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A colonoscopy is an examination with the colonoscope, which is a flexible
fiberoptic instrument (made of fine glass fibres which transfer the light). The
colonoscope is connected to a screen, a light source and an insufflattion-
suction device.
The colonoscope measures approximately 120 centimetres and the aim of the
examination is to view the whole of the large bowel and, if indicated, even the
last part of the small bowel (terminal ileum).
In order for the examination to take place the large bowel has to be empty of
stools. Bowel preparation takes place the day before the colonoscopy.
Bowel preparation consists of:
a. strong laxatives (Picolax, Fleet etc.)
b. a diet consisting only of fluids for 24 hours.
During the bowel preparation the patient has to go to the toilet very frequently
and needs to stay at home. It is necessary to drink a lot of fluids because
there is risk of dehydration from excessive diarrhoea, particularly if the
examination is on days of hot weather. The experience of bowel preparation can
be a bit of an ordeal for patients who are elderly or very frail. Those patients
may need to be admitted to the hospital to have supplemental intravenous fluids
during bowel preparation.
Bowel preparation is contraindicated in patients with renal failure, cardiac
failure, dementia or those who are simply too frail and therefore “unfit for bowel
preparation”.
All drugs that affect the clotting of blood have to be stopped 4 - 7 days
before the procedure. Those drugs are warfarin, aspirin, clopidogrel and
other anti-platelet factors.
After successful bowel preparation the patient attends the Endoscopy suite
where the informed consent is signed or confirmed if it has been signed
beforehand.
The informed consent includes the risks of the procedure.
Colonoscopy is a safe procedure in most cases, however there are three main
risks:
a. perforation of the colon
b. bleeding
c. drug reactions
The risk of the above complications varies between 1:500 and 1:1000.
Perforation is more common in the presence of diverticula and bleeding
complicates biopsy or polypectomy.If perforation or bleeding occurs an
operation may be required.
An intravenous line is used to administer sedation. This is “conscious sedation”
because the patient needs to maintain an airway and co-operate during the
procedure. There are several different schemes and opinions vary but the more
commonly used medications in the UK are pethidine, midazolam and fentanyl.
Most patients tolerate the procedure very well and some do not even remember
anything at the end (usually due to the amnesic effect of midazolam). However
there are some patients who do not respond well to sedation and find
colonoscopy uncomfortable despite heavy sedation. This is particularly true for
patients with irritable bowel syndrome and the discomfort they experience is
believed to be caused by spasms of the colon during the procedure.
During the colonoscopy suspicious areas or tumours are biopsied or polyps are
removed with the help of several instruments such as forceps, snares, baskets,
diathermy etc.
A great advantage of colonoscopy is that it can also offer treatment of polyps
and other conditions at the same time.
Oxygen is provided throughout the procedure and the oxygen saturation and
pulse is monitored continuously.
The patient takes approximately 1 hour to recover from the sedation. If the
sedation remains too deep antidotes such as anexate can be given.
The patient is not allowed to leave unaccompanied, an escort must be available.
The patient should not spend the night after colonoscopy alone.
There might be some abdominal distension and discomfort after colonoscopy
but this usually resolves quickly. Development of severe constant pain in the
hours after colonoscopy should raise the suspicion of perforation and the
patient should seek help at the hospital.
Colonoscopy