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What is a Colonoscopy?

A colonoscopy is a procedure that is done to thoroughly examine the lining of the colon and rectum. It is a long flexible tube that is inserted via the anus and is advanced along the rectum and colon until it reaches the beginning of the colon.


Why do I Need a Colonoscopy?

Your doctor may recommend an examination if you have symptoms suggesting possible problems in the colon or rectum. Some symptoms include bleeding, change in your bowel habits, unexplained abdominal symptoms. It is also used to monitor patients with inflammatory bowel disease, and for follow-up of patients with history of colon cancer or polyp. It is also recommended to have a colonoscopy screening at the age of 50 years (younger if you have any family history of colorectal cancer).

A colonoscopy can effectively keep colorectal cancer at bay.
If you are in a higher-risk group, speak to your doctor to determine an appropriate screening schedule.

What Needs to be Done before Going for a Colonoscopy?

For colonoscopy and all other forms of examination of the colon, it is important to clear the colon of stools. Patients are asked to take very potent laxatives to clear the colon. In most cases, if the procedure is to be done in the morning, you will be asked to take the laxatives and purge the night before. If the procedure is to be done in the afternoon, you will be asked to clear the bowels in the morning of the examination.

You will be encouraged to drink as much fluid as possible while you are clearing the bowel. You are also discouraged to take high fibre food such as vegetables and fruits 1 day prior the examination.

For patients who are on aspirin or other blood thinning medications, your colorectal surgeon will advise you on when you should stop those medications. After taking the medication to clean your colon, expect to make multiple trips to the toilet. A lot of people have expressed that this is the worst part of the entire procedure.

What to Expect on the Day of the Colonoscopy?

Relax. The worst part is already over.

Most people are fearful of colonoscopy because they feel that it is a very invasive procedure and are concerned about pain. Most patients do not feel any pain or even remember about the procedure after the they wake up from sedation.

On the day of the procedure, go to the Endoscopy Centre about 30 mins to one hour ahead of your appointment time. This is to give yourself some time to go to the toilet one last time should you need to and not feel so rushed.

Your doctor will likely give you a sedative by injection though some patients may want to watch the procedure "live" and want to do the entire procedure awake. This is possible as the procedure makes most people feel bloated and have the urge to pass motion rather than actual pain.

After you are asleep, your doctor will insert the colonoscope via the anus and advance it up the rectum and along the colon. The scope goes up along the left side of the abdominal cavity until it reaches just below the ribcage. It then makes a turn and goes across to the right side, before finally going downwards to the right lower part to the abdomen. The end of the colon is recognized as such due to the presence of the appendix opening and the opening of the small intestines into the colon (the ileocaecal valve). In certain conditions where it is indicated, your doctor will advance the scope through the ileocaecal valve to inspect the last part of the ileum.

One of the main advantages of colonoscopy over other methods of colon examination is that it allows direct visualization rather than rely on indirect imaging techniques. It also allows any adherent stools to be washed away to see the colon lining beneath. It is also the only technique that allows to tissues to be removed for biopsies and for polyps to be removed.

What to Expect after?

Most people do not have any side effects after the procedure. Some people may feel bloated because of residual air left in the colon. Do remember that it is normal to have less bowel movement the next few days because a lot of stools have already been cleared out by the bowel preparation.

In the hands of an experienced specialist, a colonoscopy is a very safe, accurate and painless screening procedure.

What are the Risks of the Procedure?

The most serious complication that can occur is that of colonic perforation. The risk is less than 1 in 1000 or 0.1%. Perforation means break in the wall of the colon. This may be caused by direct trauma of the colonoscope pushing and causing a tear in the colon wall. In some cases, there is a delay perforation after removal of a polyp. This is usually due to thermal injury at the time of polyp removal or when the cut is too deep into the wall of the colon. If perforation happens, surgery is usually required to rectify it, though there are now new but unproven techniques to try to close the hole through the colonoscope.

I am Still Scared. Are There Other Ways to Examine the Colon?

There are two other methods to examine the colon: barium enema and computer tomography (CT) colonography (also known as virtual colonoscopy).

It is important to remember that whatever the technique used, the colon still has to be cleared of the stools to ensure an accurate examination. The medications given for the different tests may differ but the end result, purging, is still the same.

Barium enema is performed by a radiologist who first inserts a tube through the anus. A bag of white liquid (barium) is then poured into the colon through the tube. The patient is rotated so that the barium can flow around the colon. The bag is then dropped to the floor and the barium allowed to flow out. Air is then pumped in through the tube to distend the colon and x-ray images are taken with the patient in different positions.

There is no sedation given for barium enema.

The other available technique to examine the colon is CT colonography or virtual colonoscopy. At the time of the investigation, the radiologist will insert a tube into the rectum via the anus. One to 1.5 litres of air will be pumped in to inflate and distend the colon. The patient will lie down on his back in the CT scanner, an intravenous injection given and the scan will be done. The patient will then lie prone on his tummy and the process repeated. The virtual image of the colon is then produced using computer software.

One of the reasons patients opt for barium enema or CT colonography is because they perceive colonoscopy to be more invasive and has higher risk of complication, especially perforation. The reported risks of colonoscopy perforation is less than 0.1% and in the hands of a skilled endoscopist it is much lower. Barium enema and CT colonoscopy also have a risk of perforation in the region of 0.05%.

It is also important to remember that if there are polyps or suspicious lesions detected on barium enema or CT colonography, it would be required to remove the polyp or for biopsy of the lesion.

To learn more about colonoscopy, visit our dedicated website -- Colonoscopy Clinic in Singapore.
Read on for More Information on Colorectal Cancer:
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Our Colorectal Cancer Surgeon
Ho Kok Sun Colorectal clinic logo
Dr Ho Kok Sun
Colorectal & General Surgeon
MBBS (Singapore),
M Med (Gen Surg) (Singapore),
FRCSEd (Gen Surg), FAMS
Dr Ho Kok Sun has been committed to treating colorectal cancer for over a decade. This includes preventive care through providing colonoscopy in Singapore. He was the past President of the ASEAN Society of Colorectal Surgeons and the Society of Colorectal Surgeons (Singapore), as well as a founding member of the Eurasian Colorectal Technologies Association. Dr Ho was actively involved in the training of medical students and residents, and has published widely in reputable journals and book chapters. He believes that treatment should always be personalised to the patient’s needs.

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Ho Kok Sun Colorectal

Colorectal Surgeon

3 Mount Elizabeth,
Mount Elizabeth Medical Centre
#04-08, Singapore 228510

Tel (+65) 6737 2778
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