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Comprehending colonoscopy

A colonoscopy is a test where an operator – a doctor – looks into one’s colon. The colon is sometimes called the large intestine or large bowel. The colon is the part of the gut which comes after the small intestine. The last part of the colon leads into the rectum where stools (faeces) are stored before being passed out from the back passage (anus).

A colonoscope is a thin, flexible telescope. It is about as thick as a little finger. It is passed through the anus and into the colon. It can be pushed all the way round the colon as far as the caecum (where the small and large intestine meet).

Another test called sigmoidoscopy looks at the rectum and the lower part of the colon.

The colonoscope contains fibre-optic channels which allow light to shine down so the operator can see inside the colon.

The colonoscope also has a side channel down which devices can pass. These can be manipulated by the operator. For example, the operator may take a small sample (biopsy) from the inside lining of the colon by using a thin ‘grabbing’ instrument which is passed down a side channel.

Who should undergo colonoscopy?

A colonoscopy may be advised if one has symptoms such as:

Persistent diarrhoea

Pains in the lower tummy (abdomen).

Bleeding from the back passage (anus).

Other symptoms thought to be coming from the colon.

The sort of conditions which can be confirmed include:

Pouches which form inside colon (Diverticula)

Ulcerative colitis

Colonic polyps

Colorectal cancer

Crohn’s disease

Various other conditions may also be detected. Also, a colonoscopy is often normal. However, a normal result may help to rule out certain possible causes of one’s symptoms.

The process of colonoscopy

Colonoscopy is usually done as an outpatient or day case. It is a routine test which is commonly done. One is usually given a sedative to help one to relax. This is usually given by an injection into a vein in the back of one’s hand. The sedative can make one drowsy but it does not put the person to sleep. It is not a general anaesthetic.

One is made to lie on one’s side on a couch. The operator will gently push the end of the colonoscope into the back passage (anus) and up into the colon. Colonoscopes transmit pictures through a camera attachment on to a TV monitor for the operator to look at.

Air is passed down a channel in the colonoscope into the colon to make the inside lining easier to see. This may cause one to feel as if one wants to go to the toilet (although there will be no stools (faeces) to pass). The air may also make one feel bloated, cause some mild ‘wind pains’, and may cause one to pass wind. This is normal and there is no need to be embarrassed, as the operator will expect this to happen.

The operator may take small samples (biopsies) of some parts of the inside lining of the colon – depending on why the test is done. This is painless. The biopsy samples are sent to the laboratory for testing and to be looked at under the microscope. Also, it is possible to remove polyps, which may be found, with an instrument attached to a colonoscope. (Polyps are small lumps of tissue which hang from the inside lining of the colon.) At the end of the procedure the colonoscope is gently pulled out.

A colonoscopy usually takes about 20-30 minutes. A colonoscopy does not usually hurt but it can be a little uncomfortable, particularly when the colonoscope is first passed into the anus.

A newer type of colonoscopy called a virtual colonoscopy is available. It is sometimes known as computerised tomography (CT) colonography or CT colonoscopy. It may be suggested as appropriate for you to have if:

You have had a conventional colonoscopy and your doctor was not able to visualise the entire large bowel.

There are technical reasons why it is difficult to do a colonoscopy.

This type of colonoscopy is performed using a CT scan to take an image of the bowel. A thin tube is put into the back passage to put air into the bowel to help produce clear images. The CT scan then produces images of the large bowel.

Getting prepared for colonoscopy

Each hospital will have different protocol so it should be follwed. Usually involves taking laxative to empty large bowel. One might pass stool upto 10 times so its important to keep one hydrated.

Post colonoscopy care

Most people are ready to go home after resting for half an hour or so. One may need to stay a bit longer for observation if one had had any small lumps of tissue (polyps) removed.

If a sedative is administered – one may take a bit longer to be ready to go home. The sedative will normally make you feel quite pleasant and relaxed.

However, one should not drive, operate machinery, drink alcohol, take important decisions or sign documents for 24 hours after having the sedative.

One will need somebody to accompany him home and to stay with him for 24 hours until the effects have fully worn off. Most people are able to resume normal activities after 24 hours.

The result from any sample (biopsy) may take a few days.

Could there any side-effects or challenges from having a colonoscopy?

Most colonoscopies are done without any problem. The sedative may cause tiredness or sleepiness for several hours afterwards. One may pass a small amount of blood from the back passage (anus) if a biopsy was taken or if a small lump of tissue (polyp) was removed. One may also have leakage of liquid accompanied by gas for up to 24 hours after taking the last dose of laxatives.

Occasionally, the colonoscope may cause damage to the colon. This may cause bleeding, infection and (rarely) a hole (perforation). If any of the following occur within 48 hours after a colonoscopy, a doctor should be consulted immediately:

Raised temperature (fever).

Passing a lot of blood from the anus.

Tummy (abdominal) pain. (In particular if it becomes gradually worse and is different or more intense to any ‘usual’ pains that one may have.)


Colonoscopy is a test to assess the colon (large intestine). Though it is an invasive proecedure its very rare to have complications. Medicines will need to be taken so that one’s colon can be visualised. Usually it take around 30mins for procedure. Now a days precancerous lesions can be completely excised. Even early cancers can be completely excised. Regular survillance is needed in these cases.