What Is Colonoscopy?
Colonoscopy is a procedure for diagnosing and treating a variety of problems encountered in the colon (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. Abnormalities which are too small to be seen on x-ray may also be identified and colonoscopy is now considered to be a more accurate examination of the large bowel than barium enema x-ray.
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 polypectomy. This is achieved by passing a wire loop through the colonoscope and snaring the base of the polyp, which is then severed from its attachment to the bowel wall by means of an 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 colon cancer, (one of the most common cancers in Australia). 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 preparation 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 (distension) 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 60 minutes especially if polyps are to be removed.
What Happens After Colonoscopy?
You will be asked to rest for a 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 should not drive yourself home after your colonoscopy. You should therefore 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 a very low risk of complications, although these occur very occasionally.
Localized irritation of the arm vein may occur at the site of injections of the sedatives. A lump may develop and remains for several weeks or even months, it will eventually disappear.
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.
The colonoscope was developed in Japan in the 1960's and was preceded by instruments used to examine the stomach.
The first flexible instrument was the gastrocamera and later the gastroscope. The gastroscope was subsequently modified to examine the large bowel (colonoscope).
Colonoscopy was first used in Australia in the early 1970's and many technical (and expensive) improvments have occurred since. The image of the bowel interior is now observed on a video screen which allows all members of the colonoscopy team to assist more appropriately.
The technique of Colonoscopy is difficult to master and strict guidelines for training now exist to ensure expertise and safety.