the pancreas, bile ducts, gallbladder, liver, and lymph nodes. It can also guide a thin needle to take biopsies.

Where to have an EUS: None of our doctors perform EUS. We recommend seeing Dr. Patrick Chang at the Unio Specialty Care Pasadena office.

Why EUS is done

• Pancreatic cysts and masses, including sampling cyst fluid
• Cancer staging: measuring how deep a tumor goes and whether it has reached nearby lymph nodes, for cancers of the esophagus, stomach, pancreas, and rectum
• Growths in the wall of the GI tract (subepithelial lesions): showing which layer they come from and taking a biopsy
• Bile duct stones, often before deciding on ERCP
• Chronic pancreatitis and unexplained pancreatitis (see gallstones and pancreatitis)
• Fecal incontinence: checking the anal sphincter muscles
• Treatment in some cases, such as draining fluid collections or nerve blocks for pancreatic pain

How to prepare

Ask whether you are having an upper or lower EUS.

• Tell your doctor about all medicines (especially blood thinners, diabetes medicines, and weight-loss injections such as semaglutide or tirzepatide), allergies, and health conditions.
• Arrange for an adult to drive you home after sedation.
• Upper EUS: no solid food after midnight, and no liquids for up to 6 hours before, or as instructed.
• Lower EUS: an enema or a full colonoscopy-type bowel prep, as instructed.

What to expect during the procedure

EUS is done at an outpatient endoscopy center or hospital. For an upper EUS, you receive sedation, and the scope is passed through your mouth into the esophagus, stomach, and duodenum while you lie on your left side. The doctor views the camera and ultrasound images together and may take a sample with a thin needle (fine-needle aspiration or biopsy). The procedure usually takes 30 to 60 minutes. A lower EUS of the rectum is shorter and may need little or no sedation.

After the procedure

• A doctor or nurse will review the results with you and tell you when you can eat.
• You may have a mild sore throat, bloating, or cramps for up to 24 hours.
• Do not drive for the rest of the day. Plan to resume normal activities the next day.
• Biopsy results usually take several days.

Risks

EUS is very safe, with complications in less than 1% of patients. They include reactions to sedation, bleeding after a biopsy, infection (antibiotics may be given when cysts are sampled), pancreatitis after a pancreas biopsy, and rarely a tear (perforation). Like any test, EUS can occasionally miss an abnormality, so report new or ongoing symptoms and keep your follow-up.

Call your doctor right away for worsening belly pain, fever, vomiting, black stools, or bleeding after the procedure.

Make an appointment

Our gastroenterologists in Temple City care for patients from Arcadia, San Gabriel, Pasadena, Monrovia, Monterey Park, and across the San Gabriel Valley. We accept most PPO plans (see accepted insurances), and our doctors speak English, Vietnamese, and Mandarin. Schedule an appointment or call 626-898-4560.

This article is for general education and is not a substitute for medical advice. Talk with your doctor about your own health.