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Bowel cancer screening: having a colonoscopy

Updated 28 July 2022

We send this leaflet to everyone who needs further tests after completing the bowel cancer screening test (the FIT kit). Needing further tests means we found blood in the sample of your poo (also known as faeces, stools or bowel motions). To investigate this we use an examination called colonoscopy.

Appointment 1: specialist screening practitioner clinic

First we offer you an appointment with a specialist screening practitioner (SSP) to discuss having a colonoscopy. The SSP will:

• talk to you about your screening results
• describe what happens during a colonoscopy
• explain the possible risks and benefits
• ask some questions about your health
• answer any questions you have

The SSP will assess if you are fit enough for a colonoscopy. If you are, it is your choice whether to go ahead with the investigation.

Appointment 2: colonoscopy

If you decide to go ahead, we will send you an appointment for colonoscopy at a bowel cancer screening centre. This appointment will usually be about 2 weeks after your SSP appointment.

The colon and rectum make up the large bowel

Bowel cancer and polyps

Bowel cancer is also known as colon, rectal or colorectal cancer. Sometimes the cells that make up the bowel grow too quickly and form a clump of cells known as a bowel polyp (some types of polyp are called an ‘adenoma’). Polyps can sometimes change into a cancer over a number of years. Colonoscopy looks for polyps and bowel cancers.

Colonoscopy

Colonoscopy takes place at NHS bowel cancer screening centres, usually in hospitals. A colonoscopist (someone specially trained in colonoscopy) carries out the examination.

The colonoscopist uses a thin flexible tube with a tiny camera on the end to look inside your bowel. Colonoscopy can find bowel cancer. It can also find polyps, which can usually be removed to stop them growing into cancers.

Colonoscopy usually takes 30 to 45 minutes, although the whole appointment may take around 2 hours.

Colonoscopy is not appropriate for some people. Some health issues mean it may not be possible. If this is the case for you, we may offer you another test instead. This will usually be a bowel x-ray called computerised tomography colonography (CTC) - sometimes called a ‘virtual colonoscopy’. If we find any polyps using CTC we will talk to you about the possible benefits and risks of having another appointment to have them removed.

Having the polyps removed is not an option for some people, as the risks of the procedure for them would outweigh the benefits.

Before your colonoscopy

The SSP may give you a list of foods you need to avoid for several days before your colonoscopy. They will also give you a medicine to clear your bowel (a strong laxative). You need to have an empty bowel so the colonoscopist can see the bowel lining clearly.

When you take the medicine will depend on the time of your appointment. The SSP will give you written instructions. Please read them carefully.

It is important you take the medicine according to the instructions. It will cause diarrhoea, so you will need to stay close to a toilet.

You will need to arrange for someone to take you home after your colonoscopy. This is because we may give you a sedative and you could be drowsy.

Having your colonoscopy

When you arrive for your appointment you will be able to talk to the nurses and doctors about any concerns or questions you have.

We will ask you to lie on a bed on your left side with your knees slightly bent up. We may give you a painkiller. We may also give you a sedative. It is your choice whether to have this. It is usually an injection into a vein in your arm. It is to relax you and make colonoscopy more comfortable. Following a sedative, you should not:

• drive home afterwards (you will need someone to take you home)
• drink alcohol for 24 hours
• operate machinery for 24 hours

A colonoscopist will perform your colonoscopy.

1. The colonoscopist will put a colonoscope (thin flexible tube) into your large bowel through your back passage (rectum).
2. They then gently pump some harmless carbon dioxide gas inside. This opens up the bowel so they can see the lining clearly. It may cause a bloating or cramping feeling.
3. The camera on the colonoscope shows the inside of your bowel on a screen.

If you feel pain, let the colonoscopist know. They can change what they are doing to make you as comfortable as possible.

The colonoscopist looks at images from inside the bowel on a screen

After your colonoscopy

The colonoscopist or SSP will tell you if they removed any polyps or tissue samples (biopsies). If they did, we will provide you with the results within 2 weeks. We will also send your GP a copy of your results.

You will probably feel like resting after your colonoscopy. You may want to try and keep the whole day free of work or other commitments.

After the colonoscopy, you may feel sick or have some abdominal (tummy) pain or bloating for a day or so. You may also have some blood in your poo. If the symptoms are severe or do not go away in 2 days, you should see your GP. You can also contact the screening centre where you had your colonoscopy.

