What a colonoscopy is

A colonoscopy lets a doctor look at the inside of your colon (large intestine) and rectum. You are usually asleep or very relaxed. The doctor uses a long, thin, flexible tube with a small camera on the end.

If the doctor finds a polyp, a small growth on the lining, it can usually be removed during the same procedure.

Why it matters

Colorectal cancer is the second leading cause of cancer death in the US. Most colorectal cancers start as polyps that grow slowly over years. Finding and removing polyps can stop cancer before it starts. When cancer is found early, before it spreads, about 9 in 10 people are alive five years later.

Who should be screened, and when

• Ages 45 to 75: most adults at average risk should be screened.
• Ages 76 to 85: decide with your doctor, based on your health and past screening.
• Earlier or more often if a parent, brother, sister or child had colorectal cancer or advanced polyps; if you have had polyps or colorectal cancer before; if you have Crohn's disease or ulcerative colitis; or if an inherited condition runs in your family.

Symptoms are different from screening. If you have blood in your stool, a lasting change in your bowel habits, or belly pain that doesn't go away, see your doctor. Don't wait for a screening date.

Colonoscopy is one of several tests

Stool tests you do at home are another option. Compare the screening tests →