Ultrasound of the anus

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 probe that gives off sound waves. The probe looks a bit like a microphone. The sound waves bounce off the organs inside your body, and the probe picks them up. The probe 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 might have it at one of the following:

  • your GP surgery
  • local community clinic
  • in your hospital x-ray department

A specialist healthcare professional called a sonographer usually does the test. 

Why you might have an ultrasound of your anus?

You might have an ultrasound scan to find out where the cancer is in your anus. It can also show the doctor how large your cancer is and how far it has grown. This helps your doctor decide about your treatment.

Preparing for your ultrasound

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. 

What happens?

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.

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.

After your ultrasound of the anus

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

Possible risks

Ultrasound scans are 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.

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