Colonoscopy involves an endoscope (a thin flexible tube with a camera at the tip) being passed through the anus into the large intestine. It allows the doctor to inspect the large intestine for any abnormalities and also perform specialised procedures such as biopsies and removal of polyps. The very last part of small bowel (ileum) can also be investigated in this manner.
Colonoscopy is useful both for the diagnosis and treatment of different bowel conditions. It can help in the investigations of
unexplained changes in bowel habits,
abdominal pain,
bleeding from the bowel
weight loss.
diarrhoea
Positive National bowel cancer screening test (FOBT)
Colonoscopy is also done for treatment and removal of
colonic polyps
early colonic cancers (process called EMR)
What is a colonic polyp?
A polyp is a small tissue growth (like a wart) attached to the bowel wall. These are common in adults and are usually benign. Most colorectal cancer however begins as a polyp. For this reason it is advised that all polyps be removed at the time of colonoscopy using tiny tools passed through the scope as removing them early is an effective way to prevent cancer.
For a successful colonoscopy, it is essential to empty the bowels thoroughly. This can be done by taking a bowel preparation also called bowel prep. Failure to do this prior to colonoscopy may mean the doctor won’t be able to do a good examination, and you may have to return for repeat procedure.
Please see Bowel Preparation Information sheet on instruction on how to take bowel prep.
A light anaesthetic (twilight sedative) is used for the procedure. You will not receive a full general anaesthetic. You may be slightly aware of what is going on in the room, but generally you won’t remember anything. The back of your throat may be sprayed with local anaesthetic to make it numb. A small mouthguard will be put between your teeth to protect them. A highly qualified anaesthetist and nursing staff will monitor your vital signs during the procedure and will attempt to make you as comfortable as possible.
The procedure takes about 30 minutes. Once sedated and lying in a comfortable position on your left side, the doctor inserts the colonoscope through the anus and slowly guides it into the colon. A small camera at 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 Once the scope has reached the other end of the large bowel, it is slowly withdrawn and the lining of the bowel is carefully examined again.
Following the procedure you will remain in the recovery area for an hour or two until the sedation medication wears off. You will usually be given something light to eat and drink once you are awake.
Your doctor will briefly inform you of your test results on the day of the procedure. A follow-up appointment may be made to discuss the test results more fully. The results of any biopsies or samples taken will take a few days.
Because of the sedation given during the procedure, it is very important that you do not drive a car, travel on public transport alone, operate machinery, sign legal documents or drink alcohol on the same day after the test. It is strongly advised that a friend or relative take you home and stay with you for 24 hrs.
Although complications can occur, they are rare when the procedure is performed by doctors who are specially trained in colonoscopy. In Australia, very few people experience serious side-effects from colonoscopy and polypectomy (polyp removal). The chance of complications depends on the exact type of procedure that is being performed and other factors including your general health.
NB: Depending on the reason for the procedure, there may be risks of NOT having the procedure e.g. missed disease or delayed diagnosis. These risks may be fatal, e.g. delayed diagnosis of cancer.
Common risks of the procedure include:
Mild abdominal pain, bloating and discomfort
Nausea and vomiting.
Faintness or dizziness, especially when you start to move around.
Headache.
Pain, redness or bruising at the sedation injection site
Allergy to medications given at time of the procedure.
Minor rectal bleeding
Very rarely (one in 1,000 cases), the bowel lining may be torn or splenic injury may happen, and if this occurs you will be admitted to hospital and surgery may be required to repair it.
Colonoscopy is considered to provide the most accurate assessment of the colon. However, no test is perfect and there is a risk that an abnormality may not be detected. A colonoscopy can miss lesions in the bowel in 2% – 8% of cases. For serious lesions such as cancer, the chance is much less, but still present.
If you have severe abdominal pain, persistent bleeding from anus, fever or any other symptoms that may concern you, you should contact the hospital or your doctor’s rooms immediately.