Endoscopic Ultrasound (EUS)

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Cropped photo of a man in white coat and rubber gloves standing with a modern endoscope

What is a EUS?

An Endoscopic Ultrasound (EUS) is a minimally invasive procedure used to assess the digestive tract, including the lining of your upper (oesophagus, stomach and duodenum) and lower (colon and rectum) gastrointestinal tract. It also allows the gastroenterologist to examine structures next to the GI tract such as lymph nodes, tumours, collections, the pancreas, liver, gallbladder and bile duct. 

During this procedure, the gastroenterologist will insert a flexible, hollow tube called an endoscope either down your mouth or anus and down into your digestive tract. Patients are typically given sedation so they do not feel any pain during the procedure. 

The endoscope used in EUS is equipped with a video camera and an ultrasound scanning probe at its end. The video camera allows doctors to have a direct image of your digestive tract while the ultrasound probe uses high-frequency sound waves to produce detailed images of the linings of your digestive tract, as well as nearby organs. Because EUS is performed inside the body, the ultrasound waves can penetrate deeper than an ultrasound examination conducted from the body’s surface. 

Endoscopic Ultrasound Fine-needle aspiration (FNA) biopsy

During the EUS, another procedure called a fine-needle aspiration (FNA) might also be performed. FNA involves the use of a small, thin needle, and it is used to remove small tissue samples (biopsy) from your abdomen for analysis. 

Once the EUS is over, the FNA sample will then be sent to a lab to be examined by a pathologist, who is a doctor trained and specialised in interpreting and examining body tissues. Any abnormalities will be identified, and your gastroenterologist will refer to this report to help better inform you of your diagnosis, as well as discern further steps to be taken with regards to your treatment plan. 

EUS combined with FNA provides an overall minimally invasive alternative compared to exploratory abdominal surgery. It can be used for both diagnostic and therapeutic purposes. 

While EUS is generally safe and side effects are minimal, there may still be some risks involved. These include but are not limited to: 

  • Pain 
  • Bleeding 
  • Infection
  • Adverse reaction to sedation administered
  • Injury to nearby structures and organs  
  • Bowel perforation
  • Pancreatitis, if FNA of the pancreas is done

When would I need an EUS?

EUS can be either for diagnostic purposes or therapeutic purposes. They are used to address and treat a wide range of abdominal conditions. 

Indications for EUS include, but are not limited to: 

Diagnostic purposes 

EUS can be used to diagnose diseases, including:

  • Bile duct stones
  • Pancreatic cysts 
  • Any form of cancer in the digestive tract (oesophagus, stomach, rectum, pancreas)
  • Any abnormal growths in the digestive tract (stomach, oesophagus, rectum)
  • Lymphoma and enlarged lymph nodes in the abdomen and chest 

During the EUS, tissue can also be obtained via FNA (biopsy) for a more detailed analysis to aid in diagnosis. 

Therapeutic purposes

EUS can be used to treat certain medical conditions without the need to make a cut on the body and perform surgery. These include:

  • Drainage of pancreatic cysts
  • Aspiration of fluid-filled spaces in the abdomen
  • Treating any bleeding in the digestive tract from a burst blood vessel
  • For treatment of pancreatic diseases, via applying nerve blocks
  • Various ablative therapies

Why is an EUS important?

An EUS is a useful diagnostic procedure that allows your gastroenterologist to detect any structural abnormalities in the upper gastrointestinal tract. It is also used for minimally invasive therapeutic treatment for various abdominal conditions. 

In Dr Benjamin Yip’s personal opinion, the EUS is a procedure tailor-made for the pancreas, which is a deep-seated abdominal organ. It is located behind the stomach in the upper left abdomen, and is surrounded by many organs and structures such as the small intestine, liver and spleen. 

For both diagnostic or therapeutic purposes, an EUS allows the gastroenterologist to access the pancreas (given the configuration of the stomach and duodenum) in a minimally invasive manner. Otherwise, access to the pancreas would generally be performed percutaneously (via the skin), which would often not be possible due to the inaccessibility of the pancreas. 

How do I prepare for an EUS?

Before your EUS, you will be given certain specific instructions to help yourself prepare for the procedure. It is important to follow these instructions carefully.

In general, these instructions include: 

  1. Fasting before EUS - patients are usually required to fast ≥ 6h before the procedure.
  2. Bowel preparation (if EUS is done in the rectal area) - you may be asked to take a laxative/enema beforehand and to follow a liquid diet a day or two before the procedure. This will help to clear the bowel before the procedure so that a clear, clean and detailed view can be obtained.
  3. To stop taking certain medications - these include blood thinners, which can increase the risk of bleeding during EUS, especially if an FNA is being performed. Your doctor will further discuss your medication regime for the few days before the EUS with you, as this is very patient dependent.
  4. Plan ahead before your discharge - make arrangements to have someone accompany you home after the procedure. As sedation is used in EUS to help relax patients and minimise discomfort, you should refrain from driving immediately after discharge as the effects of sedative medications tend to last for several hours post-EUS. Some medical leave will be given. 

What can I expect for my EUS procedure?

Regardless of the indications for the procedure, the process of EUS remains largely the same. It is performed as a day procedure and patients can typically go home on the same day, around 2 hours after it is completed.

