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Your step-by-step guide to Colonoscopy

  Thursday, 26 l 05 l 2011  Source: Mind Your Body; The Straits Times   
By: Ng Wan Ching


Three categories of patients should be screened.

  • Those at very high risk – those with a family history of hereditary colon cancer.
  • Those at high risk – those in the family with a first-degree relative (parent, child or sibling) with colon cancer, especially when this relative was younger than 60 years old at diagnosis.
  • Those at average risk – those who are 50 years old or older. Most people will fall into this group, which the Ministry of Health is targeting.


The screening for the first two groups is colonoscopy, a visual examination of the colon and rectum through a scope. Those who are at average risk have the choice of taking the faecal occult blood test, computed tomography (CT) colonography, barium enema or colonoscopy.

The faecal occult blood test looks for blood in the stools. CT colonography is a medical imaging procedure which uses X-rays and computers to produce two- and three-dimensional images of the large intestine from the lowest part, the rectum, to the lower end of the small intestine.

In a barium enema test, the doctor fills the colon with a contrast material, barium, through the rectum and takes an X-ray of the abdomen.

The choice of the test will have to be worked out with the individual as the accuracy, cost and level of the individual’s involvement varies. The blood test is the easiest but the least accurate.

Colonoscopy is arguably the most accurate and offers the opportunity for immediate removal of polyps, the precursors to cancer. However, it is more involved, requiring a day off work and preparation to cleanse the colon. It also carries risks of bleeding and perforation during the procedure. As it is so accurate, it needs to be considered only once every 10 years if the first one is normal, unlike the blood test, which should be done annually. The blood test detects only cancer and larger polyps that bleed and not smaller polyps in the pre-cancerous stage. A positive result requires follow-up colonoscopy.

Associate Professor Tang Choong Leong, who heads colorectal surgery at Singapore General Hospital, said: “However, if after normal colonoscopy, you develop symptoms such as blood in the stools or a change in your bowel habits, you should come in for colonoscopy again.”


You need to cleanse your bowels either the day before or on the morning of the colonoscopy. A lavage solution (an isotonic salt solution) has to be consumed in a specified time of two to three hours. This will result in watery loose stools or just plain water being passed out at the end of the preparation so that the inside of the colon is clean for direct inspection using the colonoscope. There is no pain involved in the preparation.


Most patients are sedated during the procedure with a short-acting tranquilliser injected intravenously. Some may choose to undergo the procedure awake. Most experience bloating, distension and occasionally spasms if the scope traverses a bend or twist in the colon. A fibre-optic tube, the thickness of an index finger, is introduced through the anus and the surgeon will pass it up the large intestines all the way to the beginning, the caecum. The colon is inspected twice – during insertion and also during withdrawal of the tube.

If a polyp is detected and is small and safe enough to be removed immediately, then forceps or a wire loop is inserted through a channel in the scope to grip, cut and remove the polyp. Bleeding is stopped by an electric current. This is entirely painless even if the person is awake and watching.

The colonoscopy and polyp removal take more than 10 minutes, depending on the degree of natural twisting in the colon, the cleanliness of the preparation, and the number, size and location of the polyps that can be removed. Provisional findings are known immediately and the discharging nurse will usually inform the patient of the results before he or she leaves. The removed polyps may be sent for further testing. In this case, the results will be reviewed at a follow-up visit one to two weeks later.


polypAnything that looks abnormal. Doctors may perform a biopsy on larger polyps that cannot be removed through the scope. This means a pair of small forceps is passed down the scope to pinch a small sample for testing.


Colonoscopy carries a risk of bleeding and perforation, especially with the removal of polyps, in the region of eight per 1,000 procedures carried out and one per 1,000 respectively. Most bleeding is minor and stops spontaneously. In severe and persistent cases, repeat colonoscopy may be needed or even surgery to stop the bleeding. Most perforations would require surgery for repair.


Most hospitals here carry out this procedure. With subsidies, the average bill for colonoscopy can cost between $300 and $700. Without subsidies, it is at least $1,000. The cost varies depending on the seniority of the doctor doing the procedure and if other tests are required. The Medisave withdrawal limit will be pegged at the prevailing withdrawal limit for day surgery procedures, at $950 for colonoscopy and $300 per day for associated daily hospital charges. It is applicable only for colonoscopy done in Singapore. The list of institutions approved to carry out the procedure for which Medisave can be used will be out closer to July 1.

Source: Associate Professor Tang Choong Leong, head of colorectal surgery at Singapore General  Hospital, and Ministry of Health.

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