What is the purpose of a colonoscopy?

This examination is intended to explore the large intestine (colon) using a flexible endoscope inserted through the anus. It is used to look for abnormalities in the colon and, if necessary, to collect samples for analysis under a microscope. Polyps are sometimes found during this examination. Whenever possible, they are removed or destroyed to prevent them from developing into a tumor.


A colonoscopy takes 15 to 30 minutes. The preparation for the examination lasts several hours and a period of recovery and monitoring is required after the examination. A whole day should therefore be planned. The return home is authorized on the same day. However, in some cases, such as particular difficulties during the examination, removal of a large polyp, etc., a short hospitalization for monitoring purposes may be necessary.

How to prepare for it?

The large intestine must be perfectly clean for the examination to be conducted in good conditions. You must therefore follow the instructions given to you for the preparation, which consists in drinking a solution that aims to empty the colon. Concretely, the intestinal preparation is done by the patient at home and most often includes a diet without fibers started a few days before the examination. The evening before the colonoscopy, the patient takes a large volume of the oral solution with the objective of "flushing" the colon. This preparation is often carried out in two steps and completed in the morning of the day of the examination. Of note, the quality of the examination, i.e. a good inspection of the colonic mucosa and the possible removal of polyps, depends greatly on the quality of the bowel preparation. Indeed, a poor preparation of the intestine with persistent stool in the colon will not allow the gastroenterologist to perform optimal polyp screening. Physician and patient each have a key role to play in a quality examination!

Always inform the physician of your allergies and medications, especially those that affect blood coagulation, such as Aspirin® and Sintrom®.


Colonoscopy is often performed in a day hospital under light sedation in the presence of an anesthesiologist to ensure better patient comfort. The examination lasts about 15 minutes on average. The endoscope is inserted through the anus and progressively guided along the entire length of the colon in order to examine it fully. Once it reaches the point where the small intestine ends in the colon, the last few centimeters can sometimes be examined. This is called an "ileoscopy". The examination of this area is important in certain diseases affecting the end of the small intestine. If one or more polyps are detected, they are generally removed using a forceps or an electric scalpel, which is called a “polypectomy”. Small tissue samples (biopsies) of the colon mucosa are also often collected and examined under a microscope.

Between each examination and according to current recommendations, the equipment is disinfected and the accessories are sterilized or discarded (single-use material) to prevent any infection transmission.

What happens after the procedure ?

After a period of time spent in the recovery room, the patient will see his or her gastroenterologist again, who will give the results of the examination as well as recommendations for further follow-up. If polyps have been removed during the examination, a follow-up colonoscopy will often be indicated within a time frame determined by the physician. The results of the microscopic analysis of the resected polyps are sent to the patient's attending physician approximately 8 to 10 days later.

Risks and discomforts

The passage of the curves of the large intestine can make the examination uncomfortable and require the administration of a sedative. In some cases, the examination is performed under anesthesia (called "sedation"). Abdominal cramps are frequent after the examination. They are relieved by the emission of gas (air insufflated during the examination).


Colonoscopy has few risks. Maximum precautions are taken to minimize inconvenience and risk. There is a low risk (< 1%) of perforation or hemorrhage, especially when a polyp is removed. Other exceptional complications are possible such as cardiorespiratory problems. In case of complications, hospitalization may be proposed and surgical treatment may be necessary.

Complications usually occur during the endoscopy but can also appear a few days after the examination (abdominal pain, loss of blood in the stool, fever, etc.). It is then very important to contact the doctor or anesthesiologist who took care of you immediately on +32 2764 28 23 or +32 2 764 28 39. If you are unable to contact them, please inform your doctor or go to the emergency room.

Contraindications / Alternative

If the examination suggested by your doctor is not performed, this may have harmful consequences because a disease currently curable by medication, endoscopic treatment, or surgery may not be discovered.

The return home

Driving a vehicle on the day of an exam is not recommended because of the painkillers received. The return home must be ensured by a third party, by public transport or by cab. For the same reasons, making important decisions that require your complete lucidity on the day of the exam is not advisable.

Additional information

Colonoscopy is the best method to examine the colon. Other examinations are possible (e.g., X-ray of the colon by barium enema). They do not allow to take samples and/or to remove polyps.

The doctor is at your disposal for any further information.


Hepato-gastroenterology consultation secretariat

+32 2 764 28 23
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