Prior to the procedure, sedation will be administered to help relax patients and minimise discomfort during the procedure. It is usually safe and will help you fall asleep. As EUS is performed inside your digestive tract, there will be no injury to the skin.

Once sedated, the EUS endoscope will be passed through your mouth or rectum, and the doctor will then observe the inside of your digestive tract through a standard monitor and an ultrasound monitor by the bedside.

If FNA is done, a small, thin needle will be inserted through the EUS endoscope and will emerge from the tip of the endoscope. Small tissue samples will be removed from your gut lining and will be sent to a laboratory for a pathologist to examine. 

At the end of the procedure, the endoscope will be withdrawn from the body, and you will be woken up shortly after that. In all, the EUS procedure tends to take around 60 minutes.

The endoscope is withdrawn at the end of the procedure, and you will wake up shortly after. 

Is EUS a painful procedure?

As you will be put under sedation, you generally will not be expected to feel any pain. However, you may feel slight discomfort when you first swallow the endoscope. If general anaesthesia (GA) is administered, you will be asleep throughout the entire procedure. 



After the procedure, you will be taken to a recovery room where you can rest and slowly wake up from the sedation. During this period, your vital signs will be continuously monitored, and adequate care will be rendered to you. 

Your doctor or primary care team might also come to check up on you and may explain any findings found during the EUS and FNA procedure. 

Recovery time usually takes around 1 hour. You will then be discharged with certain medications, care instructions, and any follow-up care plans will also be discussed. Make sure you arrange for someone you trust to accompany you home during this period, as you should refrain from driving. 

What do I eat after EUS?

  • Generally, you are allowed to resume your usual diet 2 hours after the procedure. You’re also encouraged to avoid alcohol at least 24 hours after your procedure.
  • If you experience a slight sore throat post-procedure, you can take warm liquids, throat lozenges or prescribed painkillers to ease the discomfort. 

Side effects and complications

If FNA is performed during the EUS, you might feel some slight soreness in your abdomen, but this will usually resolve within 1-2 days. Overall, EUS is a fairly safe procedure, and side effects should be minimal. You can reduce the risk of complications by carefully following the instructions given to you by your medical care teams.

Some warning signs to look out for include:

  • Severe and persistent abdominal pain
  • Black stools or bloody stools
  • Fever
  • Chest pain

Should you experience any of the above symptoms, please seek medical attention immediately. 


Overall, EUS is a minimally invasive and safe procedure that allows for both diagnostic testing and therapeutic treatment for various abdominal conditions. It is a safe alternative to surgery and it allows for a wide breadth of medical care and treatment. 

Dr Benjamin Yip believes that interventional EUS is one of the fastest moving areas in advanced endoscopy — “With the advent of various lumen apposing metal stents (LAMS), new minimally invasive procedures are being added to the repertoire of the advanced endoscopist. Many of these procedures can only be achieved with surgery in the past!”


  1. ASGE | Endoscopic Ultrasound (EUS), Fine Needle Aspiration (FNA), https://www.asge.org/home/about-asge/newsroom/media-backgrounders-detail/endoscopic-ultrasound-(eus)-and-fine-needle-aspiration-(fna). Accessed 7 May 2022.
  2. "Durability and long-term outcomes of direct EUS-guided gastroenterostomy using lumen-apposing metal stents for gastric outlet obstruction."PubMed, https://pubmed.ncbi.nlm.nih.gov/30705945/. Accessed 7 May 2022.
  3. “Endoscopic ultrasound.” Mayo Clinic, 29 May 2020, https://www.mayoclinic.org/tests-procedures/endoscopic-ultrasound/about/pac-20385171. Accessed 7 May 2022.
  4. “Endoscopic Ultrasound (EUS) | Johns Hopkins Division of Gastroenterology and Hepatology.” Johns Hopkins Medicine, https://www.hopkinsmedicine.org/gastroenterology_hepatology/clinical_services/advanced_endoscopy/endoscopic_ultrasound.html. Accessed 7 May 2022.
  5. McAlpin, John. What Can I Eat After an GI Upper Endoscopy (EGD)?, 14 March 2019, https://www.dhcoftx.com/blog/what-can-i-eat-after-an-upper-endoscopy-egd/. Accessed 7 May 2022.
    “Pancreas: What Is It, Function & Location.” Cleveland Clinic, 25 August 2021, https://my.clevelandclinic.org/health/body/21743-pancreas. Accessed 7 May 2022.

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Dr Benjamin Yip

Consultant Gastroenterologist
MBBS (Singapore), MRCP (UK), MCI (NUS), FRCP (Edin), FASGE (USA), FAMS (Gastroenterology)

Dr Benjamin Yip is a Consultant Gastroenterologist and the Medical Director of the Alpha Digestive & Liver Centre.

Dr Yip believes that gastrointestinal health is hugely interconnected to our whole-body health and sees patients with General Medical, as well as Gastroenterology and Hepatology problems.

His expertise lies in Advanced Endoscopy, including complex endoscopic procedures such as ERCP, EUS, single balloon enteroscopy, Spyglass cholangioscopy and enteral dilation/stenting.

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