Diagnosing bowel cancer
You usually have a number of tests to check for bowel cancer. The tests you may have include:
a test that looks for blood in your poo. This is a Faecal Immunochemical Test (FIT)
looking at the whole of the inside of your large bowel using a flexible tube (colonoscopy) or to look at the lower part of the bowel (sigmoidoscopy)
scans to look at your bowel. These might include a CT colonography or a CT scan of your tummy (abdomen) and
Bowel (or colorectal cancer) means cancer that starts in the large bowel (colon) or the rectum (back passage). This is different from cancer that starts in the anus or small bowel.
Find out about small bowel cancer
Most people with symptoms that could be due to cancer start by contacting their GP surgery. Your first appointment may be a telephone appointment. Your GP surgery then might arrange for you to go in and see a doctor or other healthcare professional.
The tests your GP might do include one or more of the following:
an examination of your abdomen (tummy), anus and rectum
a test that looks for tiny traces of blood in a sample of your poo - a Faecal Immunochemical Test (FIT)
blood tests
Your GP may also ask you for another sample of poo to check for inflammation in the bowel. This is to test for a protein called faecal calprotectin. Your GP or practice nurse will give you a sample pot to take away with you. You bring it back once you have collected the poo sample.
FIT is a test that looks for tiny traces of blood in poo that are too small to see. Blood in poo can be caused by a number of medical conditions but it can also be a sign of bowel cancer.
You do this test yourself at home. Your GP will give you the test kit or they will arrange for you to get one in the post.
An examination of the rectum is also called a digital rectal examination (DRE). It involves your doctor feeling inside your anus and rectum using their gloved finger. They use so it’s more comfortable for you. They feel for any lumps or hard areas.
It’s normal to feel anxious about this test but it usually only takes less than a minute. You can ask for someone else to be in the room if you want, to act as a chaperone. This chaperone can be a friend or relative, or a health professional such as a practice nurse.
Find out more about having an examination of your rectum
Your doctor may also feel your tummy (abdomen) for any areas that are swollen or might not feel normal. And if you have any pain, they will feel those areas. They may also listen to your abdomen to find out if it sounds normal.
Blood tests can check your general health, including how well your liver and kidneys are working. Your doctor can also check the number of such as red blood cells.
Your doctor might also check your levels if you are .
Find out more about blood tests
Depending on the results of your examination and FIT, your GP might refer you to a specialist. You are usually referred to a lower gastrointestinal (lower GI) clinic where you might see a GI specialist nurse or a colorectal doctor.
Your specialist does more tests. These might include:
colonoscopy
flexible sigmoidoscopy
CT colonography
CT scan of your tummy (abdomen) and
colon capsule endoscopy
A colonoscopy looks at the whole of the inside of your large bowel using a flexible tube called a colonoscope. The tube has a small light and camera at one end and your doctor can see pictures of the inside of your bowel on a TV monitor.
You usually have this test in the endoscopy department of the hospital. You need to take the day before your test to empty your bowel.
During the test, your doctor can take tissue samples (biopsies) of any abnormal areas. They send the biopsies to the laboratory to check for bowel cancer.
Read more about having a colonoscopy
Click on the link above to watch an animation about having a colonoscopy.
A flexible sigmoidoscopy looks inside the lower part of your large bowel using a flexible tube. This is also called a bowel scope or flexi sig.
A flexible sigmoidoscopy is similar to a colonoscopy. But it only looks inside the anal canal, rectum and the lower part of your large bowel, whereas a colonoscopy looks at the entire bowel.
Find out more about having a flexible sigmoidoscopy
CT colonography is a test that uses a CT scan to check the large bowel and rectum. CT stands for computer tomography. It uses x-rays and a computer to create detailed pictures of the inside of your bowel.
You need to have an empty bowel for this test, so you take medicines to empty your bowel the day before.
Find out more about having a CT colonography
You might have a CT scan to help diagnose bowel cancer if you’re not able to have . The scan looks at your tummy (abdomen) and the area between your hip bones (pelvis).
A CT scan is a test that uses x-rays and a computer to create detailed pictures of the inside of your body. It takes pictures from different angles. The computer puts them together to make a 3 dimensional (3D) image.
