Indications for colonoscopy
There are a number of diagnostic reasons for performing a colonoscopy:
• This is a useful investigation in patients presenting with abnormal lower GI tract bleeding, changes in bowel habit, abdominal pain and to further investigate abnormalities detected on other examinations such as barium enemas.
• As colonoscopies can directly visualise the bowel wall and can also sample tissue, they can help investigate inflammation and ulceration of the bowel (eg. inflammatory bowel disease), diverticulae and abnormal growths (polyps/tumours).
Colonoscopy is also a therapeutic procedure. Lumps from the bowel can be removed by the use of diathermy snares (heated loops of wire). This is sometimes called a polypectomy. Abnormal vessels (angiodysplasia) can be 'cauterised' (again, by the use of diathermy) and volvulus (twisted bowel loops) can be un-twisted.
How is it performed?
In a clinical scenario, always remember to do the basics first: introduce yourself, check the patient's identity and explain what you are going to talk to them about.
Preparation:
The bowel needs to be empty in order to obtain a clear picture, so patients are given a laxative on the day of the procedure. Patients are also encouraged to drink clear fluids the day before the test for the same reasons. On the day, they are requested not to eat or drink for 6 hours prior to the procedure.
The procedure:
Colonoscopy is performed as an outpatient procedure, and takes around 20-40 minutes. Patients have to lie on their left side during the examination. A sedative is usually given via a cannula - this is usually a benzodiazepine, such as Midazolam. This will make the patient feel drowsy, but will help them relax throughout the investigation. It also causes amnesia, so the patient will not remember much of the procedure afterwards. The colonoscope is lubricated with some jelly, and is then gently inserted into the bowel through the back passage. Air is often blown into the bowel to improve the view of the bowel lining. This can can sometimes cause wind and a feeling of bloatedness or 'wanting to go to the toilet' afterwards, but this does resolve soon after.
After the test: The patient will be taken to the recovery room and left to rest for around 30 minutes (until the bulk of the sedation wears off). They may sometimes be asked to remain for observation (particularly if they are frail or if a large number of biopsies have been performed). Due to the sedation, they must not drink alcohol, drive or operate machinery until the next day. Patients will therefore need someone to collect them from the hospital.
After your explanation, always ask the patient if they have any further questions or concerns. Don't forget to discuss the complications.
Complications
As with most 'invasive' procedures, patients in the UK will be required to sign a standardised consent form prior to the procedure. In order to do this, the patient must be competent, the consent must be based upon comprehensive information, and must be free from coercion (should not be forced). Bear in mind though, that despite this (and rather bizarrely), a consent form is not a legally valid document! In any case, you should discuss the following risks with patients prior to a colonoscopy:
Colonoscopies involve a small risk of complications. The main two, are perforation and bleeding. The overall mortality rate is quoted as 0.02%.
