About Colonoscopy Examinations

What is a Colonoscopy?

Colonoscopy is an examination of the lining of the colon (large bowel).

The colonoscope is a long, flexible tube with a tiny video camera on the end (and thousands of tiny glass fibres to transmit light to the tip). It is passed through the anus and around the colon. The lining of the colon can be directly visualised on a video screen. If polyps are seen, they can usually be removed during the examination. The colon is also checked for other abnormalities such as the presence of blood, narrowings, diverticula (pockets) or inflammation. Colonoscopy is the most accurate way of examining the inside of the colon.

A colonoscopy examination may be recommended:

  1. To look for causes of blood loss from the bowel.
  2. To determine the extent and severity of inflammation of the colon.
  3. To check for polyps.
  4. To re-examine the colon after a polyp, or cancer, has been removed and to check that no new growths have developed.

What is a Polyp?

A polyp is a mass or lump on the wall of the colon. It is an overgrowth of glandular cells in the lining of the colon. Adenomatous polyps have the potential to turn cancerous. It takes a period of years for a polyp to turn into a cancer.

The cause of polyps is unknown. If your family members have had polyps, or colorectal cancer, your risk of developing the disease is higher. If you have had a polyp or cancer in the past, you are more at risk of developing future polyps or cancer. Research suggests that polyps and colorectal cancers are less likely to occur if you have a diet high in fibre and calcium and low in animal fats. When a polyp is found, it should be removed and examined by a Pathologist. When one polyp is found there is a 40% chance there will be others present in the bowel so it is important to examine the entire colon.

Preparation for Colonoscopy

It is most important that the bowel is completely clean. The cleaner the bowel, the easier and more thorough the examination will be. The day before the examination a liquid diet with plenty of fluids is recommended. Follow your bowel preparation form carefully. You will usually be required to take a combination of laxatives the day of or prior to the examination.

Please notify the nurse at the Rooms of any allergies, if you have any artificial joints, an artificial heart valve, if you are on Warfarin or other blood thinners (e.g. aspirin, clopidigrel, dabigitran), Lithium or a Diabetic.

The Examination

The examination is usually carried out on an outpatient basis in our Christchurch clinic. It is not normally a painful procedure, however, some discomfort may be felt when air is introduced into the bowel or when the colonoscope is gently manoeuvred around the corners of the bowel. The procedure usually lasts about 30 minutes. You will be positioned on your left side for the examination.

A light sedative will be given to you prior to commencement of the examination. This is given through a vein and will help control any discomfort during the examination. It is not compulsory and you may choose not to have sedation. Pain relief medication is also given via this route.

About Sedation

At the completion of the examination you will be taken to the recovery ward for a period of rest and observation. The usual recovery time is about one hour (recovery time may vary). It will be necessary for you to arrange for someone to collect you from Reception to drive you home. It is illegal to drive yourself following sedation.

You are welcome to bring a support person to your hospital and rooms visits if you feel they would be of assistance to you.

The results of the colonoscopy will be reviewed with you at the completion of the procedure and you will be given a written report. You may have a hazy memory of the period during and just after the examination. If you have any questions about the colonoscopy please do not hesitate to call us for a report. If a polyp or biopsy has been taken it will be sent to the laboratory and a report is usually available within 3-4 days. A copy of this report is sent to your GP also.

There may be a small amount of blood in the bowel movements for up to 4-5 days after the examination. If bleeding seems excessive, or you have any questions, please contact us. It is not uncommon to experience abdominal discomfort after the procedure which is caused by air being introduced in to the colon. We advise patients to pass wind as required to lessen abdominal griping. Paracetamol may be taken during this time.


Complications are rare. However, as with any diagnostic procedure, there are potential risk factors to be considered.

  1. Bleeding – this can occur with any type of biopsy.
  2. Perforation of the bowel – this may require surgical intervention.
  3. Over-looked pathology – no investigation is 100% accurate although colonoscopy comes very close. There is a small chance that a tiny polyp may be missed.
  4. Incident cancers – very rarely a cancer will develop in the period before your next colonoscopy (if a recall is indicated).

Incomplete Examinations

If for some reason the colonoscopy is unable to be completed (due to discomfort, anatomy or poor preparation) you may be asked to have an additional investigation to complete the examination. This may be a CT scan (called a CT colonography). It will be arranged for you at the time of your admission and will be done on the same day to ensure you do not need to go through a second bowel preparation. This investigation is usually done at St Georges Radiology in Christchurch. There will be a separate fee for this investigation which will be charged from the Radiology Rooms (please call them on 03 379 0770 for an estimate for the price of this investigation).

Follow up

If you have a polyp you are in a high risk group and more likely to develop additional polyps. After a polyp is removed you are advised to have your colon examined again at regular intervals. This is called surveillance screening.

Information Sheets

Bowel preparation sheet for morning colonoscopy

Bowel preparation sheet for afternoon colonoscopy

Dried Fruit Fibre Supplement for Constipation