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Frequently Asked Questions About Colorectal Cancer Screening

The following frequently asked questions will help explain what colorectal cancer is, and the various screening tests available.


Colorectal Cancer

Types of Colorectal Cancer Screenings

Getting Ready for a Colorectal Cancer Screening

Colorectal Cancer


What is colorectal cancer?

Cancer is a group of diseases in which there is abnormal and uncontrolled growth of cells in the body.  If left untreated, cancer cells can spread to other parts of the body.


"Colorectal" refers to the colon and rectum. They make up the large intestine. This type of cancer can begin anywhere in the large intestine. Most of these cancers begin as pre-cancerous abnormal growths (polyps) inside the colon or rectum. 

Should I be screened for colorectal cancer?

The exact causes of colorectal cancer are not known. However, studies have shown that certain factors are linked to an increased chance of developing this disease. The following groups of people are at high-risk and should be screened for colorectal cancer:

  • Family history of colorectal cancer: Close relatives (parents, siblings, or children) of a person who has had colorectal cancer are more likely to develop this type of cancer, especially if the family member developed the cancer at a young age. If many family members have had colorectal cancer, the chances increase even more.
  • Personal history of colorectal cancer: A person who has already had colorectal cancer is at an increased risk of developing colorectal cancer a second time.
  • Ulcerative colitis or Crohn colitis: People who have ulcerative colitis or Crohn colitis may be more likely to develop colorectal cancer than people who do not have these conditions.
  • Familial adenomatous polyposis (FAP): FAP is a rare, inherited condition. Because individuals with this condition are extremely likely to develop colorectal cancer, they are often treated with surgery to remove the colon and rectum in an operation called a colectomy.

Talk with your practitioner if you have any of the above factors that put you at high-risk for developing colorectal cancer. You may need to be screened before the recommended 50 years of age.

Why should I have a colonoscopy?

Colonoscopy is used to prevent colorectal cancer from developing. The test can find inflamed tissue, ulcers, and polyps which may lead to colorectal cancer. Screening tests find cancer early, when treatment works best and the chance to recover fully is very high. It can help doctors diagnose unexplained changes in bowel habits, abdominal pain, bleeding from the rectum, and weight loss.

Is there anything I can do to reduce my risk for this cancer?

There is strong data that supports the idea that having regular screening tests for colorectal cancer starting at age 50 reduces deaths. Screening tests can find polyps before they become cancer in the colon and rectum. The polyps can be removed at that time before they can grow and develop into a colorectal cancer.


Studies have also shown that increased physical activity and keeping a healthy weight can decrease the risk for colorectal cancer. Studies are less clear about other ways to prevent colorectal cancer.


Mainly, the best way to reduce your risk of colorectal cancer is by having regular colorectal cancer screening tests starting at age 50.

What are the symptoms?

People who have polyps or this type of cancer don't usually have symptoms, especially at first. Someone could have polyps or cancer and not know it. If there are symptoms, they may include

  • Blood in or on your stool (bowel movement)
  • Pains, aches, or cramps in your stomach that don't go away
  • Losing weight and you don't know why
  • Change in bowel habits (constipation or diarrhea)

If you have any of these symptoms, talk to your health care provider. These symptoms may be caused by something other than cancer. But, the only way to know what is causing them is to see your health care provider.

How does colorectal cancer affect people in the U.S.?

Of cancers that affect both men and women, this cancer is the second leading cancer killer in the U.S. In 2005, the Centers for Disease Control and Prevention (CDC) reported that 141,405 adults were diagnosed with colorectal cancer. They reported that 53,005 adults died of the disease in the United States.

What is cancer screening?

Screening is using a test to look for a disease before there are any symptoms. Cancer screening tests, including those for colorectal cancer, detect cancer early or find pre-cancerous polyps that can be removed. Finding cancer early can lead to more effective treatment.  Diagnostic tests, on the other hand, are used when a person has symptoms. They are used to find out what is causing the symptoms. 

What are polyps?

Although most polyps are benign (non-cancerous), a small percentage may contain an area of cancer or may develop into cancer later on. Colon cancer is the second-leading cause of cancer-related deaths in the United States. We know that 150,000 patients develop colon cancer in this country each year with 50,000 deaths resulting, and yet colon cancer is among the most preventable of all cancers.


