Tests for anal cancer

You might have a number of tests to check for anal cancer. The anus is the part of the bowel that opens to the outside of the body.

The tests you might have include:

  • an examination of your anus and rectum (back passage)
  • taking a sample of tissue from your anus called a biopsy
  • scans
  • taking a sample of tissue from the lymph nodes Open a glossary item in your groin. This is a fine needle aspiration (FNA)

Tests your GP might do

Most people with symptoms that could be due to cancer start by contacting their GP surgery. Your first appointment may be a telephone appointment. Your GP surgery then might arrange for you to go in and see a doctor or other healthcare professional.

The tests your GP might do include one or more of the following:

  • an examination of your anus and rectum
  • a test that looks for tiny traces of blood in a sample of poo. This is a Faecal Immunochemical Test (FIT)
  • blood tests

Your GP may also ask you for another sample of poo to check for inflammation in the bowel. This test is called Faecal Calprotectin. Your GP or practice nurse will give you a sample pot to take away with you. You then bring it back once you have collected the poo sample.

Examination of your anus and rectum

This examination involves your doctor feeling inside your anus and back passage using their gloved finger. This is also called a digital rectal exam (DRE). They look for any lumps or hard areas.

It’s normal to feel anxious about this test but it usually only takes a few minutes. You can ask for someone else to be in the room if you want, to act as a chaperone. This chaperone can be a friend or relative, or a health professional such as a practice nurse.

Testing for blood in your poo using FIT

FIT is a test that looks for blood in a sample of poo. It looks for tiny traces of blood that you might not be able to see which could be a sign of cancer.

Not everyone has this test. For example, your GP might refer you to a specialist doctor without doing a FIT if they see a lump or an abnormal looking wound (ulcer) in your anus.

Blood tests

Blood tests can check your general health, including how well your liver and kidneys are working. Your doctor can also check the number of blood cells Open a glossary item such as red blood cells. 

Tests your specialist might do

Depending on the results of your tests, your GP might refer you to a specialist. You are usually referred to a lower gastrointestinal (lower GI) clinic where you might see a GI specialist nurse or colorectal doctor.

Your specialist usually does more tests. These include:

  • an anal examination using a thin tube to look at the anus (anoscopy) and biopsy
  • MRI scan
  • CT scan
  • PET-CT scan
  • taking a sample of tissue from the lymph nodes in your groin. This is a fine needle aspiration (FNA)

Anal examination (anoscopy) and biopsy

Your doctor looks at the anus and the area around it using a thin tube called an anoscope. They might also look at the rectum using a slightly longer tube. This is a proctoscopy.

During this exam, your doctor might take samples of tissue from any abnormal area. This is a biopsy.

You usually have this test in the outpatient department using a local anaesthetic Open a glossary item. You may also have it in the operating theatre under a general anaesthetic Open a glossary item but this is rare.

MRI scan

MRI stands for magnetic resonance imaging. It uses magnetism and radio waves to take pictures of the inside of the body.

You might have an MRI scan of your pelvis. The pelvis is the area between your hip bones. Doctors use the MRI scan to find out:

  • where in the anus the cancer is
  • how big it is and whether it has spread anywhere else in your pelvis (the stage)
  • check how well the treatment is working

You may have an injection of a dye (contrast medium) before the scan to help make the pictures clearer.

CT scan

CT (or CAT) stands for computed (axial) tomography. It is a test that uses x-rays and a computer to create detailed pictures of the inside of your body.

You may have a CT scan of your chest, tummy (abdomen) and pelvis. This is to find out whether the cancer has spread to other parts of the body.

PET-CT scan

A PET-CT scan combines a CT scan and a PET scan. This type of scan can give detailed information about your cancer.

You might have a PET-CT scan to:

  • help decide the best treatment for your cancer
  • show how well treatment is working
  • check whether the cancer has come back

Checking for cancer cells in the lymph nodes in your groin

Anal cancer can sometimes spread into the lymph nodes in your groin. To check for this, you may have an ultrasound of the groin area.

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.

If any areas look abnormal, doctors can use the ultrasound to guide a needle and take a sample of cells (biopsy). This is called a fine needle aspiration (FNA).


The tests you have helps your doctor find out if you have anal cancer and how far it has grown. This is the stage of the cancer.

This is important because doctors recommend your treatment according to the stage of the cancer.

Coping with anal cancer

Coping with a diagnosis of anal cancer can be difficult. There is help and support available to you and your family.

  • Suspected cancer: recognition and referral
    National Institute for Health and Care Excellence (NICE), 2015. Last updated August 2023

  • Lower GI/Colorectal Cancer suspected
    NHS Clinical Pathways, Last accessed September 2023

  • Anal Cancer
    BMJ Best Practice, Last updated September 2023

  • Anal cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow up
    S Rao and others
    Annals of Oncology, 2021. Vol 32, Issue 9. Pages 1087-1100

  • Scottish referral guidelines for suspected cancer – Lower gastrointestinal cancer
    NHS Scotland, Last updated May 2023

  • Quantitative faecal immunochemical testing to guide colorectal cancer pathway referral in primary care
    National Institute for Health and Care Excellence (NICE), 2023

Last reviewed: 
07 Nov 2023
Next review due: 
07 Nov 2026

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