Endoscopy & Tests

Medical content written by Dr Youssef BENNANI, hepato-gastroenterologist · Updated on

Colonoscopy

Colonoscopy

Colonoscopy is the reference examination for detecting abnormalities of the colon. It allows samples (biopsies) to be taken and polyps to be removed when they are found during the examination.

Why have a colonoscopy?

Colonoscopy is the reference examination for detecting abnormalities of the colon. It allows samples (biopsies) to be taken and polyps to be removed if they are found during the examination. No other examination can currently replace colonoscopy.

In some cases, the examination may be incomplete: a CT colonography is then recommended to study the entire colon. If the bowel preparation is not perfect, small lesions may sometimes be missed even when the examination is complete. Removing polyps does not prevent them from coming back, so further colonoscopies may be needed.

The colon must be perfectly clean for optimal visibility.

  • A low-fiber diet is recommended for 2 to 3 days before the examination
  • Your doctor will prescribe a bowel-cleansing solution to drink the day before and the morning of the examination; follow the instructions carefully
  • Do not eat anything for 6 hours before the examination; smoking is not allowed

In some cases, even when the instructions are followed, the preparation may be insufficient and the examination may have to be stopped. A new colonoscopy will then be scheduled with a 2-day bowel preparation.

See our detailed guide: Colonoscopy preparation.

The examination is done as an outpatient procedure, usually under general anesthesia. A flexible instrument is inserted through the anus; air is blown in to unfold the wall and advance along the entire colon. Biopsies are taken if needed. The examination lasts 15 to 30 minutes, sometimes longer depending on technical difficulties.

Polyps are mushroom-shaped growths on the wall of the colon. Some can turn into cancer. When their size allows, they can be removed during the colonoscopy; otherwise, a later removal will be scheduled. They are removed with an electric scalpel that cuts and coagulates; in some cases, they need to be lifted by injecting fluid at their base.

Apart from complications related to anesthesia, complications of colonoscopy are very rare and may occur even when the examination is performed with competence and safety in line with current scientific standards:

  • Perforation of the colon may require surgery
  • Bleeding may, in exceptional cases, require surgical treatment

Under validated cleaning, disinfection and sterilization conditions, no case of viral infection transmission (hepatitis B, hepatitis C, HIV/AIDS…) has ever been detected.

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