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Bowel cancer


Expert reviewer, Dr Alistair McNair, Consultant Gastroenterologist
Next review due October 2023

Bowel cancer is the name for any cancer that starts in your large bowel (colon) or back passage (rectum). Other names for bowel cancers include colon cancer, rectal cancer and colorectal cancer.

It’s one of the most common types of cancer in the UK; more than 40,000 people get bowel cancer each year.

About bowel cancer

In 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, that 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 your 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 why certain people get bowel cancer. But it’s thought that it probably happens because of a mixture of different factors.

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

  • have a family history of bowel cancer – you’re twice as 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 below for more information on this.

Other risk factors can include:


Having any of these risk factors doesn’t mean that you will definitely get bowel cancer – but they increase your chances of developing it. However, you can develop bowel cancer without having any of these risk factors.

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Symptoms of bowel cancer

Symptoms of bowel cancer can include the following.

  • Bleeding from your bottom or having blood in your poo. 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 fully emptied your bowel when you’ve 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.

Having these symptoms doesn’t necessarily mean that you have bowel cancer – they can also be symptoms of much less serious conditions. But if you have them, especially if they don’t go away and aren’t normal for you, contact your GP. You should always see your GP if you have blood in your poo.

Sometimes, bowel cancer can cause a blockage (obstruction) of your bowel. This can cause sudden cramping pains in your tummy, bloating, constipation and being sick. You should seek immediate medical attention if you develop these symptoms.

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

Diagnosis of bowel cancer

Your GP will ask about your symptoms and your medical history. It can be worth keeping a diary to keep track of your symptoms, which you can share with your GP. They’ll need to examine you, which will include 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 below: What happens during a rectal examination?

Your GP may also suggest you have a blood test to see if you have anaemia and to check your general health. They may ask you to provide a poo sample, to check for any hidden blood in your poo.

If your 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 (gastroenterologist) or a surgeon who specialises in diseases of the large bowel (colorectal surgeon).

Your specialist may suggest some of the following tests.

  • A colonoscopy. This allows 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 biopsy (small sample of tissue) 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 in some cases.
  • A virtual colonoscopy. This uses a CT scan to create a three-dimensional image of the inside of your bowel. This is an option 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 ultrasound, CT and MRI scans.

Screening for bowel cancer

If you're between the ages of 60 and 74, you’ll be offered bowel cancer screening every two years in England, Wales and Northern Ireland. In Scotland, it’s offered between the ages of 50 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, and 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 live in England, you may also be invited to a one-off sigmoidoscopy test, called bowel scope screening, after you turn 55. This isn’t available in all areas, and you’ll still be sent the FIT kit after you turn 60.

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

Treatment of bowel cancer

Your treatment and care will be managed by a team of doctors and other cancer specialists. They will discuss with you what treatments they recommend in your particular circumstances. 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 symptoms.

Surgery

If possible, your medical team will aim to remove the cancer with bowel surgery. This may be with 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 decide it’s best to give your bowel a chance to heal by forming a stoma. This is where the end of your bowel is brought out to the surface of your tummy. A bag called a colostomy 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 also have some of the following treatments as well as or instead of surgery.

  • Chemotherapy – this means taking 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, as well as 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 lifestyle measures you can take 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.

Screening for people at high risk of bowel cancer

If you’re at high risk of bowel cancer, your doctor may recommend regular screening tests to check for any cancerous changes in your bowel. This might be if you have a strong family history of bowel cancer or a particular health condition, like ulcerative colitis, that puts you at greater risk. If any polyps (growths of tissue) or areas of concern are spotted during your screening test, you may be able to have surgery to remove them and prevent cancer developing.

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

Frequently asked questions

  • During a rectal examination, your doctor will feel inside your rectum (back passage) with their finger. Although it may feel a little strange and uncomfortable, it doesn’t hurt and only takes a minute or two. You can ask for someone else to be present in the room during the examination if you wish.

    You’ll be asked to remove your lower clothing and lie on your left side on the couch, with your knees drawn up. Your GP will put a glove on one hand and lubricate their finger with a gel. They’ll gently slide one finger into your back passage. You may feel their finger moving around as they check for any lumps or abnormalities.

    It’s important not to put off seeing your GP about your symptoms because you’re worried about having a rectal examination. There’s no need to feel embarrassed – it’s an important medical test that your GP will have done many times before.

  • Yes, there’s an increased chance of getting bowel cancer if you have inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. These diseases cause long-term inflammation of your bowel. Over time, the damage caused to the lining of your bowel increases the risk of cancer developing. Your risk of getting bowel cancer increases the longer you have Crohn’s disease or ulcerative colitis. It also depends on how much of your bowel is affected.

    If you have Crohn's disease that affects your large bowel or ulcerative colitis, you should 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 and may vary between once a year and once every five years. Ask your doctor about your risk of bowel cancer and if you should be screened.



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  • Reviewed by Pippa Coulter, Freelance Health Editor, October 2020
    Expert reviewer, Dr Alistair McNair, Consultant Gastroenterologist
    Next review due October 2023

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