Find out about having a CT scan
A colon capsule endoscopy looks at the inside of your large bowel (colon) using a capsule that you swallow. The capsule is the size of a large pill. It has a small wireless camera that sends pictures of the inside of your bowel to a data recorder.
You might have a colon capsule endoscopy instead of a colonoscopy straight away. It can help to rule out bowel cancer. This test isn’t available in most hospitals at the moment.
Read more about having a colon capsule endoscopy
If you have a that shows that you have bowel cancer, you may have more tests to work out where and how big the cancer is. This is called staging the cancer. Doctors can also do tests on the biopsy sample itself.
The tests you might have include:
tests on your bowel cancer cells
CT scan
PET-CT scan
MRI scan of the area between your hip bones (pelvis) or liver
ultrasound scan of the tummy (abdomen) or back passage (rectum)
After a doctor removes tissue or cancer from your bowel, they send the samples to a laboratory. A doctor called a pathologist does various tests on the cells. These tests can help to diagnose bowel cancer and look for certain changes.
Knowing about gene changes can help your doctor decide the best treatment for you. This is because certain treatments work better if you have certain gene changes.
Your might have tests on the cancer cells for changes in the following genes:
MSI
RAS
BRAF
There are different gene changes that your doctor may test for. It all depends on your individual circumstances. You can ask your doctor what tests they will do on your bowel cancer cells.
Find out more about the tests you might have on your bowel cancer cells
You might have a CT scan of your chest, abdomen and the area between your hip bones (pelvis). This is to check where the cancer is and whether it has spread to other parts of the body.
Read more about having a CT scan
A PET-CT scan combines a CT scan with a PET scan to give detailed information about the cancer. You might have a PET-CT scan to:
check whether the cancer has spread to other parts of the body
help decide the best treatment for you
show how well the treatment is working
check whether the cancer has come back
Find out more about having a PET-CT scan
MRI stands for magnetic resonance imaging. It uses magnetism and radio waves to create pictures of the inside of the body.
You may have an MRI scan help rectal cancer.
You might also have an MRI scan of your liver. The liver is a common place for bowel cancer to spread because blood flows directly from the bowel to the liver.
Read more about having an MRI scan
Ultrasound scans use high frequency sound waves to create a picture of a part of the body. They can show up changes including abnormal growths. You may have an ultrasound scan of your abdomen to check whether the cancer has spread.
You may also have an ultrasound scan of your rectum. An ultrasound scan of the rectum is also called transrectal ultrasound scan (TRUS). You may have this if you have rectal cancer.
Find out more about having an ultrasound scan
Tumour markers are substances that are produced by the cancer or other cells of the body in response to cancer or other conditions. They’re usually proteins that can be found in the blood, urine or body tissues.
Some tumour markers are only produced by one type of cancer. Others can be made by several types.
Doctors might use tumour markers to monitor how well your cancer treatment is working or check if the cancer has come back.
For bowel cancer, your doctor might test for a tumour marker called carcinoembryonic antigen (CEA).
All the tests you have help your doctor find out about the stage of the cancer.
Read about the stages of bowel cancer
This is important because doctors recommend your treatment according to the stage of the cancer.
Find out about the treatment options for bowel cancer
Coping with a diagnosis of bowel cancer can be difficult. There is help and support available to you and your family.
Last reviewed: 27 Nov 2024
Next review due: 27 Nov 2027
Bowel cancer is also called colorectal cancer. It affects the large bowel, which is made up of the colon and rectum.
Symptoms of bowel (colorectal) cancer can include bleeding from the back passage, blood in your poo or a change in your normal bowel habit.
FIT (Faecal Immunochemical Test) is a test that looks for blood in a sample of your poo. It looks for tiny traces of blood that you might not be able to see and which could be a sign of cancer.
Treatment depends on whether you have colon or rectal cancer, as well as your cancer stage. You might have surgery, radiotherapy or chemotherapy or a combination of these.
Your GP should arrange for you to have tests or to see a specialist if you have symptoms that could be due to bowel cancer.
Bowel cancer means cancer that starts in the colon (large bowel) or back passage (rectum). It is also known as colorectal cancer.
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