Bowel Cancer Screening

Prostate Health

Bowel Cancer screening saves lives

Bowel cancer is the third most common cancer in the UK, affecting around one in 14 men and one in 19 women. After lung cancer, it causes the most deaths. The good news is that, if it is diagnosed early, bowel cancer can nearly always be cured. That is why healthcare professionals consider bowel screening so important.

Why should I get tested?

In short, bowel screening and early detection of cancer could save your life. Early detection and treatment substantially increases survival rates – more than 9 out of 10 people survive their cancer for five years or more. Survival rates are much lower when cancer is detected at a late stage.

Screening not only detects bowel cancer at an early stage, it can frequently prevent it. Doctors believe that bowel cancer takes between 10 and 15 years to develop, so detecting polyps as soon as possible means they can be removed before they become cancerous.

Who is most likely to be affected?

Bowel cancer screening can detect problems within the colon at an early stage, when treatment is most likely to be successful. During a colonoscopy, polyps are removed to prevent them from becoming cancerous. This is not possible with other screening tests such as CT colonography (a.k.a “virtual colonoscopy”).

As around 95% of people with bowel cancer are aged over 50, we usually advise people to begin regular screening at about this age, even if they have no symptoms.

However, if you are younger, there is nothing to stop you making an appointment, particularly if you have a family history of bowel cancer, or you are worried.

Why do we recommend colonoscopy?

There are a number of different tests that look for bowel cancer including:

Faecal Occult Blood test (FOB)

This looks for blood in your faeces and is a simple and inexpensive test. The NHS uses it because there is research evidence that a FOB test followed by a colonoscopy reduces colon cancer rates by about 30%.

The weakness of an FOB test is that it is not very sensitive nor specific for cancer. Many patients with premalignant polyps (which can grow into tumours) don’t have blood in their stool. And some of those with a positive test result may in fact have no significant problem at all – brushing your teeth too hard can trigger a ‘false positive’, for example.

Flexible sigmoidoscopy

This involves passing a thin, flexible tube with a miniature camera on the end (an endoscope) through the anus to examine the rectum and the lower parts of the colon. The lower bowel needs to be cleansed with an enema beforehand.

Although the test is highly sensitive and specific for cancerous polyps, the test only examines about 1/3 of your colon, so cancers and polyps higher in your bowel can be easily missed.

CT scan (virtual colonoscopy)

CT scanning images your entire large bowel. The test involves lying in a scanner after gas has been pumped into the colon through a small tube inserted through the anus. It has the advantage of screening the whole colon but does require laxatives to cleanse the bowel, taken the day before, and does involve exposure to radiation.

In expert hands and with first-rate CT scanning, early experience suggests it is accurate for detecting cancers and most large polyps, but less accurate for smaller or flat polyps. It is purely diagnostic and cannot remove polyps.

Abnormalities found at CT colonography usually mandate a subsequent conventional colonoscopy to remove any polyps or take biopsies from any suspected cancer.

Visual Colonoscopy

Although using any of the previous tests might be appropriate in some circumstances, London City Healthcare only fully endorses visual colonoscopy for screening because it is the most effective and reliable screening test for polyps and bowel cancer.

In the United States, it is the gold standard because of its exceedingly high levels of accuracy in the hands of genuine experts, and the ability for your consultant to combine diagnosis and treatment in one step.

Conventional (or ‘visual’) colonoscopy involves passing an endoscope through the anus to examine all the areas where polyps and cancer can occur. It is the one test that allows your doctor to see the entire bowel, both lower and upper sections, and to remove precancerous polyps at the same time. As with CT scanning, patients take a bowel preparation the day before to cleanse the colon completely.

Modern video endoscopes give high definition colour images that are superior to looking directly at the bowel wall with the naked eye. If polyps or cancer are detected they are removed and biopsied through the instrument, on the spot. The specimen is then sent to pathology for analysis, which can take up to five days for the results. The procedure is definitive, combining diagnosis and treatment in one test.

Colonoscopy is highly operator dependent, in that the comfort, accuracy and risks of the procedure are directly related to the skill and experience of the doctor performing it. All the endoscopists we recommend are highly trained and experienced consultant gastroenterologists who take part in an ongoing quality assurance programme to demonstrate their continuing expertise.

Like all procedures, colonoscopy has risks and benefits that you should discuss fully with your doctor before the procedure. Although there are many excellent facilities and competent specialists in London, the centres we recommend stand apart for a number of key reasons, none more important than their outstanding safety and clinical care record.

Please contact our team on 020 7236 3334 for any further information, assistance or support.


Thiis-Evensen E, Hoff GS, Sauar J, et al.: Population based surveillance by colonoscopy: effect on the incidence of colorectal cancer. Telemark Polyp Study I. Scand J Gastroenterol 34 (4): 414-20, 1999

Lieberman DA, Weiss DG, Bond JH, et al.: Use of colonoscopy to screen asymptomatic adults for colorectal cancer. Veterans Affairs Cooperative Study Group 380. N Engl J Med 343 (3): 162-8, 2000

Imperiale TF, Wagner DR, Lin CY, et al.: Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings. N Engl J Med 343 (3): 169-74, 2000

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