Colonoscopy: what is it and how to prepare for it?

Published 28 Jan 2022 • By Claudia Lima

Colonoscopy is a medical examination performed under general or local anaesthesia. It allows to detect intestinal disorders and is prescribed for those who experience digestive symptoms, but is also part of the bowel cancer prevention strategies.
Before getting a colonoscopy, the patient needs to prepare for it. In what way?

Read our article to find it all out!

 Colonoscopy: what is it and how to prepare for it?

What is a colonoscopy? 

Colonoscopy is a medical procedure performed by a gastroenterologist assisted by an anaesthetist. It is a standard examination which allows to visualise the interior of the large intestine and the final section of the small intestine.

The device used in the procedure is called a colonoscope, a medical instrument that has a flexible tube fitted with a small camera, a lamp and, if necessary, surgical instruments. This device is introduced into the body via the anus under local or general anaesthetic.

This examination is the most accurate test for bowel cancer, as well as for chronic inflammatory diseases of the colon, such as Crohn's disease and ulcerative colitis. If the disease is detected early, the chances of recovery increase significantly. For example, polyps can be detected and treated before they develop into cancer.

Why get a colonoscopy? 

Your doctor may prescribe a colonoscopy in case of unexplained digestive symptoms, such as abdominal cramps and pain, or the presence of black blood in the stool. It is also prescribed if the patient has a family history of bowel cancer, digestive bleeding and chronic diarrhoea.

Finally, colonoscopy becomes necessary if during the first stage of bowel cancer screening blood is found in the patient's stool.

Bowel cancer screening is an important part of cancer prevention programmes in many countries. About 95% of bowel cancers are diagnosed after the age of 50, both in men and in women. In the UK, screening is recommended for people aged 60 and older, to be done every 2 years.

How to prepare for a colonoscopy? 

As colonoscopy requires a general or local anaesthetic, the patient must see an anaesthetist 8 to 10 days before the procedure.

In order to carry out this examination, the colon must be cleansed, generally by ingesting a preparation that will allow all the matter present in the intestines to be evacuated.

The evacuation of the faeces is essential for the success of the procedure: thus the doctor will be able to correctly visualise the walls of the intestines, as well as the lesions, if there are any. In order to cleanse the colon, the patient needs to take laxative medicines, some of which are available in the form of tablets (Phospho-soda®, Moviprep®, Izinova®).

Prior to the procedure, the patient receives recommendations regarding the diet to be followed for several days before the procedure, and the bowel lavage.

Here are some of the recommendations:

  • Follow a low-residue diet 5 days before the examination: no fruit and vegetables containing seeds (tomatoes, cucumbers, grapes), no foods containing seeds (wholemeal bread, jam); a list of allowed and forbidden foods can be given to the patient,
  • Eat light meals the day before, drink only coffee, tea and plain water, no juice with pulp,
  • Take the laxative preparation for colon cleansing, the hour of intake and the dose depend on the time when your examination is scheduled; do not consume anything else, neither meals nor medicines until the end of the examination. You should not smoke either, because of the increase in gastric secretions due to smoking.

How is a colonoscopy performed? 

The examination is performed as an outpatient surgery, i.e. in a hospital or clinic, during a hospital stay of less than 12 hours without overnight accommodation.

Depending on the prescription and the general condition of the patient, the colonoscopy is performed under local or general anaesthesia. Once the patient is in the operating theatre, the anaesthetic is administered. Then the colonoscope is introduced into the anus and guided up through the bowel. The gastroenterologist observes the intestines through the camera and at the end of the examination the colonoscope is gently withdrawn and the insufflated air is sucked out.

The examination lasts about twenty minutes and there is little pain upon waking. The patient is monitored in the recovery room, their blood pressure, breathing and general condition is constantly checked.

It is possible to eat and drink normally after a colonoscopy, but it is recommended not to drink alcohol on the day of the procedure.

The results of the examination are usually received immediately after the procedure in the form of a report, which is also sent to the prescribing physician. If a biopsy was performed during the procedure, the results will be available in several days.

It is possible to experience abdominal bloating without pain after the colonoscopy. This is due to the presence of gas in the digestive tract, which passes with the emission of this gas through the anus. Due to the effects of the anaesthesia, it is compulsory to be accompanied by a close relative when leaving the hospital/clinic, and driving a car is forbidden on the day of the procedure. Starting from the next day, you can resume your normal activities.  

Can there be any complications from colonoscopy? 

Complications are rare but they do exist. The main ones are perforation and bleeding.

Apart from the risks associated with any anaesthesia, the risk of complications is in the order of 1 to 4.5 per 1,000 colonoscopies performed, with a greater risk for patients aged 70 and older.

Each patient is informed of the risks before the procedure.

To sum up, colonoscopy allows early detection of diseases, it is an examination performed under anaesthesia so the patient does not feel the pain; it is a short procedure, which presents few risks, but requires special preparation to be successful. The quality of the procedure depends on the quality of the preparation.

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avatar Claudia Lima

Author: Claudia Lima, Health Writer

Claudia is a content creator at Carenity, specializing in health writing.

Claudia holds a master's degree in Entrepreneurship and an Executive MBA in Sales and Marketing Management. She is specialized in... >> Learn more


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