What Is Bowel Cancer? A Comprehensive Guide

Find out about the risk factors and symptoms of bowel cancer and when to get tested

Bowel cancer is a very serious disease affecting approximately 43,000 people in the UK every year. It’s the fourth most common cancer in the UK and the second biggest cancer killer.

As with any type of cancer, the earlier bowel cancer is diagnosed, the better the chances of survival.

This guide looks at what bowel cancer is, the risk factors, common symptoms, how it’s diagnosed, and more — so that you know how and when to get tested for bowel cancer in order to best protect your health.

What is bowel cancer?

The bowel makes up part of the digestive system and consists of two sections — the large bowel (colon, rectum and anus) and the small bowel (small intestine).

The bowel is responsible for processing all the food you eat, breaking it down into nutrients for the body to use. Once digestion has taken place, the bowel gets rid of any solid waste matter in the form of stool (poo).

Bowel cancer, also called colon or rectal cancer, is cancer that starts in the large bowel. It develops when cells in the bowel begin to divide and grow in an abnormal way. When abnormal cells get into surrounding tissues or organs, they create cancer. Over time, these cells can spread, causing cancer to grow in areas other than the bowel.

What causes bowel cancer?

The exact cause of bowel cancer is unknown, but research has shown that the risk of developing bowel cancer can be influenced by a number of factors.

Understanding these risk factors can help you make changes to your lifestyle and be more aware of the condition. Remember, just because you have a risk factor doesn’t mean you will definitely develop bowel cancer.

The main factors that can increase your risk of bowel cancer include:


Bowel cancer can affect anyone of any age, but the risk does increase as you get older.

More than nine out of ten new cases (94%) are diagnosed in people over the age of 50, and nearly six out of ten cases (59%) are diagnosed in people aged 70 or over.


A diet high in red and processed meat has been found to increase bowel cancer risk, whilst diets with a high proportion of fruit, vegetables, whole grains and fibre are found to decrease risk.

A 2019 study by Cancer Research UK analysed data from half a million UK adults over almost seven years and found that moderate processed and red meat eaters (those eating 79g per day on average) had a 32% increased risk of bowel cancer compared to people eating less than 11g of red and processed meat daily.


13% of bowel cancers are linked to obesity (having a BMI above 30), and there appears to be a stronger link between obesity and colon cancer in men.

People who have low physical activity levels also have a higher risk of developing bowel cancer.

Long-term smoking is also known to increase the risk of bowel cancer, as does heavy alcohol consumption.

Family history

A strong family history of bowel cancer (having several relatives diagnosed with it), can double your risk of developing the disease compared to the average risk (25%).

Bowel cancer caused by genetic defects can also lead to bowel cancer that occurs at a younger age than is common.


Certain racial groups are known to have higher bowel cancer incidence and mortality rates.

Ashkenazi Jews, for example, have several genetic mutations that cause them to have one of the highest risks of bowel cancer among any ethnic group in the world. African Americans also demonstrate a higher risk, although the reason for this is yet to be established.

Other medical conditions

Some digestive disorders, such as ulcerative colitis and Crohn’s disease, can increase the risk of developing bowel cancer — especially in those who have had one for over 10 years.

Symptoms of bowel cancer

Many of the signs and symptoms of bowel cancer can also be associated with other less serious conditions such as haemorrhoids (piles), irritable bowel syndrome (IBS), diverticular disease, infection or inflammatory bowel disease (ulcerative colitis/Crohn’s disease).

For this reason, if you have any of the symptoms of bowel cancer listed below, you should seek the advice of your GP immediately as well as further tests to confirm a diagnosis.

The symptoms of bowel cancer to look out for are:

  • Blood in your stools or bleeding from your bottom
  • A change in your bowel habits that lasts longer than three weeks (this may include an increase in the frequency of passing stools or having diarrhoea or constipation)
  • Unexplained weight loss
  • A constant or intermittent pain in your tummy
  • A lump in your tummy that doesn’t go away
  • Extreme tiredness for no particular reason
  • A feeling that you haven’t fully emptied your back passage after going to the toilet

As the disease progresses there may be other signs of bowel cancer to look out for. Bleeding may occur internally in the bowel but not be evident in the stool, leading to anaemia. This may cause symptoms such as:

  • Breathlessness
  • Dizziness
  • Tiredness
  • Looking pale

Bowel obstruction

In some cases, bowel cancer can cause an obstruction in your bowel. A bowel obstruction is a medical emergency. If you have any of the symptoms listed below or think your bowel is obstructed go to the accident and emergency department of your nearest hospital straight away.

Signs and symptoms of a bowel obstruction include:

  • Nausea, vomiting and abdominal pain
  • Constant bloating or swelling of your tummy – particularly in the area around your belly button
  • Difficulty passing stools and/or passing wind/gas
  • Unintentional weight loss with persistent abdominal pain
  • Abdominal pain brought on by eating

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How is bowel cancer diagnosed?

If you are experiencing any of the symptoms listed above, it’s important to see your GP to see if any investigations are required.

When diagnosed at the earliest stage (stage 1) around 90% of people will survive for five years or more. However, when diagnosed at the latest stage (stage 4) this drops significantly to just 10% of people. This is why it is essential to seek a diagnosis as soon as you notice any symptoms.

There are a number of tests that can be done to look for bowel cancer and make a diagnosis. Initial tests depend on the symptoms you have. You may need to have additional follow-up tests.

Bowel cancer screening: home test kits

Early screening for bowel cancer can be done before symptoms appear using a faecal immunochemical test (FIT). This involves collecting a small sample of your stool and testing it for traces of blood.

At Check4Cancer, we provide reliable screening that you can do at home with our BowelCheck test kit.

