Colorectal cancer is the commonest cancer in Singapore. It is curable if detected and operated on at an early stage; it is preventable if colorectal polyps can be detected and removed before they have a chance to become malignant. The problem is how to achieve this.
The usual symptoms for colorectal cancer are change in bowel habit (diarrhoea or constipation) for more than three weeks, blood in the stools, mucus discharge, vague abdominal discomfort, abdominal lump, loss of appetite and loss of weight. These symptoms are not specific to cancer as they can also be due to common conditions like piles, Irritable Bowel Syndrome (IBS), diverticular disease and just common constipation or diarrhoea. Furthermore, 20-25% of colorectal cancer has no symptoms at all until the late stage. Patients often say "I didn't know I have cancer because I don't feel any pain at all". Early colorectal cancer has no pain. It appears only in the terminal stage.
The most effective way to detect colorectal cancer polyps is through colonoscopy. It is a direct examination of the entire colon and rectum with a flexible fibreoptic scope. It also enables doctors to take biopsies and remove polyps. As nearly all colorectal cancer develop from polyps, their removal prevents cancer.
If a patient has colorectal symptoms, colonoscopy will allow his doctor to make an accurate diagnosis, to differentiate benign conditions from cancer. In Singapore, many people are paranoid about colorectal cancer, because their friends have just been struck down by it. Colonoscopy could definitely exclude this cancer if the examination is negative. This would greatly allay their fear and anxiety. If polyps are present, they are removed straight away. As nearly all colorectal cancers are developed from benign polyps, their removal prevents cancer.
Because colorectal cancer is so common, for the general population without any symptoms, it is sensible to adopt a proactive strategy to detect polyps and early cancer. Most cases of colorectal cancer appear after the age of 50 for both men and women. It is reasonable to start screening from age 50. |
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If one has a family history of colorectal cancer, polyp or related breast and uterine cancers, screening might start earlier. The age to start screening depends on individual risk profile.
Colonoscopy can only be properly performed in a clean colon. Therefore, patients must take strong laxatives to purge the bowel starting the evening before the procedure. It is performed under sedation with very careful monitoring to ensure it is as safe as possible.
The process usually takes 15 to 20 minutes and it is painless.
Colorectal Surgeon, Dr Goh Hak Su explains:” Colonoscopy is safe but like all procedures it has risks and complications. The most important complication is injury or perforation of the colon which requires emergency surgery. The overall risk is stated as 1:1000. But in experienced hands, this complicated is very rare indeed.”
Because of the risk of perforation, virtual colonoscopy or CT colonography is sometimes advocated. The patient is given an injection of contrast, pumped with air into the colon and put through a CT scan. The inside picture of the colon is reconstructed. Although it is good for visualisation of larger polyps and cancer, it cannot view flat lesions and is not sensitive for small polyps. However, its biggest drawback is when a patient has a positive virtual colonoscopy, he still needs to have a conventional colonoscopy for biopsy or polyp removal. Repeated CT scans have a risk of accumulated radiation which itself can cause cancer.
How often should one go for a colonoscopy?
For an individual with average risk, every five years is sufficient. However, for those with a history of polyps or cancer, once every three years is recommended. For some rare individuals with a high risk of colorectal cancer because of abnormal genes, colonoscopy may be required yearly. |
