COLONOSCOPY - a patient's guide
What is it?
Colonoscopy is a technique developed to investigate and treat disorders of the rectum, colon (large bowel) and the lower end of the ileum (small bowel). The instrument used is known as a colonoscope and consists of a flexible tube with a minute video camera at the end. The tip of the instrument can be guided using controls and samples can be taken through a channel, which passes the full length of the colonoscope. It is also possible to remove small colon growths called polyps during the procedure. Because direct viewing is possible, and samples can be taken for microscopic examination, colonoscopy is the most accurate method currently available for examining the inside of the colon.
When is a colonoscopy required?
Colonoscopy can be used both for investigating symptoms and for screening people who are asymptomatic but are at increased risk of diseases such as colon cancer. The usual indications for colonoscopy include:
- Bleeding from the rectum
- Unexplained anaemia
- Inflammation of the bowel lining
- A change in bowel function such as diarrhoea or constipation
- Unexplained abdominal pain
- A strong family history of bowel cancer (see article on colon cancer)
- Previous polyps (growths) (see article on polyps)
- Follow-up after previous removal of bowel cancer or polyps
How do I know if I need a colonoscopy?
The best person to advise you is your family doctor. If they feel you need a colonoscopy you will be referred to a specialist surgeon or gastroenterologist who performs colonoscopy.
What happens before the colonoscopy?
Before preparing for a colonscopy it is very important that any potential risks are identified. Your doctor will want to know if you have any major medical disorders such as:
- Asthma or other lung disorders
- Bleeding disorders
- Heart conditions
- Previous surgery
- Medications such as warfarin, lithium or insulin.
- Allergies to any medications
To allow an adequate view, and for safety purposes, the bowel needs to be cleared adequately before colonoscopy. The day before the investigation you are advised to drink large volumes of clear fluids. Solid food should be avoided. You will also be given a combination of laxatives (e.g. Dulcolax) and a liquid, such a "Fleet," to drink. This will cause diarrhoea and it is important you maintain an adequate fluid intake to prevent dehydration. Some people experience vomiting and this can be controlled using medications such as Maxolon.
What does the examination involve?
Usually the examination is performed on an outpatient basis. The procedure will be explained to you again and you will be asked for written consent. Colonoscopy takes approximately half an hour but you should allow at least 2 hours as a recovery period is needed before going home. You will need to change into a gown to protect your clothing. Initially you will be positioned on your back and the turned onto your left side.
Normally intravenous sedation is given to relieve any discomfort. Some people choose not to have sedation and occasionally a general anaesthetic is chosen. If sedation is used a small needle in the back of the hand is all that is required. You will probably not be unconscious but your recollection of the procedure will be poor due to the medication. This effect can extend to the period after the procedure as well. For this reason it is often necessary to return for a further visit to discuss the results of the investigation and the outcome of any biopsies taken from the bowel.
Sedation can impair your judgement for up to 24 hours afterwards. It is illegal to drive while still under the influence of sedation and you will need to arrange for alternative transport such as a lift from a family member or friend. You should also not make any important decisions or sign any documents during this period.
The instrument is inserted through the anus and passed right around the colon to the area of the appendix. This is not normally painful but it can be uncomfortable particularly when corners are passed. Distending the colon with air can also cause discomfort. If necessary, pain-relieving injections can be given during the procedure via the needle in your hand. Most endoscopists use video equipment now and if you are interested you may be able to watch the screen. If any polyps are seen they will normally be removed. Electric current is used to burn the base of the polyp to prevent bleeding.
What happens after the procedure?
You may have some remaining ache following the procedure that can last a few hours. If this is severe or is increasing you should notify the person who performed the procedure, if possible or your own family doctor. A small amount of bleeding can occur after samples are taken but if this is more that half a cup you should also contact the appropriate doctor.
What complications can occur?
Complications are rare when colonoscopy is performed by an experienced endoscopist, but there are some potential risks you need to be aware of:
- Drug reaction
Complications are more frequent when the bowel is diseased particularly when there is inflammation, diverticular disease, narrowing or cancer. Interventions, such as taking out polyps (polypectomy), also increase the risk of complications particularly bleeding and perforation. Diabetics, who take oral agents or insulin, may develop low blood sugar when starved. Certain mediations, for example warfarin and aspirin, can cause increased bleeding. For every 10,000 people having a colonoscopy, approximately 2 will die as a result of complications (see below).
The following figures give average published risks for complications or death following colonoscopy:
Diagnostic colonscopy has a major complication rate of 0.4% and a death rate of 0.02%. Polypectomy has a major complication rate of 2.0% and a death rate of 0.05%.
These risks will be discussed with you before the procedure and only when the indications for the procedure outweigh them will colonoscopy be advised.
Colonoscopy is now a very common procedure, which allows treatment as well as diagnosis. While it is very safe there are risks that you should be aware of. These risks are generally compensated for by the benefits of an accurate diagnosis allowing appropriate treatment of the underlying condition. You are encouraged to discuss this procedure further with your family doctor.