Bowel cancer

Your health expert: Dr Haney Youssef, Consultant Colorectal and Peritoneal Surgeon
Content editor review by Rachael Mayfield-Blake, May 2023
Next review due May 2026

Bowel cancer is cancer that starts in your large bowel (colon) or inside your back passage (rectum). Other names for bowel cancer include colon cancer, rectal cancer, and colorectal cancer. Bowel cancer is one of the most common types of cancer in the UK; more than 40,000 people get bowel cancer each year.

About bowel cancer

If you have bowel cancer, cells in your large bowel (colon) or back passage (rectum) start growing out of control. Most bowel cancers (around seven in 10) start in the colon, while around three in 10 start in the rectum. They usually develop from small, non-cancerous (benign) growths of tissue called polyps, which can become cancerous (malignant) over time.

Bowel cancer can spread through the wall of your bowel to the surrounding tissues, and to your lymph nodes nearby. It can also spread to other parts of your body, such as your liver and your lungs. The earlier bowel cancer is diagnosed, the better your chance of surviving it. So it’s important to see a GP if you have symptoms, and to consider screening tests if you’re offered them.

Image showing the large and small bowels

Causes of bowel cancer

It’s not known exactly what causes bowel cancer. It probably happens because of a mixture of different things.

Although you can develop bowel cancer at any age, it’s rare before 40. You’re more likely to get it as you get older. Your risk of developing bowel cancer is also higher if you:

  • have a family history of bowel cancer – you’re more likely to get it if your brother, sister, or one of your parents has it
  • have an inherited bowel condition, such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome
  • have a long-term bowel condition, such as Crohn's disease or ulcerative colitis 
  • have a history of non-cancerous growths (called polyps or adenomas) or previous cancers in your bowel

If you have any of these ‘risk factors’, your doctor may recommend you go for regular bowel cancer screening. See our prevention section for more information.

Other things that can increase your risk of bowel cancer include:

If you have any of these risk factors, it doesn’t mean you’ll definitely get bowel cancer – but they increase your chances of developing it. But you can develop bowel cancer without having any of them.

Symptoms of bowel cancer

An image showing the symptoms of bowel cancer
An image showing the symptoms of bowel cancer
An image showing the symptoms of bowel cancer
An image showing the symptoms of bowel cancer

People don’t always get bowel cancer symptoms in the earlier stages. If you do, symptoms of bowel cancer can include the following.

  • Bleeding from your bottom or blood in your poo may be one of the first signs of bowel cancer. The blood can be bright or dark red on the surface or mixed in with the poo. Or you may notice it in the toilet bowl. Occasionally it can make your poo look black, like tar.
  • Changes in your bowel habits. Your poo may be looser (diarrhoea) or you may find it harder to go (constipation). You may feel like you need to go more often or more urgently or you might feel like you haven’t finished even when you’ve just been.
  • You might feel extremely tired and weak (fatigued). This can be due to anaemia, which means you have a lower than normal level of red blood cells.
  • Pain or discomfort in your tummy (abdomen) or back passage that doesn’t go away.
  • Losing weight, when you haven’t been trying.

If you have these symptoms, it doesn’t necessarily mean that you have bowel cancer – they can also be symptoms of much less serious conditions. These include conditions such as irritable bowel syndrome. But if you have them, especially if they don’t go away and aren’t normal for you, contact a GP. Talk to a GP if you’re worried about blood in your poo too.

Sometimes, bowel cancer can cause a blockage (bowel obstruction). This can cause:

  • sudden cramping pains in your tummy
  • bloating
  • constipation
  • being sick

Seek immediate medical attention if you get these symptoms.

Diagnosis of bowel cancer

A GP will ask about your symptoms and your medical history. It may help to keep a diary to track your symptoms, which you can share with the GP. The GP will examine you by feeling around your tummy and inside your back passage (rectum) to check for any signs of lumps or swellings. For more information on this, see our FAQ: What happens during a rectal examination?

The GP may give you a blood test to see if you have other health conditions, such as anaemia. The blood test will check your general health too. They may ask you to provide a poo sample, to check for any hidden blood in your poo.

If the GP thinks your symptoms need further investigation, they’ll refer you to a specialist. This may be a medical consultant who specialises in bowel conditions (colorectal specialist). Your specialist may suggest some of the following tests.

  • A colonoscopy. This will allow your doctor to look at the lining of your large bowel using a narrow, flexible, tube-like telescopic camera called a colonoscope. Your doctor can also use this to take a small sample of tissue (biopsy), which they’ll send to a lab to look for cancer cells. 
  • A sigmoidoscopy. This is similar to a colonoscopy, but just looks at the inside of your back passage and the lower part of your bowel. Your doctor may suggest it as an alternative to colonoscopy. 
  • A virtual colonoscopy. This uses a CT scan to create a three-dimensional image of the inside of your bowel. This option is offered in some areas if you aren’t well enough to have a colonoscopy. It’s also known as CT colonography. 

If these tests find you have bowel cancer, you’ll need further tests to find the size and position of the cancer, and to check if it has spread. This is called staging and may include CT and MRI scans.

Screening for bowel cancer

If you’re registered with a GP surgery, they’ll invite you for bowel cancer screening every two years. When you’re invited for screening depends on where you live.

  • In England, if you're between 60 and 74, you’ll be offered bowel cancer screening, and in some areas, from the age of 50.
  • In Northern Ireland, if you’re between 60 and 74 you’ll be invited for screening.
  • In Scotland, it’s offered between 50 and 74.
  • In Wales it’s offered between the ages of 55 and 74.

