Bowel cancer tests
This page tells you about tests for bowel cancer (also called colon cancer or colorectal cancer). You can find the following information
Bowel cancer tests
Usually you begin by seeing your GP, who will ask about your general health, examine you and do some blood tests. They may examine your back passage (rectum). Your doctor may then refer you to hospital to see a specialist and for further tests.
At the hospital
A bowel specialist will ask about your medical history and symptoms. The doctor or a specialist nurse can use a tube to look inside the back passage and lower part of the large bowel. This test is called a sigmoidoscopy. You usually have this done in the outpatient department. To have a sigmoidoscopy, you must have an empty lower bowel. You usually need to have a small enema or strong laxatives beforehand to clear your bowel out.
If they can see any abnormal areas, the doctor or nurse will take samples (biopsies). If you have any growths of the bowel lining (polyps), they will remove them and send them away to be looked at under a microscope.
Your doctor may advise you to have a colonoscopy. This test looks at the whole of the inside of the large bowel. You have it in the outpatient department and it takes about an hour. For this test the bowel has to be empty. You will probably have medicine to make you drowsy just before the test. The doctor or nurse will ask you to lie on your side and will pass a flexible tube into your back passage and up into your bowel. They can take photographs and biopsies of the bowel lining during the test.
In some cases, your doctor may arrange for you to have a CT colonography (virtual colonoscopy). This uses CT scans to look at the inside of the large bowel. Occasionally you may have a barium enema, which shows an outline of the bowel using X-rays.
You can view and print the quick guides for all the pages in the diagnosing bowel cancer section.
Usually you begin by seeing your GP who will ask about your general health and may examine your back passage (rectum). This is called a rectal examination. You may have a blood test to check for anaemia. Anaemia is common in people with bowel cancer but may also be caused by other conditions. You may have blood tests to check if your liver and kidneys are working normally. Your GP may then refer you to hospital to see a specialist and for further tests.
Read about what happens and what you can do if your GP makes an urgent referral for you.
The bowel specialist will ask about your medical history and symptoms, and will probably examine your back passage. You may have this done in the clinic with a sigmoidoscopy, which examines the back passage and the lower part of your bowel. The specialist may also want to examine the rest of your bowel with a colonoscopy.
Your GP or the specialist at the hospital may do a rectal examination. They do this by putting a gloved finger into your back passage and feeling for any lumps or swelling. The examination may be uncomfortable but should not be painful.
This test allows the doctor or a specialist nurse to look inside the back passage or the lower part of the large bowel. There are 2 types of sigmoidoscopy – a rigid sigmoidoscopy (also called proctoscopy) and a flexible sigmoidoscopy.
The rigid sigmoidoscopy has a short, hard, inflexible tube and can check the lining of the back passage.
The flexible sigmoidoscopy tube is longer, flexible and can see the back passage and also the lower part of the large bowel on the left hand side. This area is where most polyps and bowel cancers start.
You usually have sigmoidoscopy in the outpatient department. You don't usually need an anaesthetic or medicine to make you drowsy. To have a sigmoidoscopy you must have an empty lower bowel. So you usually need to have an enema or take strong laxatives beforehand to clear your bowel out. Your doctor or nurse may arrange for you to do this at home the day before you go into the department for the test.
Once at the hospital, a nurse may ask you to change into a hospital gown. Under your gown you may also have paper trousers with a hole cut out of the back. Then the doctor or nurse will ask you to lie on the examination table on your left side. The doctor or nurse puts a thin tube called a sigmoidoscope into your back passage and up into the large bowel. This is not usually painful but it is uncomfortable. If you find it too uncomfortable at any stage, just tell the doctor or nurse and they will stop. Once the tube is in place, they pump a little air or carbon dioxide into your bowel. The air inflates the bowel slightly and helps them to see the bowel wall more clearly.
