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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 are completely painless. 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 radiographer moves a probe over your skin
  • internal ultrasound scan - when the doctor or radiographer inserts a probe into your body e.g. into your vagina or back passage
  • endoscopic ultrasound scan - this is when you have a thin flexible tube (endoscope) into your body to go further

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 outer 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.

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

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.

Diagram showing an ultrasound scan

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 radiographer 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 sonographer will ask you to empty your bladder before they start.

You may be asked to change into a hospital gown or asked to get dressed from the waist down. And you will have a sheet to cover you.

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

Before the scan

The doctor or sonographer will ask you to lie on your back with your knees bent and legs apart (as if you were having a cervical screening test or an internal examination). If this position is difficult for you, you may be able to lie on your side with your knees drawn up to your chest. 

You may not have this test if you have never had an internal examination or are a virgin. Contact the scanning department if you have any questions about this.  

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

Ultrasound scans are a very safe procedure. It doesn’t involve radiation and there are usually no side effects.

Getting your results

You should get your results within 1 or 2 weeks at a follow up appointment.

Waiting for test results can be a worrying time. You can contact your specialist nurse if you’re finding it hard to cope. It can also 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, IB Wilkinson, A Baldwin and E Wallin
    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. If you need additional references for this information please contact patientinformation@cancer.org.uk with details of the particular risk or cause you are interested in.

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