colonoscopy
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. A colonoscopy can help your doctor explore possible causes of abdominal pain, rectal bleeding, chronic diarrhea and other intestinal problems.
- Screen for colon cancer. If you're age 45 or older and at average risk of colon cancer — you have no colon cancer risk factors other than age — your doctor may recommend a colonoscopy every 10 years. If you have other risk factors, your doctor may recommend a screen sooner. Colonoscopy is one of a few options for colon cancer screening. Talk with your doctor about the best options for you.
- Look for more polyps. If you have had polyps before, your doctor may recommend a follow-up colonoscopy to look for and remove any additional polyps. This is done to reduce your risk of colon cancer.
- Treat an issue. Sometimes, a colonoscopy may be done for treatment purposes, such as placing a stent or removing an object in your colon.
What you can expect
During the procedure
During a colonoscopy, you'll wear a gown, but likely nothing else. Sedation or anesthesia is usually recommended. In most cases, the sedative is combined with pain medication given directly into your blood stream (intravenously) to lessen any discomfort.
You'll begin the exam lying on your side on the exam table, The doctor will insert a colonoscope into your rectum.
The scope — which is long enough to reach the entire length of your colon — contains a light and a tube (channel) that allows the doctor to pump air, carbon dioxide or water into your colon. The air or carbon dioxide inflates the colon, which provides a better view of the lining of the colon.
The colonoscope also contains a tiny video camera at its tip. The camera sends images to an external monitor so that the doctor can study the inside of your colon.
The doctor can also insert instruments through the channel to take tissue samples (biopsies) or remove polyps or other areas of abnormal tissue.
A colonoscopy typically takes about 30 to 60 minutes.
After the procedure
After the exam, it takes about an hour to begin to recover from the sedative. You'll need someone to take you home because it can take up to a day for the full effects of the sedative to wear off. Don't drive or make important decisions or go back to work for the rest of the day.
You may feel bloated or pass gas for a few hours after the exam, as you clear the air from your colon. Walking may help relieve any discomfort.
You may also notice a small amount of blood with your first bowel movement after the exam. Usually this isn't cause for alarm. Consult your doctor if you continue to pass blood or blood clots or if you have persistent abdominal pain or a fever. While unlikely, this may occur immediately or in the first few days after the procedure, but may be delayed for up to 1 to 2 weeks.
Results
Your doctor will review the results of the colonoscopy and then share the results with you.
Negative result
A colonoscopy is considered negative if the doctor doesn't find any abnormalities in the colon.
Your doctor may recommend that you have another colonoscopy:
- In 10 years, if you're at average risk of colon cancer and you have no colon cancer risk factors other than age or if you have benign small polyps.
- In 1 to 7 years, depending on a variety of factors: The number, size and type of polyps removed; if you have a history of polyps in previous colonoscopy procedures; if you have certain genetic syndromes; or if you have a family history of colon cancer.
If there was residual stool in the colon that prevented complete examination of your colon, your doctor may recommend a repeat colonoscopy. How soon will depend on the amount of stool and how much of your colon was able to be seen. Your doctor may recommend a different bowel preparation to ensure that your bowel is completely emptied before the next colonoscopy.
Positive result
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.
Depending on the size and number of polyps, you may need to follow a more rigorous surveillance schedule in the future to look for more polyps.
If your doctor finds one or two polyps less than 0.4 inch (1 centimeter) in diameter, he or she may recommend a repeat colonoscopy in 7 to 10 years, depending on your other risk factors for colon cancer.
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
If you have a polyp or other abnormal tissue that couldn't be removed during the colonoscopy, your doctor may recommend a repeat exam with a gastroenterologist who has special expertise in removing large polyps, or surgery.