Bowel (colorectal) cancer usually grows slowly and often causes no symptoms in its early stages. Screening means testing people who feel well, so that problems are found early or prevented altogether. Colonoscopy is the most complete screening test for the large bowel. This article explains why it matters and who should consider it.
Why screening matters
Most bowel cancers start as polyps, which are small growths on the inner lining of the bowel. Polyps take years to turn into cancer and usually cause no symptoms. During a colonoscopy they can be found and removed in the same sitting, which prevents the cancer from developing. When cancer is already present, finding it early makes treatment simpler and more successful.
Who should consider screening?
- Adults from middle age onwards, even without symptoms; your doctor will advise the right age to begin
- People with a parent, brother, sister or child who had bowel cancer or polyps, who may need to start earlier
- People who have had polyps removed before
- People with long-standing inflammatory bowel disease
- Families with a known inherited bowel cancer condition
If you already have symptoms such as bleeding, a change in bowel habit or unexplained anaemia, you need a diagnostic test, not screening. Please see a doctor without waiting.
How a colonoscopy is done
A thin, flexible tube with a camera is passed through the back passage to examine the whole large bowel. The test is usually done with sedation so that you are comfortable. If a polyp is seen it can be removed, and small samples (biopsies) can be taken. Read more about colonoscopy and endoscopic care.
Preparing for the test
A clean bowel is essential for an accurate test. You will be given written instructions about diet and a bowel-cleansing medicine to take beforehand. Tell your doctor about your medicines, especially blood thinners, iron tablets and diabetes medicines, as some may need to be adjusted.
Is it safe?
Colonoscopy is a commonly performed and generally safe test. Complications such as bleeding or injury to the bowel are uncommon, and are slightly more likely when a large polyp is removed. Your doctor will explain the risks before the procedure.
How often should it be repeated?
That depends on what is found. After a normal test, the next one may not be needed for several years. If polyps are removed, you will be advised to return sooner. Your doctor will give you a follow-up plan.
Other ways to lower your risk
- Eat more vegetables, fruit and fibre, and less red and processed meat
- Stay physically active and keep a healthy weight
- Avoid tobacco and alcohol
Frequently asked questions
Is colonoscopy painful?
With sedation most people feel little or no discomfort. Some bloating afterwards is common and passes quickly.
Can I go home the same day?
Yes, in most cases. Bring someone with you, because you should not drive or travel alone after sedation.
I have no symptoms. Do I still need it?
Screening is meant for people without symptoms. Whether and when you need it depends on your age and family history, which you can discuss at a consultation.
To ask about screening, request an appointment or see the chamber timings.
This article is for general awareness and does not replace a consultation with a doctor.