Endoscopic Ultrasound (EUS)

The endoscope (flexible tube) for endoscopic ultrasound (EUS) has a small ultrasound scanner at the tip. The test is commonly performed with sedation.

There are two kinds of EUS – radial and linear. A radial EUS is performed for diagnostic reason whereas a linear EUS may be done for both diagnostic and therapeutic reasons.

Common reasons for the test:

Radial EUS
1. to diagnose the stage of oesophageal (gullet) cancer
2. to look for sludge or minute stones (microlithiasis) in the bile ducts and gallbladder (biliary system)
3. to obtain detailed picture of an abnormality or abnormal area in the upper gastrointestinal (GI) tract or pancreas/biliary system, that may have been found by another test

Linear EUS
1. to obtain detailed picture of an abnormality and take some tissue or cyst fluid samples (biopsies or fine needle aspirate) in the upper GI tract or pancreas/biliary system, that may have been found by another test
2. to aspirate a pancreatic cyst or drain a pseudocyst (with a cyst-gastrostomy and stenting). The latter involves x-ray and is normally done in the radiology department


The EUS test complements other imaging tests such as computed tomography (CT), Positron emission tomography CT (PET-CT) or MRI scans to increase certainty of a correct diagnosis. It is sometimes possible for an abnormality in the upper GI tract/pancreas or pancreatic cyst to be sampled or drained via a needle puncture through the skin (percutaneous) or stomach wall respectively, without any EUS guidance. The disadvantages include an increased bleeding risk for smaller lesion(s) without the doppler function of EUS to help avoid any adjacent blood vessel, and potential for tumour seeding along the needle track.

Preparing for the test

Stop clopidogrel (7 days) or warfarin (5 days) before the test if instructed, and temporary heparin injection may be necessary

On the day of test

Fasting (nothing to eat) for 6 hours before the test
Small amounts of clear fluid or water are safe up to 2 hours before the test
Blood sugar (BM) is checked in patients with diabetes mellitus
A cannula (small plastic tube) is inserted into a vein

In the Endoscopy room

A monitoring probe is attached to a finger, and a nasal cannula attached to a nostril for oxygen supplementation
Denture (if present) is removed
Plastic mouth guard is applied
Endoscope is introduced into the mouth

Drugs commonly used for the test

Topical spray - Local anaesthetic throat spray
Injection - Sedatives (benzodiazepine, midazolam)
- Pain killer (morphine, commonly pethidine or fentanyl)

Patient position during the test

Left lateral (see picture 1)

Picture 1

Can I watch the test?

This is not feasible as the head position faces away from the video and/or x-ray (fluoroscopy) monitors and the moderate deep sedation administered during EUS.


You won’t feel any pain from having some biopsies taken or fine needle aspiration. There is no significant discomfort associated with the puncture/drainage of a pancreatic pseudocyst that involves an electrically heated wire (diathermy) passed through the endoscope.

Injection of additional sedative or painkiller (morphine) drugs will be given as necessary during the tests for adequate control of pain or discomfort.

Specific complications

In diagnostic EUS, the complications of perforation (tear of the linings of oesophagus, stomach or duodenum) or bleeding occur extremely infrequently (less than 1 in 1000 cases).

Endoscopic ultrasound to perform biopsies or fine needle aspiration of cyst slightly raises the risk of bleeding or infection. Antibiotics injection may be given to help reduce infection risk for cyst aspiration.

If there is any suspicion of the perforation or bleeding complication during or straight after the test (in recovery), patients will be admitted for close monitoring and/or treatment.