You can also request a test if you're over 74. Screening is important because it may detect bowel cancer before you have symptoms. This is when treatment is likely to be more effective.

The screening kit, called the faecal immunochemical test (FIT), is sent to you to do at home. The test can detect small amounts of blood in your poo that you may not normally notice. It doesn't diagnose bowel cancer – but the results will show whether or not you need to have any further tests. If you have an abnormal screening result, you’ll be offered a colonoscopy.

While bowel cancer screening can help to detect cancer, it isn’t perfect and might not always pick it up. So it’s important to look out for symptoms, even if you’ve had a clear screening result.

Your GP surgery will have information about the bowel cancer screening programme in your area.

Looking for cancer cover that supports you every step of the way?

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To get a quote or to make an enquiry, call us on 0808 273 6216

Treatment of bowel cancer

Your treatment for bowel cancer and care will be managed by a team of doctors and other cancer specialists. They’ll discuss what treatment for bowel cancer they recommend for you. This will depend on the size of your tumour (lump of cells), its position and if it has spread, as well as your general health and fitness.

If you find out you have bowel cancer early on, it may be possible to cure it. If you’re diagnosed later and the cancer has spread, the focus of treatment may be on prolonging your life and reducing your symptoms.


If possible, your medical team will aim to remove the cancer with bowel surgery. This may be keyhole (laparoscopic) surgery, which means the surgeon will insert tiny instruments into several small cuts in your tummy, to perform the surgery. Or you may need to have open surgery, where your surgeon will make one large cut in your tummy.

Your surgeon will remove the affected part of your large bowel and, if possible, join the two open ends together. Sometimes they may form a stoma to give your bowel a chance to heal. This is where the end of your bowel is brought out to the surface of your tummy. A stoma bag is placed over the stoma to collect the waste from your bowel.

A stoma is usually temporary and can be reversed a few months later in another operation. But sometimes, if a lot of your bowel has been removed, a permanent stoma may be necessary. Most people won’t need this, but your surgeon will be able to let you know how likely it is for you. If you do need a stoma, a nurse will visit you after your operation to discuss with you how to care for your stoma.

Non-surgical treatments

You may have some of the following treatments as well as, or instead of, surgery.

  • Chemotherapy – this uses medicines to kill cancer cells. You might have this before surgery to shrink the tumour (lump of cells) or after surgery to reduce the chance of the cancer coming back. If you’re not able to have surgery, you may have chemotherapy to help slow down the growth of cancer and reduce your symptoms.
  • Radiotherapy – this uses radiation to destroy the cancer cells. You might have this if your cancer is in your rectum, alongside surgery and other treatments.
  • Targeted cancer drugs – these are medicines that can seek out cancer cells and interfere with the way they grow. They’re sometimes used alongside chemotherapy for bowel cancer, especially if the cancer has spread to other parts of your body.

Prevention of bowel cancer

It’s not always possible to prevent bowel cancer. But there are certain changes you can make to your lifestyle to help keep your risk as low as possible.

  • Keep to a healthy weight.
  • Eat a healthy, balanced diet with plenty of fruit and vegetables, high-fibre foods, and low amounts of processed and red meat.
  • Try to keep active by doing regular exercise.
  • If you smoke, try to stop. Speak to your GP for advice and support on stopping smoking.
  • Only drink alcohol in moderation – drink sensibly by keeping to recommended limits.

If you have a condition called Lynch syndrome, your doctor may recommend you take aspirin every day to help prevent bowel cancer. Ask your doctor for more information.

Screening for people at high risk of bowel cancer

If you’re at high risk of bowel cancer, you may need regular screening tests to check for any cancerous changes in your bowel. You’re at greater risk if, for example, you have a strong family history of bowel cancer or a particular health condition such as ulcerative colitis. If any polyps (growths of tissue) or areas of concern are spotted during your screening test, they may be removed to prevent cancer developing. Colon polyps can be removed with a procedure called a colonoscopy. Larger polyps may need to be removed by surgery.

If you think you may have an increased risk of getting bowel cancer, ask a GP about screening.

During a rectal examination, your doctor will put on some gloves and feel inside your back passage (rectum) with their finger. They’ll use lubricating gel. You may feel their finger moving around as they check for any lumps or abnormalities. This may feel uncomfortable but it shouldn’t hurt and only takes around 10 seconds. There’s no need to feel embarrassed – it’s an important medical test that your doctor has done many times before.

See our section on diagnosis of bowel cancer for more information.

Yes, bowel cancer is more likely if you have an inflammatory bowel disease such as Crohn’s disease or ulcerative colitis. You’ll be offered regular bowel cancer screening, from around 10 years after you first developed symptoms. How often you’re tested will depend on your risk – it may vary between once a year and once every five years.

See our section on causes of bowel cancer for more information.

Bowel cancer is most common in older people. Although you can develop bowel cancer at any age, it’s rare before 40. More than 40 out of 100 people diagnosed with bowel cancer in the UK are 75 or older.

See our section on causes of bowel cancer for more information.

Bowel cancer is likely caused by a mixture of different things. These include things like having a family history of bowel cancer or an inherited bowel condition such as Lynch syndrome that increases your risk. Your lifestyle can also affect your chances of getting bowel cancer. Things like your diet – if you don’t eat enough fibre and eat a lot of processed and red meats, it may increase your risk. It’s also important to do plenty of exercise and not smoke.

See our section on causes of bowel cancer for more information.

The main symptoms of bowel cancer include bleeding from your bottom or blood in your poo, and changes in your bowel habits. You might feel extremely tired and weak and pain or discomfort in your tummy or bottom that doesn’t go away.

See our section on symptoms of bowel cancer for more information.

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