Overview

What is colon cancer?

Colon cancer happens when cells that are not normal grow in your colon. These cells often form in polyps, which are small growths in the colon. Not all colon polyps turn into cancer. But most colon cancer starts in a polyp.

Colon cancer occurs most often in people older than 50.

Who should be screened for it?

Your risk for colorectal cancer gets higher as you get older. If you are not at high risk, experts recommend regular screening for adults ages 50 to 74. Talk with your doctor about your risk and when to start and stop screening.

How often you need screening depends on the type of test you get:

Stool tests.

Every year for FIT.

Tests that look inside the colon.

Every 10 years for sigmoidoscopy.

Every 10 years for colonoscopy (Figure 1).

Experts agree that people at higher risk may need to be tested sooner and more often. This includes people who have a strong family history of colon cancer. Talk to your doctor about which test is best for you and when to be tested.

Colon Cancer: Screening Tests and What the Results Mean, video

Colon polyps: Fast facts, video

Figure 1 - Colonoscopy

Anatomy of the colon

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During a colonoscopy, the doctor will be able to look at the inside of your entire large intestine (your colon). This includes the cecum (which is attached to the small intestine and is the beginning of the large intestine), the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.

The colonoscope is placed in the colon

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You will be given medicine through a needle in your vein. This is called an intravenous (IV) line. The medicine will make you sleepy. You may lie on your left side with your knees pulled up to your belly. The doctor will gently put a gloved finger into your anus. Then he or she will put the thin, flexible colonoscope in your anus and move it slowly through your colon.

The doctor looks inside the colon: Part 1

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The doctor can look at the inside lining of your colon through the scope or on a computer screen hooked up to the scope.

The doctor looks inside the colon: Part 2

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The doctor will look at the whole length of your colon as the scope is gently moved in and then out of your colon.

Views of a normal colon and a colon polyp

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A polyp is a small growth of excess tissue that often grows on a stem or stalk. Colon polyps are growths in the colon or rectum.

Some polyps are attached to the wall of the colon or rectum by a stalk or stem (pedunculated). Some have a broad base with little or no stalk (sessile).

Current as of: October 25, 2023

Author: Ignite Healthwise, LLC Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.