Colonoscopy
What is a colonoscopy?
A colonoscopy is a frequently performed test to investigate the large bowel. This is an endoscopic test that allows the doctor to look directly at the lining of the bowel. The procedure is used to help doctors diagnose unexplained changes in bowel habits (for example constipation or diarrhoea), abdominal pain, bleeding and weight loss. Colonoscopy can detect inflammatory bowel disease, polyps and cancers. Biopsies can also be taken during the procedure and polyps can be removed.
What preparation is required?
Patients will receive written instructions about the test beforehand. Patients will be given some strong laxatives to clear out the bowel. These laxatives require mixing with water. Patients will be given clear instructions about how to mix them and when to take them. This will vary depending on the time of day that the procedure is scheduled. It is important that patients follow the instructions about what to eat beforehand and when to stop eating. Patients should drink as much clear fluid as possible. Having a clean bowel will allow the doctor to be able to see the lining more accurately. Patients who are having sedation for the procedure, will instructed when to stop drinking beforehand, again it is important that these instructions are strictly adhered to. Patients should inform their doctor if they are diabetic or taking any medication that might thin the blood (including aspirin) as blood thinners may need to be stopped before the procedure. Patients will be asked to sign a consent form after discussing the procedure, its risks, and the benefits with the doctor.
What does the procedure involve?
At the start of the procedure a small needle or canula is passed into a vein in the back of the hand to allow the administration of any sedation required. Patients who choose not to have sedation may use Entonox, also known as gas and air, to control any discomfort. The instrument used during this investigation is called a colonoscope. This is a long flexible tube with a light at the end. It is passed through the anus. This allows the doctor to see images of the inside of the bowel on a screen. In most cases the doctor can see the whole of the colon and sometimes the last part of the small intestine (terminal ileum) as well. If patients are awake for the procedure they can watch as well. The doctor may ask patients to move periodically so the scope can be adjusted for better viewing. During a colonoscopy the doctor can take photographs, take samples of tissue called biopsies from normal and abnormal-looking tissues, as well as remove growths, called polyps, using special tools passed through the scope. Patients may feel mild discomfort or wind pains as the colonoscope is passed round the bowel.
What are the potential risks and complications?
Colonoscopy is a very commonly performed procedure and complications are rare. Colonoscopy carries a very small risk of perforation (tear) of the bowel. Sometimes this might require surgery to repair. If biopsies are taken or if polyps are removed bleeding may occur from the site. This is usually minor and may stop on its own or require treatment using a heat probe or injection through the colonoscope. Side effects from sedatives (if given) are rare. These can include problems with your breathing, blood pressure and heart rate. These are usually shortlived and quickly treated. Sometimes it may not be possible to complete the procedure successfully and it may need to be done again, alternatively a different type of test may be suggested to look at the bowel.
After the procedure
A colonoscopy takes about 30 minutes to complete. The doctor will be able to tell the patient the result straight after the procedure. Any tissue samples taken will take a few days to be processed by a pathologist. The doctor will normally share the results of any biopsies at a follow-up consultation. Patients may feel bloated and have some wind-like pains afterwards. These usually settle very quickly. If patients have had sedation for the procedure, they will need to recover fully before going home. Patients should not drive, climb ladders, or sign important documents for 24 hours after the procedure. If patients develop severe pain or persistent bleeding after they have gone home they should contact the hospital, their GP or their local A&E department immediately, for further advice.
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