Further tests after diagnosis

If your biopsy shows that you have anal cancer, you will need to have further tests. This is to find out the size of the cancer and if it has spread anywhere else.

You will usually have a CT (computerised tomography) scan and an MRI (magnetic resonance imaging) scan. These scans build up a picture of the inside of your body. You may also have an anal ultrasound scan. This is to find out the size of the tumour and if it has spread.

If the lymph nodes in your groin are bigger than normal, the doctors may use a test to see if the cancer has spread to the lymph nodes. This is called a fine needle aspiration (FNA). It may be uncomfortable but it is very quick.

It can take up to two weeks to get your results. Waiting for these can be difficult. It can help to talk about your worries with someone close to you.

Further tests

If the biopsy shows you have anal cancer, you will need further tests. These are done to find out more about the position of the cancer and to see if it has spread.


CT (computerised tomography) scan

A CT scan takes a series of x-rays, which build up a three-dimensional picture of the inside of the body. The scan takes 10–30 minutes and is painless. It uses a small amount of radiation, which is very unlikely to harm you and will not harm anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.

CT scan
CT scan

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You may be given a drink or injection of a dye, which allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. It’s important to let your doctor know if you are allergic to iodine or have asthma, because you could have a more serious reaction to the injection.

You’ll probably be able to go home as soon as the scan is over.

Someone having a CT scan

Having a CT scan

A radiographer explains how a CT scan works, and Jyoti talks about her experience.

About our cancer information videos

Having a CT scan

A radiographer explains how a CT scan works, and Jyoti talks about her experience.

About our cancer information videos


MRI scan

This test uses magnetism to build up a detailed picture of areas of your body. The scanner is a powerful magnet so you may be asked to complete and sign a checklist to make sure it's safe for you. The checklist asks about any metal implants you may have, such as a pacemaker, surgical clips, bone pins, etc. You should also tell your doctor if you've ever worked with metal or in the metal industry as very tiny fragments of metal can sometimes lodge in the body. If you do have any metal in your body it's likely that you won't be able to have an MRI scan. In this situation another type of scan can be used.

Before the scan, you'll be asked to remove any metal belongings including jewellery. Some people are given an injection of dye into a vein in the arm, which doesn't usually cause discomfort. This is called a contrast medium and can help the images from the scan to show up more clearly. During the test you'll lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It's painless but can be slightly uncomfortable, and some people feel a bit claustrophobic. It's also noisy, but you'll be given earplugs or headphones. You can hear, and speak to, the person operating the scanner.


Anal ultrasound scan

This test uses sound-waves to form a picture. It isn’t used very often in diagnosing anal cancer.

A doctor passes a small probe that makes sound-waves into your back passage (rectum). It takes about 15 to 30 minutes. This can be uncomfortable, so let your doctor know if you have any pain.


Fine needle aspiration (FNA) of the lymph nodes

You may have this test if the lymph nodes in your groin are larger than normal. It is done to see if there are any cancer cells in the lymph nodes.

The doctor passes a fine needle into the lymph node and withdraws (aspirates) some cells into a syringe. This might feel a little uncomfortable, but it’s very quick. You might have an ultrasound scan at the same time to help guide the needle.

After the test, a doctor examines the sample under a microscope to check for cancer cells.


PET-CT scan

This is a combination of a CT scan, which takes a series of x-rays to build up a three-dimensional picture, and a positron emission tomography (PET) scan. A PET scan uses low-dose radiation to measure the activity of cells in different parts of the body.

PET-CT scans give more detailed information about the part of the body being scanned. You may have to travel to a specialist centre to have one. You can't eat for six hours before the scan, although you may be able to drink. A mildly radioactive substance is injected into a vein, usually in your arm. The radiation dose used is very small. The scan is done after at least an hour’s wait. It usually takes 30–90 minutes. You should be able to go home after the scan.


Waiting for test results

Waiting for test results can be a difficult time. It may take from a few days to a couple of weeks for the results of your tests to be ready. You may find it helpful to talk with your partner, family or a close friend. Your specialist nurse or one of the organisations listed on our database, can also provide support. You can also talk things over with one of our cancer support specialists on 0808 808 00 00.

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