If they can see any abnormal areas the doctor or nurse will take samples (biopsies) with the sigmoidoscope. If you have any growths of the bowel lining (polyps) they will snip these off and send them away to be looked at under a microscope. The whole procedure takes about 5 minutes. It may take a little longer if they need to remove any polyps, but even then the test only takes about 10 to 15 minutes.
You should be able to go home as soon as the test is over. Some people have a small amount of bleeding from the back passage after sigmoidoscopy, particularly if they have had polyps removed. This is normal and usually clears up on its own over a few days.
A colonoscopy looks at the whole of the inside of the large bowel. You have this test in the outpatient department and it takes about an hour.
Below is an animation showing what to expect when you have a colonoscopy.
View a transcript of the video about having a colonoscopy (opens in a new window).
The bowel needs to be empty. You will be given a list of things to help prepare your bowel for the test. These are likely to include
- Stopping iron tablets
- Not eating solid food for 1 or 2 days before the test
- Drinking plenty of clear fluids
- Taking laxatives
After taking the laxatives you will need to go to the toilet often. The need to go may be very sudden. You may also have stomach cramps. You will need to stay at home at least for a few hours after taking the laxatives so that you are close to a toilet.
When you arrive at the hospital, the nurse or a technician will give you a gown to change into. They may also give you paper shorts to wear, which have an opening at the back.
You will probably have medicine to make you drowsy just before the test. This is called a sedative. In some hospitals you may have gas and air (Entonox) instead.
The doctor or nurse (called a colonoscopist) will ask you to lie on your side. They will pass a flexible tube into your back passage and up into your bowel. As the tube bends easily it can pass around the curves in the bowel. So your doctor or nurse can examine the lining of the whole length of your bowel. The light inside the tube helps them to see any problem areas or swelling. They can take photographs and biopsies of the bowel lining during the test. Your doctor or nurse may also spray a dye onto the lining of the bowel to make abnormal areas show up more clearly. This is called chromoscopy.
You should be able to go home a couple of hours after the test. You shouldn't drive for about 24 hours after having the sedative. If you have had a sedative you should have someone with you to take you home. If you live alone, ideally they should stay overnight just to make sure that you are all right.
Colonoscopy is a very safe test. But like all medical tests it does have risks. There is a very small risk of making a hole in the bowel wall called a perforation. Although this is rare, it is serious. You would have to go to the operating theatre for emergency surgery to repair your bowel wall. And you would need strong antibiotics to prevent infection.
CT colonography is also called virtual colonoscopy. Instead of having the colonoscope put inside your bowel, the doctor looks at pictures created by a computer.
Before the test you have laxatives and plenty of fluids to clear out your bowel. You also follow a special diet for a couple of days beforehand. Your doctor or nurse will give you full details. The test uses a CT scanner, so you have this test in the CT scanning department. You can have it as an outpatient.
Just before the test the radiographer puts a small tube into your back passage to pump carbon dioxide or air inside. This helps to open up the bowel, which gives clearer pictures on the scan. You then have 2 CT scans done. You have one scan lying on your back and one lying on your front. A computer matches up the 2 scans and makes a virtual scan of the inside of your bowel. This shows up any growths on your bowel wall. You may still need to have a colonoscopy if you need a biopsy.
This is an X-ray of the large bowel. Doctors occasionally use it instead of CT colonography.
Barium is a white liquid that shows up clearly on an X-ray. The barium coats the inside of the large bowel and rectum, and shows the outline on the X-ray. This can show any growths or abnormal areas. If you need a biopsy, you will need to have a colonoscopy.
We have more information about having a barium enema.
After your tests for bowel cancer you usually go back to the hospital to get your results. This is bound to take a little time, even if only a week or so. Understandably, this is a very anxious time for most people.
While you are waiting for results it may help to talk to a close friend or relative about how you are feeling. Or you may want to contact a cancer support group to talk to someone who has been through a similar experience.
Look at the bowel cancer organisations page for organisations that can put you in touch with a support group. There are also details of organisations that can tell you more about counselling and help you to find sources of emotional support and counselling in your area.
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