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January 20, 2017

What is a colonoscopy?

Colonoscopy is a procedure that lets your healthcare provider check the inside of your entire large intestine or colon.

The procedure is done using a long, flexible tube (a colonoscope). The tube has a light and tiny camera on one end. It is put in your rectum and moved into your colon.

In addition to letting your provider see the inside of your colon, the tube can be used to:

Clean the lining of your colon with a water jet (irrigate)

Remove any liquid stool with a suction device

Inject air in your bowel to make it easier to see inside

Work inside your bowel with surgical tools

During a colonoscopy, your provider may remove tissue or abnormal growths (polyps) for further examination. He or she may also be able to treat problems that are found.

The large intestine or colon is the last section of your digestive system. It absorbs water to change waste from liquid to solid stool. The large intestine is about 5 feet long in adults. It has 4 sections:

Ascending colon. This extends upward on the right side of your belly.

Transverse colon. This extends from the ascending colon across your body to the left side.

Descending colon. This extends from the transverse colon downward on your left side.

Sigmoid colon. This is named because of its S-shape. It extends from the descending colon to your rectum.

The rectum joins the anus. This is the opening where stool passes out of your body.

Why might I need a colonoscopy?

Colonoscopy can help your provider look for problems in your colon. These include any early signs of cancer, red or swollen (inflamed) tissue, open sores (ulcers), and bleeding.

Colonoscopy is also used to screen for colorectal cancer. Screening means looking for cancer in people who don’t have any symptoms of the disease.

A colonoscopy may be used to check and if needed treat things such as:

Colon polyps



Redness or swelling (inflammation)

Pouches (diverticula) along the colon wall

Narrowed areas (strictures) of the colon

Any objects that might be in the colon

It may also be used to find the cause of unexplained, long-term (chronic) diarrhea or bleeding in the GI (gastrointestinal) tract. It can also be used to check the colon after cancer treatment.

Colonoscopy may be used when other tests (such as a barium enema, CT colography, tests for blood in stool, stool DNA tests, or sigmoidoscopy) show the need for more testing.

Your healthcare provider may have other reasons to recommend a colonoscopy.