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HealthInfo West Coast-Te Tai Poutini


Your surgeon has determined that you need a colonoscopy for further evaluation or treatment of your condition. This information sheet should help you understand the procedure. It includes answers to the questions that people most frequently ask.

Please read the information sheet carefully. If you have any other questions, please feel free to discuss them with the endoscopy nurse or your surgeon before the examination begins.

What is a colonoscopy?

A colonoscopy is a procedure that lets your surgeon check the lining of your colon (large bowel) for abnormalities. This is done by inserting an endoscope through your rectum and advancing it slowly around your large bowel. An endoscope is a thin flexible tube that allows the surgeon to see inside your bowel.

A flexible sigmoidoscopy is similar to a colonoscopy, but it only examines the lower part of the colon, while a colonoscopy examines the whole large bowel.

What preparation is required?

Your colon must be completely clean for the procedure to be accurate and complete. Your appointment letter includes instructions about where to pick up the bowel preparation you need to take beforehand. You should pick up the bowel preparation at least one week before your procedure.

Please follow the instructions carefully. You may experience diarrhoea overnight before the examination but this is normal.

What about my current medications?

You can take most medications as usual, but some can interfere with your preparation or the examination.

What can I expect during colonoscopy?

You will normally be given a sedative for pain relief and to relax you so that you may have little or no memory of the examination. Without the sedative you could experience abdominal discomfort. A few people request little or no medication. If that is what you want, please let us know at the time of the examination.

There is often a feeling of pressure, bloating, or cramping at times during the procedure. The examination itself will usually be over within 30 minutes, although sometimes it takes longer.

90% of people are able to have the whole of their large bowel examined, so the aim of the examination is achieved for most people.

What if the colonoscopy shows something abnormal?

If your surgeon thinks an area of the bowel needs to be evaluated in greater detail, an instrument will be passed through the colonoscope to obtain a biopsy (a sample of the colon lining). This is painless.

This specimen is sent to the Pathology Laboratory for analysis. Sometimes polyps or small mushroom-like growths are found which can be removed. This minor procedure, called a polypectomy, avoids an open abdominal examination. If polyps are found, they are removed because some can become cancerous.

What are the possible complications of colonoscopy?

Colonoscopy and polypectomy are generally safe when performed by surgeons who have been specially trained and are experienced in endoscopic procedures.

What happens after colonoscopy?


You need to arrange for someone to pick you up from the Brian Waterson Day Unit (1st floor, Grey Base Hospital) approximately two hours after the examination.

You should not be alone for the next 24 hours. Even if you feel alert after the procedure, your judgement and reflexes may be impaired by the sedation. Do not drive a vehicle, operate any machinery, drink alcohol, ride on public transport alone, sign any legal documents, or make any important decisions for 24 hours.

You may have some abdominal cramping or bloating because of the air introduced into the colon during the examination. This should disappear quickly with the passage of flatus (gas). Generally you should be able to eat and drink after your colonoscopy.

Further information

You have been given this information to prepare you for the procedure. If you have questions about your need for a colonoscopy or about other tests, do not hesitate to speak with your doctor. If you have any questions that have not been answered, please discuss them with the endoscopy nurse or surgeon before the examination begins. If you need any further explanation, please phone one of the following numbers:

Information provided by the Canterbury DHB. Adapted by the West Coast DHB. Last reviewed June 2017.

See also:

Colonoscopy & sigmoidoscopy if you have diabetes

Having an anaesthetic

Page reference: 75778

Review key: HICOL-20309