Flexible sigmoidoscopy

A flexible sigmoidoscopy uses a device called a sigmoidoscope (a long, thin, flexible tube with a very small camera and light at the end) that is inserted into your bottom and up into the lower part of the bowel. This produces images of the inside of the bowel.

It can also be used to take a biopsy (sample of tissue) if needed.


A colonoscopy is an examination done under sedation that looks at your entire large bowel using a device called a colonoscopy (a long sigmoidoscope) to identify any abnormal areas within the rectum or bowel that could be caused by cancer.

CT colonography

CT colonography, also called a virtual colonoscopy, is less invasive than a colonoscopy. It can be used to identify potentially cancerous areas of the bowel in people who can’t have a colonoscopy.

During the procedure, gas is pumped into the bowel using a thin, flexible tube before CT scans are taken from different angles.

Imaging scans

If a diagnosis of bowel cancer is made, additional imaging in the form of MRI, CT and ultrasound scans are usually done to see if the cancer has spread to any other parts of the body.

You can read more on the tests used to detect bowel cancer in our ‘How is bowel cancer diagnosed?’ blog post.

Stages of bowel cancer

The tests and scans used to diagnose bowel cancer can also help your doctor determine its stage and grade.

The stage of bowel cancer tells you how far it has grown through the bowel wall and whether it has spread to other areas of the body.

Bowel cancer stages:

  • Stage 1 – the cancer hasn't spread outside the bowel’s inner lining or muscle wall
  • Stage 2 – the cancer has grown into or through the outer wall of the bowel or into tissue or organs next to the bowel
  • Stage 3 – the cancer has spread to nearby lymph nodes
  • Stage 4 – the cancer has spread to other parts of the body, such as the bones and other organs

The grade tells you how the cancer cells look and behave compared to normal cells, suggesting how quickly the cancer could grow.

Bowel cancer cell grouping:

  • Grade 1 – the cancer cells look similar to normal cells and are slow-growing
  • Grade 2 – the cancer cells look different to normal cells but are slow-growing
  • Grade 3 – the cancer cells look very abnormal and are fast-growing
  • Grade 4 – the cells look completely different from normal cells and grow very fast

Knowing the stage and grade of your cancer will help you and your doctor to decide on the best course of treatment for you.

For more information, please refer to our blog article on the stages of bowel cancer.

Treatment for bowel cancer

How doctors treat bowel cancer depends on the stage of the disease at diagnosis and the location of the cancer in the bowel. Depending on how advanced the cancer is, you may also need to have multiple types of treatment.

Treatment options for bowel cancer include:


Surgery is the most common treatment for bowel cancer that hasn’t spread, as it removes any areas of tissue affected by the disease. The type of operation you may have will depend on where the cancer is in the bowel.


Radiotherapy can be done at different stages of treatment and can be effective in killing cancer cells, shrinking cancer, slowing the spread and controlling symptoms.


Chemotherapy can be taken orally with tablets or, given intravenously through a drip in your arm, or as a combination of both, to try to kill cancer cells.

Targeted therapies

Targeted therapies are medicines designed to attach to and kill specific cancer cells or cells that help cancer cells grow to shrink tumours and improve the effect of chemotherapy.

How to reduce the risk of bowel cancer

Although the exact cause of bowel cancer isn’t clear, there are a number of changes you can make to your lifestyle that can significantly reduce your risk of bowel cancer, including:

  • Eating less red or processed meat
  • Eating a healthy balanced diet that includes fruit, vegetable, whole grains and fibre
  • Reducing your weight if overweight or obese
  • Reducing your alcohol intake
  • Stopping smoking – find out more about starting a smoking cessation programme in the NHS
  • Having regular bowel cancer screening from age 45+ 

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Getting tested: bowel cancer screening

Bowel cancer screening can help to detect cancers in their earliest stages and ensure you get treatment early. Screening can also detect the non-cancerous lesions (polyps) that may subsequently turn into cancer, and allow these to be removed, thus preventing bowel cancer from forming.

There is an NHS bowel cancer screening programme in the UK, BUT it is only available to people aged 60 or above (50 or above in Scotland). Since bowel cancer rates start to increase from the age of 45, it is possible to be tested privately with BowelCheck from this age.

Unlike the NHS bowel cancer screening programme, BowelCheck is available to anyone over the age of 45 and the testing mechanism is more advanced leading to more accurate results. No bowel cancer screening test can be guaranteed to be 100% accurate, and a positive result from BowelCheck will mean that further investigations are likely to be recommended.

The prognosis for bowel cancer can be very good if it is detected at the very early stages, which is why bowel cancer screening like BowelCheck is so important.

How can I get tested?

If you are worried about bowel cancer, Check4Cancer has developed BowelCheck, a simple testing kit that you can use in the comfort of your own home.

Initial tests for bowel cancer detect the presence of blood in a stool sample. This is known as a faecal immunochemical test (FIT) and involves sending a sample of stool to the lab for testing. If blood is detected, further investigations will be necessary.

Faecal immunochemical tests are sometimes recommended for people aged 45 and older to check for the early signs of bowel cancer. They may also be recommended if you have a family history of bowel cancer.

Order your bowel cancer test kit

BowelCheck is a bowel cancer screening qFIT test that looks for signs of digested human blood in your stools as this can be a sign of bowel cancer.

BowelCheck can be carried out in the comfort of your own home and is quick, hygienic and easy to use.

Check for bowel cancer by ordering your Check4Cancer BowelCheck test today.

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Order your BowelCheck test today

Order your BowelCheck test today

BowelCheck is a bowel cancer screening qFIT test that looks for signs of digested human blood in your stools as this can be a sign of bowel cancer. BowelCheck can be carried out in the comfort of your own home and is quick, hygienic and easy to use.