Colonoscopy

Colonoscopy is the endoscopic examination of the colon (large intestine) with a flexible, fibre-optic instrument, called colonoscope which is passed through the anus.

Colonoscopy is similar to but not the same as sigmoidoscopy. The difference being related to which parts of the colon each can examine. While colonoscopy allows an examination of the entire colon (measuring four to five feet in length), sigmoidoscopy allows doctors to view only the final two feet of the colon.

Colonoscopy allows removal of the polyps as small as one millimetre. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.

Reasons For Colonoscopy

Colonoscopy is performed for:

  • Colon cancer screening.
  • Positive FOBT.
  • Patients who have polyps.
  • Change in bowel habits
  • Anaemia, loss of appetite or weight without known reason.
  • Blood in the stools.
  • Ulcerative colitis and Crohn’s disease.
  • Chronic Diarrhoea
Preparation For Colonoscopy

The colon must be free of stool for colonoscopy to be performed properly. This involves bowel cleansing which is done prior to the colonoscopy. You will be given instructions on the bowel cleansing by the doctor and nurse.

Bowel cleansing involves taking a laxative preparation (e.g. phospho soda) followed by large quantity of fluid, preferably plain water or whole bowel irrigation using a solution of polyethylene glycol. If the bowel preparation is not completed before the colonoscopy and there is faecal matter in the colon, the procedure cannot be carried on and the colonoscopy has to be postponed.

If you are taking any long-term medication, especially blood thinners, warfarin, aspirin or diabetes medication, you should inform the doctor before the procedure.

How Is Colonoscopy performed?

After explaining the procedure, the nurse will help you to lie on the left side. The procedure is done under a light sedation to help you relax and better tolerate any discomfort.

After giving a sedation, the doctor will insert the colonoscope through the anus up the rectum, colon, and ultimately the terminal ileum, which is the end part of small bowel. During the procedure bowel is occasionally insufflated with air to maximize visibility. This might result in some bloating, cramping or pressure during the procedure, but this is usually well tolerated.

If necessary, tissue samples (biopsies) are taken during the colonoscopy and send for further analysis under the microscopy (histology). If a polyp (small growth of tissue that can develop into a cancer) is found in the colon, it can be removed during the colonoscopy. The entire procedure lasts about 15 to 30 minutes.

What Happens After Colonoscopy?

You will be observed at the Endoscopy Centre until the sedation has worn off, after which the doctor will explain you the result of colonoscopy and you will be discharged home.

Common after-effect from the procedure is a bout of flatulence and minor wind pain caused by air insufflation into the colon during the procedure. This will be relieved after you pass the gas. You will be able to eat normally the same day and resume your usual activities the next day. Do not drive or operate machinery till the next day, as the sedatives used will impair your reflexes.

What Are the Risks?

Colonoscopy is a very safe procedure. Complications are rare, but can occur. These include bleeding (0.1-2%) and bowel perforation (0.1-0.3%) (Ref. ASGE Guidelines). Bleeding can occur up to about two weeks after a colonoscopy especially if patient is taking aspirin or blood thinning medications. Rarely surgical treatment is needed. Some patients might have reactions to the sedation.

It is important to contact your doctor if you experience symptoms of severe abdominal pain, fever or rectal bleeding after colonoscopy.