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Ultrasound scan

An ultrasound scan is a procedure that uses high frequency sound waves to create a picture of a part of the inside of your body.

The ultrasound scanner has a microphone that gives off sound waves. The sound waves bounce off the organs inside your body, and the microphone picks them up. The microphone links to a computer that turns the sound waves into a picture on the screen.

Ultrasound scans aren't painful but can cause some discomfort. You usually have them in the hospital x-ray department by a sonographer. 

Why you might have this test

Ultrasound scans can help doctors:

  • diagnose conditions including a number of different types of cancer
  • guide doctors when they need to take a tissue sample (biopsies)

Types of ultrasound scans

There are different types of ultrasound scans. The type you need depends on the area of your body you're having scanned. They include:

  • external ultrasound scan - when the doctor or sonographer moves a probe over your skin
  • internal ultrasound scan - when the doctor or sonographer inserts a probe into your body eg into your vagina or back passage
  • endoscopic ultrasound scan - your doctor uses a thin flexible tube (endoscope) to look at part of your body, such as your food pipe (oesophagus), and the area around it

External ultrasound scans

Preparing for your scan

Check your appointment letter for any instructions about how to prepare for your scan.

You might need to stop eating for 6 hours beforehand. Let the scan team know if this will be a problem for any reason, for example if you are diabetic.

They might ask you to drink plenty before your scan so that you have a comfortably full bladder.

Take your medicines as normal unless your doctor tells you otherwise.

Before the scan

When you arrive at the clinic a member of staff might ask you to take off your clothing down to your underwear and put on a hospital gown. It will depend on what part of the body you're having scanned as to whether you have to undress or not. 

During the scan

You lie on the couch next to the ultrasound machine. You might be able to sit up depending on which part of your body is being scanned.

The sonographer will spread a clear gel onto your skin over the area they are checking. The gel feels cold. It helps to transmit the sound waves to the microphone. The scan appears on a screen next to you. 

You might feel a little pressure as the sonographer presses the microphone against your skin and moves it around the area being scanned. Tell them if this is uncomfortable. 

An ultrasound scan can take up to 45 minutes depending on what's being scanned.

Photograph of man having ultrasound

What happens afterwards

You can eat and drink normally after the test. You can go straight home or back to work afterwards.

Internal ultrasound scans

Sometimes, doctors need to put the ultrasound microphone or probe inside your body to get a clearer picture. Most often this is done for a scan of your prostate or vagina.

Rectal ultrasound

You have this scan to check your prostate gland. This is called a transrectal ultrasound or TRUS.

Preparation for the scan

You'll be given written instructions on how to prepare for the ultrasound scan.

You usually need to make sure you have had a bowel movement beforehand so your back passage (rectum) is empty when you come for your appointment. You might need to have an enema to empty your bowel. 

An enema is a liquid that you put into your back passage. Or you might have a liquid medicine (laxative) to swallow the day before. You need to stay close to a toilet for a few hours after taking the medicine.

If you’re having some tissue taken (biopsy) at the same time you’ll have additional instructions and medication to take. 

The sonographer will ask you to change into a hospital gown or undress from the waist down. You’ll have a sheet to cover you.

Before the scan

You go into the scanning room which is slightly darkened, this helps the sonographer when looking at the screen. 

The doctor or sonographer will usually ask you to lie on your left side with your knees pulled up towards your chest. Or they may ask you to lie on your back with your legs spread apart and in stirrups.

During the scan

A small thin ultrasound microphone or probe is put into your back passage. It’s about the width of a thumb. The microphone or probe is covered with a protective sheath like a condom and has some lubricating gel on it.  

This test is uncomfortable and it may feel cool from the gel, but shouldn't hurt. You may feel vibrations from the machine from the probe.

This scan doesn’t take long.

Vaginal ultrasound

You might have a vaginal ultrasound to look at the ovaries, womb and surrounding structures. It is called transvaginal ultrasound or TVS.

Preparation for the scan

There is no special preparation needed for this scan. So you can eat and drink normally. And you can take your medications as normal.

The doctor or sonographer will ask you to empty your bladder before you have the scan. They may ask you to change into a hospital gown or undress from the waist down. You will have a sheet to cover you.

Before the scan

The doctor or sonographer asks you to lie on your back with your bottom at the end of a short scanning couch. There are supports for your feet so you can bend your knees and have your legs apart. If this position is difficult for you, you may be able to lie on your side with your knees drawn up to your chest.   

During the scan

The doctor puts a small thin ultrasound microphone or probe into your vagina. This looks like the same shape and size as a tampon. The probe is covered with a protective sheath like a condom and has some lubricating gel on it. The test may be uncomfortable and a little cool from the gel, but shouldn't hurt. This type of scan does not take long.

The sonographer will gently move the microphone or probe to get the pictures they need. At times the sonographer may place their hand on your tummy and press to move some of your organs to get a clear view on the screen.

Endoscopic ultrasound

This is a combination of having an endoscopy and an ultrasound. 

An endoscope is a long flexible tube with a light and camera attached. Doctors usually use it to look at the inside of your digestive system. The endoscope can also have an ultrasound probe at the tip. This gives doctors more detailed information. 

Doctors use endoscopic ultrasound to look at:

  • the wall of the oesophagus (food pipe)
  • the wall of the stomach
  • part of the small bowel (duodenum)
  • the gallbladder and bile ducts

This test can also look at the lymph nodes in your chest and abdomen.

Possible risks

An ultrasound scan is a very safe procedure. It doesn’t involve radiation and there are usually no side effects.

Getting your results

Your scan will be looked at by a specialist doctor and you should get your results within 1 or 2 weeks. You won't get any results at the time of the scan. 

Waiting for test results can make you anxious. Ask your doctor or nurse how long it will take to get them. Contact them if you haven’t heard anything after a couple of weeks.

You might have the contact details for a specialist nurse. You can contact them for information and support if you need to. It may help to talk to a close friend or relative about how you feel. 

For support and information, you can call the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday.

Contact the doctor that arranged the test if you haven't heard anything after a couple of weeks.

More information

We have more information on tests, treatment and support if you have been diagnosed with cancer.

Last reviewed: 
18 Dec 2018
  • Oxford handbook of clinical medicine (10th edition)
    M Longmore and others
    Oxford University Press, 2017

  • Transrectal ultrasound and prostate biopsy: Guidelines and recommendations for training.
    The British Association of Urological Surgeons and British Association of Urological Nurses, 2015

  • Evidence-based Guidelines for Best Practice in Health Care. Transrectal Ultrasound Guided Biopsy of the prostate
    European Association of Urology Nurses, 2011

  • How to perform transrectal ultrasound and prostate biopsy
    B Turner and L Drudge-Coates
    Nursing Standard, 2016. Volume 30, Issue 32, Pages 36 – 39

  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2015

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact with details of the particular issue you are interested in if you need additional references for this information.