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CT colonography: a less-invasive test for bowel cancer

A new, non-invasive test can help diagnose colon cancer. Called the FIT test (faecal immunochemical test), it can be done at home and is more accurate at detecting blood in stools.


Until the FIT test becomes mainstream, asymptomatic patients over 60 years of age, who are invited to take part in the NHS Bowel Cancer Screening Programme, are sent a guaiac faecal occult blood test (gFOBT), where a stool sample is tested for the presence of blood.

The new FIT test is more sensitive, which means health professionals can be more certain you do not have a bowel cancer if the test is negative.

I have had a positive FIT test, does this mean I have a bowel cancer?

While a negative FIT test can exclude a bowel cancer, a positive FIT test does not mean you have a bowel cancer. There are a number of reasons a FIT test can be positive, but it does mean you need a formal examination of the bowel.

Colonoscopy is considered the gold-standard test to exclude or diagnose bowel cancer. It uses a long, thin, flexible tube that contains a camera, which is inserted into the rectum and passed around the bowel to look for a cancer or polyp. It is a safe test that most people tolerate.

Are there any tests that do not involve colonoscopy to detect bowel cancer?

Another test, called a CT colonography, has been shown to be equal to a colonoscopy to detect bowel cancers and large polyps in many clinical trials.

CT colonography is often better tolerated than a colonoscopy, is considered less-invasive and the preparation is less demanding as the laxatives used are not as strong. It also takes less time, and sedation – which is sometimes needed for colonoscopy – is not required.

It involves having a computerised tomography (CT) scan of the tummy after taking a drink preparation called gastrograffin. During the scan, gas is used to inflate the bowel using a small tube passed into the rectum.

The scan produces a ‘virtual colonoscopy’ that a radiologist can then assess on a computer work-station and report back to your doctor.

CT colonography can be used to assess the bowel in patients with symptoms of bowel cancer and/or a positive FIT test and is used in the screening programme when colonoscopy fails or is not possible.

Another advantage of CT colonography is that it will also look at your other abdominal organs such as the liver, pancreas and kidneys.

I have rectal bleeding, is a CT colonography a good test?

If you have rectal bleeding a CT colonography can be used, however a flexible sigmoidoscopy would be the first examination recommended after an examination of the bottom known as a digital rectal examination (DRE).

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