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Colonoscopy

Medically Reviewed by Sabrina Felson, MD on November 02, 2021

Colonoscopy (koh-luh-NAH-skuh-pee) lets the physician look inside your entire large intestine, from the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. The procedure is used as a tool for routine colon cancer screening and prevention in people beginning at age 45. Small growths called polyps can be removed during the colonoscopy before they have the chance to grow into a colorectal cancer.

Colonoscopy is also used to diagnose the causes of unexplained blood in the stool or changes in bowel habits. Colonoscopy enables the doctor to see inflamed tissue, abnormal growths, ulcers, bleeding, and muscle spasms in the colon.

For the procedure, you will lie on your left side on the examining table. You will be given pain medication and a mild sedative to keep you comfortable and to help you relax during the exam. The physician will insert a long, flexible, lighted tube into your rectum and slowly guide it into your colon. The tube is called a colonoscope (koh-LON-oh-skope). The scope transmits an image of the inside of the colon onto a television or computer monitor, so the physician can carefully examine the lining of the colon. The scope bends, so the physician can move it around the curves of your colon. The scope also blows air into your colon, which inflates the colon and helps the physician see better.

If anything unusual is in your colon, like a polyp or inflamed tissue, the physician can remove it or a piece of it using tiny instruments passed through the scope. That tissue (biopsy) is then sent to a lab for testing. If there is bleeding in the colon, the physician can use the scope to pass a laser, heater probe or electrical probe, or inject special medicines, to stop the bleeding.

Bleeding and puncture of the colon are possible complications of colonoscopy. However, such complications are uncommon.

Colonoscopy takes 30 to 60 minutes. The sedative and pain medicine should keep you from feeling much discomfort during the exam. You will need to remain at the physician's office for 1 to 2 hours until the sedative wears off.

Preparation for a Colonoscopy

Your colon must be completely empty for the colonoscopy to be thorough and complete. To prepare for the procedure, you may have to follow a liquid diet for 1 to 3 days beforehand. A liquid diet means fat-free bouillon or broth, gelatin, strained fruit juice, water, plain coffee, plain tea, or diet soda. You will need a bowel prep, which usually requires drinking a fluid that will cause bowel-clearing diarrhea. Also, you must arrange for someone to take you home afterward; you will not be allowed to drive because of the sedatives. Your doctor may give you other special instructions.

Show Sources

SOURCES:
The National Digestive Diseases Information Clearinghouse of The National Institutes of Health. "Colonoscopy." NIH Publication No. 98-4331. July 7, 1998.

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