Summary points:

• Colonoscopy is a test procedure used to examine the inside the colon and rectum.
• The test requires adequate cleansing of the colon for optimum visualization of the inner lining which is usually achieved through a combination of dietary change and drinking a bowel preparation kit.
• Patient comfort during the procedure is achieved by providing a light sedation with medications.
• The doctor may take biopsies of the abnormal looking areas for diagnostic purposes and in most occasions will remove polyps.
• Driving is not permitted for 24 hours after a colonoscopy to allow the sedative time to wear off.

What is colonoscopy?

A colonoscopy is a procedural test which comprises examination of large bowel (colon) and lower most part of small bowel via use of a long and thin flexible tube with a video camera attached to the tip. The tube is inserted through the back passage and is advanced to the terminal ileum (lower most part of small bowel) and allows the doctor to examine the large bowel to diagnose many conditions and also to perform specialised procedures such as taking biopsies for pathology and removal of polyps (abnormal growths which sometimes develop into cancer).

Why you may need a colonoscopy?

You may need a colonoscopy to screen for bowel cancer in certain situations such as a relative with diagnosis of bowel cancer, a family history of polyposis syndrome, a positive National Bowel Cancer Screening stool test etc. Colonoscopy can detect inflamed tissues, polyps and cancers, such as colorectal cancer. It can help doctors diagnose unexplained changes in bowel habits, abdominal pain, bleeding from the bowel and weight loss.

What preparation is required before colonoscopy?

A thoroughly cleansed bowel is a prerequisite for adequate colonoscopy examination. This is achieved by drinking a bowel preparation that will cause diarrhoea and emptying of the bowel. Failure to achieve adequate bowel cleansing may mean a need to return for a repeat procedure. A complete bowel preparation consists of:

1. Changing the diet for a few days prior

A low fibre diet is followed for a few days prior to procedure to minimise the waste material in the colon. In addition, seeds and grains need to be avoided for several days before the procedure because they can block the suction channel of the instrument.

2. Drinking bowel preparation

Bowel preparation, also called bowel prep, is a combination of laxatives that cause diarrhoea and empty the colon. Depending on your medical condition, your doctor will recommend the right one for you.

3. Increasing your fluid intake

4. Medication adjustment

Specific and detailed instructions will be given to you prior to procedure. While you can keep taking most medications as usual (with a few sips of water), certain other medications may need adjustment of dose and/or timing and occasionally temporary suspension particularly blood thinners and diabetic medications including insulin. Let us know if you are on blood thinners or diabetes medications.

How is colonoscopy performed?

Deep sedation is usually given prior to procedure. The doctor and medical staff will monitor your breathing, pulse and blood pressure during the procedure and will make you comfortable. You may be vaguely aware of proceedings in the endoscopy room but will generally not remember anything. Once you are sedated and lying on your left side, the doctor passes the instrument through the anus and into the colon. A small camera in the end of the scope transmits a video image to a monitor, allowing the doctor to examine the intestinal lining. Once the scope has reached the point where the small intestine joins the colon, it is withdrawn carefully and the lining of the colon is examined again. A colonoscopy usually takes between 20 and 45 minutes, but can take longer depending on the abnormalities found and treatment required.

Quite frequently, biopsy samples to diagnose microscopic signs of disease and polyp removal will be performed during colonoscopy. A polyp is a small tissue growth on the bowel wall. They are common and are usually harmless, but a small proportion of them will develop into cancer. Removing them is an effective way of preventing cancer. After the procedure is completed, you will be monitored in the recovery area for an hour or two until the sedation wears off. You will usually be given something to eat and drink once you are fully awake.

You may feel a little bloated due to the air that is used to inflate the colon to allow adequate inspection of the lining. It generally passes within an hour or two. Rarely you may pass a small amount of blood. This is often due to the samples that have been taken and should settle. Because of the sedation given during the procedure, it is very important that you do not drive a car, travel on public transport alone, operate machinery, sign legal documents or drink alcohol on the day of the colonoscopy. It is strongly advised that a friend or relative takes you home and stays with you. Full recovery is expected by the next day. It is important to read your discharge instructions carefully.

Are there any risks or side effects?

Although complications can occur, they are rare when the procedure is performed by doctors who are specially trained in colonoscopy. Very few people experience serious side effects from colonoscopy and polypectomy (polyp removal). The chance of complications depends on the exact procedure that is being performed and other factors including your general health. Very rarely (one in 1,000 cases), the bowel lining may sustain a tear; if this occurs you will be admitted to hospital for an observation, bowel rest, antibiotics and occasionally an operation to repair the lining may be required. Occasionally, people may react to the bowel preparation medication and experience headaches or vomiting. Reactions to the medications used for sedation are also possible, but again rare.

In a few cases, if the colonoscopy is not successfully completed it may need to be repeated. If you have any of the following symptoms up to 14 days after the colonoscopy you should contact the hospital or your doctor’s rooms immediately:

• Fever
• Any symptom that concerns you
• Severe abdominal pain
• Black, tarry poo
• Persistent bleeding from the anus

How accurate is a colonoscopy?

Colonoscopy is the most accurate test for examining the colon but is not perfect and there is a small risk that an abnormality may not be detected. A colonoscopy can miss small polyps in the bowel in 2 to 8 per cent of cases. For bigger abnormalities such as cancer, the chance is much less, but still present. For these reasons, it is recommended that all patients over the age of 50, and those with a family history of colorectal cancer, perform a faecal occult blood (FOB) test every one to two years and/or participate in the National Bowel Cancer Screening Program. The FOB test kits are available from your chemist or local doctor.