A colonoscopy is a diagnostic screening exam that a physician, usually a gastroenterologist, uses to look inside your large intestine for colon polyps or possible signs of colorectal cancer. How often you should be screened depends on the specific test, your age and your risk for colon cancer.
At what age and how often to have a colonoscopy
If you’re at average risk of colon cancer, we at Westchester Health, recommend that you have a colonoscopy every 10 years, starting at age 50. The procedure may be performed earlier and more often in people at increased risk, including those with a personal or family history of:
- polyps (abnormal growths)
- colorectal cancer
- inflammatory bowel disease
- a hereditary syndrome such as familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer (Lynch syndrome)
Colorectal cancer screening generally starts at age 50 because colon cancer risk increases with age, and more than 90% of cases occur in people aged 50 and over.
Most colorectal cancers start as polyps. The progression from precancerous polyp to cancer is believed to take 10 years or more, although experts don’t really know because clinicians remove polyps when they find them, before they become cancerous. Screening also identifies colon cancer early, when it’s most treatable.
Some guidelines recommend that routine screening continue until age 76, with screening then being an option between ages 76 and 85, depending on overall health and risk factors. Screening is not recommended after age 85.
If you choose colonoscopy, seek out a gastroenterologist with plenty of experience performing the procedure and a facility equipped to handle potential problems.
Why get tested? It’s the best way to prevent colon cancer.
The American Cancer Society believes that preventing colorectal cancer (not just detecting it early) should be a major reason for every individual to get tested. There are a variety of tests currently available. Those that have the best chance of finding both polyps and colon cancer are preferred, if these tests are available to you and you are willing to have them.
Starting at age 50, men and women at average risk for developing colorectal cancer should get one of the screening tests below:
Tests that find polyps and cancer
- Flexible sigmoidoscopy every 5 years*
- Colonoscopy every 10 years
- Double-contrast barium enema every 5 years*
- CT colonography (virtual colonoscopy) every 5 years*
Tests that mainly find cancer
- Guaiac-based fecal occult blood test (gFOBT) every year**
- Fecal immunochemical test (FIT) every year**
- Stool DNA test every 3 years*
*Colonoscopy should be done if test results are positive.
**Highly sensitive versions of these tests should be used with the take-home multiple sample method. A gFOBT or FIT done during a digital rectal exam in the doctor’s office is not enough for screening.
Is a rectal exam enough to screen for colorectal cancer?
In a digital rectal examination, a healthcare provider examines your rectum with a lubricated, gloved finger. Although a DRE is often included as part of a routine physical exam, it’s not recommended as a stand-alone test for colorectal cancer. This simple test, which is not usually painful, can find masses in the anal canal or lower rectum. However, by itself it’s not a good test for detecting colorectal cancer because it only checks the lower rectum.
Doctors often find a small amount of stool in the rectum when doing a DRE. But testing this stool for blood with a gFOBT or FIT is not an acceptable way to screen for colorectal cancer. Research has shown that this type of stool exam will miss more than 90% of colon abnormalities, including most cancers.
People at increased or high risk
If you are at an increased or high risk of colorectal cancer, you might need to start colorectal cancer screening before age 50 and/or be screened more often. The following conditions make your risk higher than average:
- A personal history of colorectal cancer or adenomatous polyps
- A personal history of inflammatory bowel disease (ulcerative colitis or Crohn’s disease)
- A strong family history of colorectal cancer or polyps (see Colorectal cancer risk factors)
- A known family history of a hereditary colorectal cancer syndrome such as familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC)
How to prepare for a colonoscopy
For your colonoscopy to be diagnostically successful, your colon must be empty and “clean.” This means you need to restrict your diet at least 24 hours before the procedure. Clear liquids rather than solids are recommended, such as:
- Sports drinks
Then you need to empty your bowel the night before and the morning of the procedure, typically by taking a series of enemas or drinking a solution of magnesium citrate that causes you to go to the bathroom.
You’ll need someone take you home after the colonoscopy. You will be sedated during the procedure, therefore it won’t be safe for you to drive or operate machinery for at least 8 hours afterward.
How is a colonoscopy performed?
During your colonoscopy, sedatives will be administered through an IV in your arm, putting you to sleep. Then your physician will put a tube-like instrument called a colonoscope into your rectum, with a light and video camera on the tip so he/she can see the lining of your colon and detect if there is a problem. The colonoscope also includes a tube that lets your physician pump in air and inflate your colon, giving him/her a better view of your colon and its lining.
During the exam, your physician can use the tool to take tiny samples of your colon for testing (biopsy). He can also use the tool to remove polyps.
Is it time for you to have a colonoscopy? Please come see us.
If you are age 50 or over and have never had a colonoscopy, please make an appointment with Westchester Health to see one of our gastroenterologists. If you have had the procedure but it’s time to have another one, please make an appointment, too. The sooner we can detect potential problems, the sooner they can be treated before they become more serious.