Overview
A colonoscopy is an exam used to look for changes — such as swollen, irritated tissues, polyps or cancer — in the large intestine (colon) and rectum.
During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon.
If necessary, polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy. Tissue samples (biopsies) can be taken during a colonoscopy as well.
Why it's done
Your doctor may recommend a colonoscopy to:
- Investigate intestinal signs and symptoms
- Screen for colon cancer
- Look for more polyps
- Treat an issue
Risks
A colonoscopy poses few risks. Rarely, complications of a colonoscopy may include:
- A reaction to the sedative used during the exam
- Bleeding from the site where a tissue sample (biopsy) was taken or a polyp or other abnormal tissue was removed
- A tear in the colon or rectum wall (perforation)
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Results
A colonoscopy is considered positive if the doctor finds any polyps or abnormal tissue in the colon. Most polyps aren't cancerous, but some can be precancerous. Polyps removed during colonoscopy are sent to a laboratory for analysis to determine whether they are cancerous, precancerous or noncancerous.
Your doctor will recommend another colonoscopy sooner if you have:
- More than two polyps
- A large polyp — larger than 0.4 inch (1 centimeter)
- Polyps and also residual stool in the colon that prevents complete examination of the colon
- Polyps with certain cell characteristics that indicate a higher risk of future cancer
- Cancerous polyps