Reliability of colonoscopy

Colonoscopy is a good test for finding polyps or cancer in the bowel. But there is a small chance (about 3 out of 100) that colonoscopy misses cancer or a polyp that could later turn into cancer. This could be because:

• the bowel was not completely empty
• it was difficult to move the colonoscope around the bowel
• in rare cases, the colonoscopist could not see the polyp or cancer

Risks of colonoscopy

For most people, colonoscopy is straightforward. But as with most medical procedures, complications can happen. In rare cases, colonoscopy can harm the bowel. Possible complications include:

• a hole (perforation) in the bowel caused by the colonoscope (around 1 person in 1700); around half of people with a perforation will need surgery to repair it
• heavy bleeding needing a transfusion (around 1 person in 2,400)

If you have bleeding that is difficult to stop or a hole in your bowel that needs surgery we will admit you to hospital straightaway.

In rare cases, colonoscopy complications may result in death. However in a national audit of 20,085 colonoscopies carried out in 2011, no deaths were recorded.

Results

No polyps, or small polyps that need no treatment

About 13 in 100 people have this result. It means we found no polyps, or only small polyps that are very unlikely to turn into cancer. No further investigation is needed at this time.

Even if you have this result, it is still important to be aware of the symptoms of bowel cancer. This result does not guarantee that you do not have bowel cancer or that it will never develop in the future. Please see the section on bowel cancer symptoms.

We will invite you for bowel cancer screening again in 2 years’ time if you are still under 75 by then. If you will be 75 or over, you can still ask for a test kit every 2 years by calling our free helpline on 0800 707 60 60. If you have hearing or speech difficulties you can use the Relay UK service to contact us. Dial 18001 then 0800 707 60 60 from your textphone or the Relay UK app.

Polyps or other findings

About 25 in 100 people have small polyps or other findings such as haemorrhoids (piles) or diverticular disease. Usually we remove small polyps painlessly during colonoscopy using a tiny wire loop passed through the colonoscope. The colonoscopist may also take a tiny piece (biopsy) of bowel lining to look at afterwards under a microscope. If you have polyps removed, we may invite you for another colonoscopy to check your bowel again. The timing of this depends on how many polyps we found and how big they were.

Adenomas needing removal

About 53 in 100 people have adenomas that need to be removed. An adenoma is a type of polyp that is more likely to turn into cancer if it is not removed. Sometimes people have an adenoma that is too difficult to remove during colonoscopy. We may offer these people surgery or a further specialist colonoscopy at a later date.

Bowel cancer

About 9 in 100 people have bowel cancer. If we find cancer, we will give you an appointment to see a cancer specialist as soon as possible.

If we find bowel cancer at its earliest stage, 9 out of 10 people (90%) have successful treatment. However not all bowel cancers found at screening can be treated successfully.

Results for every 100 people having colonoscopy after an abnormal FIT kit result

Bowel cancer symptoms

It is still possible to get bowel cancer even if you had:

• no polyps found at colonoscopy
• small polyps we did not need to remove
• small polyps we removed

It is important to be aware of bowel cancer symptoms. These include:

• blood in your poo (faeces)
• looser poo, pooing more often and/or constipation
• a pain or lump in your abdomen (tummy)
• feeling more tired than usual for some time
• losing weight for no obvious reason

Please remember that these symptoms don’t necessarily mean that you have bowel cancer. But if you have any of these symptoms for 3 weeks or more, please speak with your GP. It is important to do this even if you:

• did not need further tests after using the FIT kit
• did not need any treatment during or following colonoscopy

Reduce your risk of bowel cancer

Having bowel cancer screening reduces your risk of dying from bowel cancer by at least 25%.

You can also reduce your risk of bowel cancer by:

• keeping physically active
• keeping a healthy weight
• eating plenty of fibre, for example, choose wholegrain and wholemeal foods
• eating plenty of vegetables and fruit
• eating less red meat and especially less processed meat
• drinking less alcohol
• not smoking

More information and support

If you have any questions or concerns about having a colonoscopy, call our free helpline on 0800 707 60 60.

If you have hearing or speech difficulties you can use the Relay UK service to contact us. Dial 18001 then 0800 707 60 60 from your textphone or the Relay UK app.

You can also:

• talk to your GP
• visit the NHS.UK website
• visit the GOV.UK website and search for ‘bowel cancer screening’

The NHS screening programmes use personal information from your NHS records to invite you for screening at the right time. NHS England also uses your information to ensure you receive high quality care and to improve the screening programmes. Find out more about how your information is used and protected, and your options.

Find out how to opt out of screening.

About this information

The following images in this document are used under licence. Contact the copyright holder/s to obtain permission for any further use.

Diagram of the large bowel: metamorworks/Shutterstock

Reference: BCSP15
PN6451755