What is bowel cancer?

Clinical Oncologist Katherine Aitkens explains bowel cancer, giving an overview of bowel cancer symptoms, diagnosis, and treatment.


The bowel is part of the digestive system and is divided into the small bowel and large bowel. The large bowel is made up of the colon, rectum and anus. The term bowel cancer is normally used to talk about:

The term bowel cancer can also be used when talking about other cancers, including:

If you are diagnosed with bowel cancer, it means you have one of the specific cancers listed above. If you are not sure which type, ask your GP, cancer doctor or specialist nurse for more information.

What is colorectal cancer?

The term colorectal cancer can also be used when talking about colon cancer and rectal cancer.

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Symptoms of bowel cancer

Some people may start by seeing their GP because they have symptoms.

Find out more about symptoms for different types of bowel cancer:

If you have any symptoms or notice anything that is unusual for you, you should see your GP straight away.

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Causes of bowel cancer

Doctors do not know the exact causes of bowel cancer. But there are risk factors that can increase your chance of developing it.

Different risk factors may increase the chance of being diagnosed with bowel cancer. Find out more about the causes and risk factors for different types of bowel cancer:

Diagnosis of bowel cancer

If you have symptoms, you will usually begin by seeing your GP, who will examine you. If they think that your symptoms could be caused by cancer, they will refer you to a specialist doctor.

The tests you are given will depend on the type of bowel cancer you may have. Tests may include:

  • Rectal examination

    A rectal examination is when the doctor places a gloved finger into your back passage to feel for any lumps or swelling.

  • Blood test

    You will usually have a blood test to check your level of red blood cells. If you have a low number of red blood cells, this is called anaemia.

  • Colonoscopy

    A colonoscopy looks at the inside of the whole length of the large bowel. You can usually have this test as an outpatient. It takes about an hour.

  • Virtual colonoscopy

    In a virtual colonoscopy, a computerised tomography (CT) scanner takes a series of x-rays. This builds up a three-dimensional picture of your bowel.

  • Sigmoidoscopy

    A sigmoidoscopy looks at the inside of the rectum and the part of the colon closest to the rectum (the sigmoid colon). You can usually have it as an outpatient.

  • Biopsy

    During a biospy, the doctor removes a small piece of tissue or a sample of cells to be checked for cancer.

There are other ways you may be diagnosed:

  • Having NHS Bowel Screening
    Bowel cancer screening is a way of finding bowel cancer at an early stage before it causes symptoms. If you have a family history of bowel cancer, you may need to have bowel screening at an earlier age.
  • Going to hospital with a problem, such as bowel obstruction
    This is when part of the bowel becomes blocked. It may cause symptoms such as tummy pain, nausea and vomiting, and constipation.


Booklets and resources

Staging and grading of bowel cancer

The results of your tests help your doctors find out more about the size and position of the cancer and whether it has spread. This is called staging.

A doctor decides the grade of the cancer by how the cancer cells look under the microscope. This gives an idea of how quickly the cancer might grow or spread.

Knowing the stage and grade helps your doctors plan the best treatment for you.

Find out more about the staging and grading for different types of bowel cancer:


Treatment for bowel cancer

A team of specialists will meet to discuss the best possible treatment for you. This is called a multidisciplinary team (MDT) for bowel cancer.

Your cancer doctor or specialist nurse will explain the different treatments and their side effects. They will also talk to you about things to consider when making treatment decisions.

The treatment you have will depend on which type of bowel cancer you have. It will also depend on your general health and preferences.

After bowel cancer treatment


After your treatment has finished, you will have regular check-ups, tests and scans. These appointments are a good opportunity to talk to your doctor about any worries or problems you have.

We have more information about follow-up care after treatment.

You may get anxious between appointments. This is natural. It may help to get support from family, friends or a support organisation. 

Macmillan is also here to support you. If you would like to talk, you can: 

Sex life

Bowel cancer and its treatment can affect your sex life. Changes may get better over time, but sometimes they are permanent. If you have any problems or are worried about this, talk to your doctor or nurse. They can explain what to expect and there are often things that can help.


Some cancer treatments can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

Well-being and recovery

Even if you already have a healthy lifestyle, you may choose to make some positive lifestyle changes after treatment.

Making small changes such as eating well and keeping active can improve your health and wellbeing and help your body recover.

Related pages

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We have information about bowel cancer in over 16 languages, and in other formats including audiobooks, and easy read.

If we don't have what you are looking for, you can ask for information to be translated for free or provided in a format to suit you. Email us at cancerinformationteam@macmillan.org.uk or call us on 0808 808 00 00.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 30 April 2020
Next review: 30 April 2023

This content is currently being reviewed. New information will be coming soon.

Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.