28.MAY.2019 5 MIN READ | 5 MIN READ

Advanced endoscopic procedures like Endoscopic Ultrasound (EUS) can pinpoint the exact cause of your symptoms for a more accurate diagnosis. In this article, we’ll take a closer look at EUS and what you can expect.

What is EUS?

Endoscopic ultrasound (EUS) is a minimally invasive procedure used to evaluate diseases in the abdomen and chest cavity. The EUS endoscope is a slim and flexible tube with a video camera and a scanning probe mounted at its end. The endoscope is inserted through your mouth or anus, into your digestive tract where it uses high frequency ultrasound waves to create a detailed image of your internal organ’s linings and walls.

EUS enables your doctor to sample fluid and tissue from your abdomen or chest through a procedure called ‘Fine Needle Aspiration’. A needle obtains cells from the area of interest and this material is sent to the laboratory, where it is analysed by a pathologist. This procedure is the preferred alternative to an open exploratory surgery, if the area of interest is accessible endoscopically.

Why do you need to go for EUS?

Why have an endoscopic ultrasound?
EUS can be used to determine the cause of your symptoms, such as abdominal pain. It is used to examine the bile duct for gallstones, pancreas and abnormal growths within the central chest and upper abdomen. Tissue can be obtained from enlarged lymph nodes and suspected tumours in the digestive tract and pancreas.

Your doctor is able to view your digestive organs in high resolution during an EUS examination, as its images are magnified. As EUS is performed within your body, its ultrasound waves can penetrate deeper than an ultrasound examination that is conducted from surface of your body.

EUS is useful in the diagnosis of diseases such as:

  • Bile duct stones
  • Cancers of the digestive system
  • Pancreatic cysts and tumours
  • Abnormal growths in the stomach, oesophagus, rectum (submucosal tumours, sub-epithelial lesions)
  • Lymphoma and enlarged lymph nodes in the abdomen and chest.

With the therapeutic capabilities of EUS, some treatments can be performed without having a wound on the skin. These treatments are:

  • Drainage of pancreatic cysts
  • Aspiration of fluid-filled collections in the abdomen
  • Applying nerve blocks for the treatment of pain from pancreatic disease
  • Treating the bleeding from a ruptured vessel in the digestive tract

Is EUS a painful procedure?

No. You will be given light sedation, so that you will not experience any discomfort during your procedure. As EUS is performed inside your digestive tract and there is no injury to your skin, you are not expected to experience pain.

If ‘Fine Needle Aspiration’ is performed, you may feel a little sore after it is completed. This sensation resolves within a day or two.

How to prepare for EUS

Preparing for an endoscopic ultrasound
Some of these instructions will be given to you before the procedure:

  • Your stomach must be empty. You are required to fast 6 hours before the EUS examination for your digestive tract to be ready.
  • If you are undergoing EUS from the rectum, you may be given a laxative to drink in order to clear your bowels.
  • If your doctor is performing EUS with a ‘Fine Needle Aspiration’ procedure, you may need to stop your blood thinning medicines for a few days before the procedure.
  • Plan your recovery ahead of time. Make arrangements for someone to accompany you home after the EUS procedure. You should refrain from driving immediately after discharge. Medical leave will be given for 1 – 2 days.

How is it done?

EUS is often performed as a day procedure. This means that you can go home on the same day, approximately 2 hours after it is completed.

You will be given sedation prior to the procedure. This allows you to relax and fall asleep while EUS is being performed.

After you are sedated, your doctor will start inserting the EUS endoscope into your mouth or rectum. With the endoscopy, your doctor will be able to observe your digestive tract or area of interest on a LCD screen and an ultrasound monitor.

For ‘Fine Needle Aspiration’ procedures, your doctor will insert a special device through the channel of the EUS endoscope. This device emerges from the tip of the endoscope into your digestive system. A slender needle from the device will targets the abnormal area, obtaining cells or fluid for analysis. A cytotechnologist may be present during your procedure, who will then mounts the cells onto glass slides, and examines it under a microscope. Once enough material is obtained, the samples are sent to the pathologist.

The endoscope is withdrawn at the end of the procedure, and you will wake up shortly after. The entire procedure takes about 40 minutes.

What kind of doctor can perform EUS?

Endoscopic ultrasound specialist
An EUS procedure requires a high degree of skill and expertise. Doctors who can perform this procedure are usually very experienced, and even then, only a handful of specialists are trained in this advanced technique. The EUS procedure requires sub-speciality training in advanced endoscopy techniques and advanced endoscopic equipment. Only specialists who have undergone training in EUS are able to interpret the ultrasound images.

If you undergo a ‘Fine Needle Aspiration’, the cells are sent to a pathologist who will publish a report on the abnormalities identified. Your doctor will refer to this report and inform you of your diagnosis and how to better treat your condition.


EUS is a safe procedure when conducted in a medical centre with a team of experienced healthcare professionals. Your doctor will go through the risks with you before the procedure. A ‘Fine Needle Aspiration’ procedure confers a slightly higher risk than the EUS procedure alone.

In general, the risks are small (1 – 2% for Fine Needle Aspiration procedure and less than 1% for EUS procedure) and they include:

  • Bleeding
  • Adverse reactions to the sedation administered
  • Infection or inflammation around the area of needle puncture
  • Injury to the lining of the digestive tract

The risks of EUS are low because it is not considered as an operation.


Article reviewed by Dr Eric Wee, gastroenterologist at Mount Elizabeth Novena Hospital


Endoscopic ultrasound. (n.d.) Retrieved from https://www.mayoclinic.org/tests-procedures/endoscopic-ultrasound/about/pac-20385171

Endoscopic Ultrasound. (2017, October 23) WebMD Medical Reference. Retrieved from https://www.webmd.com/digestive-disorders/endoscopic-ultrasound

Friedberg, S. R., & Lachter, J. (2017). Endoscopic ultrasound: Current roles and future directions. World journal of gastrointestinal endoscopy, 9(10), 499–505. doi:10.4253/wjge.v9.i10.499

Wee Wei Loong Eric
Mount Elizabeth Hospital

Dr Eric Wee is a gastroenterologist practising at Mount Elizabeth Novena Hospital, Singapore. He specialises in digestive and bowel problems such as gastric pain, reflux, bloating and irritable bowel syndrome, as well as pancreatic and liver diseases such as viral hepatitis, fatty liver and cirrhosis. He performs endoscopic therapy for inoperable gastrointestinal cancers.