What is Colonoscopy?
Colonoscopy is a procedure for diagnosing and treating a variety of problems encountered in the colon and rectum (also called the large bowel or large intestine). It is performed using an instrument called a colonoscope which is a flexible tube that is about the thickness of a finger. It is inserted via the rectum into the colon and allows the doctor to carefully examine the lining of the bowel.
Abnormalities suspected by x-rays can be confirmed and studied in detail. If the doctor sees a suspicious area or needs to evaluate an area of inflammation in greater detail, he can pass an instrument through the colonoscope and take a piece of tissue (a biopsy) for examination in the laboratory. Biopsies are taken for many reasons and do not necessarily mean that a cancer is suspected.
What is Polypectomy?
Sometimes colonoscopy is undertaken to locate or remove polyps. These are small growths on the lining of the bowel. They are usually benign but occasionally can contain a small area of cancer. Removal of a polyp is called a polypectomy. This is achieved by passing a wire hoop through the colonoscope and snaring the base of the polyp, which is then severed from its attachment to the bowel wall by means of electric current. This current cannot be felt and causes no pain.
Early detection and removal of polyps prevents them from becoming malignant, and is therefore an important means of protection from colorectal cancer (one of the most common cancers in Australia and New Zealand). The ability to remove polyps with the colonoscope means that the patient can avoid a major operation. After colonoscopic polypectomy the patient is allowed to resume usual activities within a day or two, and can return to a normal diet almost immediately.
Is Any Special Preparation Necessary?
Yes. For a successful colonoscopy, it is essential that the bowel is thoroughly emptied. This will usually mean taking clear liquids as well as a special laxative before the colonoscopy. More specific instructions will be given to you. Occasionally one or more enemas may also be required. This preparation can usually be done at home. Failure to carry out the full preparation may leave solid material in the colon and could prolong the procedure or necessitate a repeat examination at another time.
What Happens During Colonoscopy?
When you arrive for the colonoscopy you will be asked to change clothes and may be given a small enema. The examination may be performed with intravenous sedation or a light anaesthetic and your particular management will be explained to you.
If you are being managed with sedation you will probably sleep during most of the procedure but you may be aware of changes in position, inflation of the colon with air (distention) and temporary abdominal discomfort. Examination of the large bowel lining is made as the instrument is being inserted, and again as it is withdrawn.
The examination may take up to 60 minutes especially if polyps are removed.
What Happens After Colonoscopy?
You will be asked to rest for an hour or two until the effects of the sedatives have worn off, and you have passed much of the inflated air. Although most of the effects of the sedative/anaesthetic wear off quickly you must not drive yourself home after your colonoscopy. You must arrange for a friend or relative to accompany you when you leave.
Are There Any Complications From Colonoscopy or Polypectomy?
Colonoscopy and polypectomy are very safe procedures with very low risk of complications, although these occur very occasionally. Depression of breathing may occur with sedation and to prevent this, the oxygen level in the blood is monitored during the procedure. Although colonoscopy is the most accurate test there is for detecting bowel cancer, there is still a small risk of missing a cancer.
Bleeding may occur from the site of the biopsy or polyp removal. It is usually minor and stops on its own, or can be controlled by cautery through the colonoscope. Very rarely transfusions or surgery may be required.
Perforation of the colon rarely occurs during colonoscopy however this can require abdominal surgery to close the defect in the bowel wall. Great care is taken to avoid this complication.