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Information about Colonoscopy


What is a colonoscopy?

Colonoscopy is a very useful procedure that examines your large bowel (colon). A long thin flexible tube with a camera at the tip is passed through the rectum into the colon. Pictures from the camera are seen on a television screen by the endoscopist. The procedure usually takes approximately 30 minutes and is done under conscious sedation.

The following video made by Southland Hospital explains the procedure in detail, but please note that some details differ between Southland and Hutt Valley:

Why have a colonoscopy?

Colonoscopy is used to investigate symptoms you have been having, for example a change in bowel habit, rectal bleeding, or abdominal pain. Your doctor may want to review a chronic condition such as colitis or check for recurrence of polyps. A colonoscopy can also be used to check for bowel cancer.

How do I prepare for colonoscopy?

For a successful colonoscopy it is essential to empty the bowel thoroughly of all waste material. This is done by taking a bowel preparation that works as a powerful laxative. It is very important that the preparation works so that the doctor is able to see clearly inside the colon. Please follow the instruction sheet carefully. Failure to follow these instructions may result in an unsuccessful procedure and you may have to return for a repeat procedure.

A complete bowel preparation will be discussed at your pre-assessment with the nurse, which will generally be by telephone.

Patients should also inform the nurse of all medical conditions, particularly diabetes or sleep apnoea.

If you are taking medications, especially blood thinning medication such as warfarin, or iron tablets, please let us know as sometimes these medications need to be stopped a few days before the procedure.

Women taking the oral contraceptive pill should be aware that taking bowel preparation might prevent the pill from working.

How is colonoscopy performed?


Before the procedure begins a sedative is usually given – you will not receive a full general anaesthetic, which means you will not be completely unconscious. You may be slightly aware of what is going on in the room, but generally you won’t remember anything. The doctor and nursing staff monitor your vital signs during the procedure and will attempt to make you as comfortable as possible.

Examination of the bowel

Once sedated and lying in a comfortable position on your left side, the doctor inserts the flexible colonoscope (‘scope’) through the rectum and slowly guides it into the colon. The small camera in the end of the scope transmits a video image to a monitor, allowing the doctor to carefully examine the intestinal lining.

Once the scope has reached the opening to the small intestine, it is slowly withdrawn and the lining of the large intestine is carefully examined again on the way out.

The endoscopist introduces air into the bowel via the endoscope so you may experience bloating from the air and cramp-like pain as the camera goes around the bend of the bowel.

You may also be asked to change your positon i.e. roll onto your back during the procedure.

Removal of polyps and biopsy

A polyp is a small tissue growth attached to the bowel wall. These are common in adults and are usually harmless, however, most colorectal cancer begins as a polyp so removing them early is an effective way to prevent cancer.

If polyps are found during the procedure they will usually be removed there and then using tiny tools passed through the scope. Small tissue samples (‘biopsies’) of the bowel may also be taken. All polyp and tissue biopsies are sent to the laboratory for testing.

Are there any risks or side-effects?

Although complications can occur, they are rare and will be discussed with you prior to the procedure taking place.

  • Having a colonoscopy carries a small risk of making a hole in the bowel wall (perforation). This occurs on average no more than once in every 1000 examinations. Perforations usually need to be repaired with an operation.
  • If a polyp is removed then the risk of perforation, although still rare, increases slightly to 1 in 500 occasions.
  • Bleeding from the back passage can occur, especially if biopsies are taken or polyps removed. Bleeding usually stops without any treatment, but occasionally treatment is needed to stop this.
  • Using sedation can affect your breathing. Your breathing is monitored by staff during the procedure. The endoscopist may give you less sedation if it is felt that you are at high risk of breathing difficulties during the procedure.
  • Despite sedation some patients experience abdominal discomfort or pain due to the air that is put into the bowel via the endoscope or due to the scope negotiating the natural bends in the bowel. This should decrease when the procedure has ended and will be helped by passing wind.

Occasionally, people may be intolerant to the bowel preparation medication and experience headaches or vomiting.

What happens after colonoscopy?

Following the procedure you will remain in the recovery area until the sedation wears off. You will usually be given something light to eat or drink once you are awake.

You should expect to be with us for approximately 4 hours in total.

When you wake up you may feel a little bloated. This is due to the air that was inserted during the procedure and will pass over the next hour or so. Bloating may last longer but should clear within 24-48 hours.

In most circumstances your doctor will briefly inform you of your test results on the day of the procedure. The result of any biopsies or samples taken can take 1-2 weeks to be processed, so your results will be discussed with you by your GP or specialist.

Who can I contact if I have any questions?

You will be given an opportunity to ask questions at the time of your pre-assessment and again prior to your procedure when you are asked to sign the consent form.

If you have any problem understanding or reading any of this information, please contact the Endoscopy Unit staff on 570 9191.