Colon cancer almost always begins as a benign colon polyp. In 10 to 15 years this polyp may slowly change into cancer – this is why most patients are told to have a colonoscopy at least every 10 years. Polyps are easily discovered and removed as part of a regular screening program. As a direct result of screening programs, the number of people that develop colon cancer in the United States is dropping by 2 percent per year, a major victory over cancer. 


Please follow all of your instructions and drink all of your prep. Polyps or abnormalities can be easily missed if your colon isn’t entirely cleaned out.

Types of Colorectal Cancer Screenings


What are the screening tests for colorectal cancer?

UW Health suggests colorectal cancer screening for men and women starting at age 50 using optical colonoscopy or virtual colonoscopy.




In addition to optical and virtual colonoscopies, flexible sigmoidoscopy is available for screening. Immunochemical Fecal Occult Blood Test (iFOBT) is used to detect blood in the stool. Talk to your health care provider about which test or tests are right for you.

  • Optical colonoscopy (screens entire colon): The rectum and total colon are looked at using a flexible tube with a built in camera and light. The patient is sedated. This tube is called a colonoscope. Growths that are not normal can be found and removed or biopsied. How often: Every 10 years.
  • Virtual colonoscopy (screens entire colon): A CAT scan of the abdomen is done while carbon dioxide is put into the colon. Special computer software builds a 3-D model of the total colon and rectum. This is viewed by a radiologist to look for colon polyps and cancer.  How often: Every 5 years.
  • Flexible sigmoidoscopy (screens part of the colon): A flexible, lighted tube (endoscope) is used to view the lining of the lower third of the colon and rectum. How often: Every 5 years.
  • iFOBT (does not screen the colon): This test checks for unseen blood in the stool. The test can be done at your clinic or at home. You collect a stool sample on a stick and return the stick to the lab at your clinic, or mail the stick to your health care provider's lab if done at home. If blood is found in the stool, more testing is needed. How often: Once a year.


How do I know which screening test is right for me?


At this time, data do not suggest that there is a single "best test" for any one person. Each test has advantages and disadvantages. Patients and their health care providers are encouraged to discuss the benefits and potential risks associated with each screening option as they decide which test to use and how often to be tested. Which test to use depends on:

  • Your preferences
  • Your medical condition
  • The likelihood that you will have the test
  • The resources for testing and follow-up
  • Your risk for colorectal cancer

Getting Ready for a Colorectal Cancer Screening


How do I prepare for a colonoscopy?

The health care provider will give you instructions to read carefully a few days before the exam. You may need to shop for special supplies and get laxatives from a drugstore. Many people think the bowel preparation (often called the "bowel prep") the most unpleasant part of the test. You will follow a special diet the day before the exam. You will need to take a very strong laxative before the exam. Sometimes enemas are needed to clean out the colon. The key to getting good pictures during the exam is to have the colon cleaned out. 

What if I feel sickwhile I am drinking my prep?

We instruct you to drink one glass (about eight ounces) every 10 to 20 minutes but slow down or stop for 30 minutes if you begin to have nausea or abdominal discomfort. It is okay to take a break if necessary; however, it is important to begin taking your prep again when you feel better. It is important to drink all of your solution to increase the likelihood of having a clean colon. 

Will I get dehydrated?

Keep drinking clear liquids until 3 hours before your appointment time. Drinking clear liquids can prevent dehydration.

Will I need to miss work? Will I need someone to drive me home?

Because optical colonoscopy is most often done with drugs that make a patient drowsy, you will need to have someone drive you home. People often will miss a day of work after an optical colonoscopy. Virtual colonoscopy does not require having someone drive you, or missing a day of work because drugs that make a person drowsy (sedation) are not used. If the virtual colonoscopy shows polyps and they need to be removed through optical colonoscopy, then you may miss part of a day of work. For the flexible sigmoidoscopy exam and iFOBT, you do not need a driver or to miss any days of work because sedation is not used. 

What can I expect during my procedure?

When you arrive, a nurse will talk with you about your medical history, take your blood pressure, and place an intravenous (IV) line in your arm. The IV allows us to give you medicine as needed during the procedure to help keep you comfortable and relaxed.


Before the exam, a doctor will talk with you about the test, explain the risks and benefits, and ask you to sign a consent form. Although complications are rare, there is a small risk of problems such as bleeding, creation of a small tear or hole in the intestine, or inflammation of the vein used for IV medication. The doctor will explain these and other risks in full and answer any questions you may have.


Once you are in the procedure room, you will receive medicine through the IV, which will make you feel drowsy. Your procedure will then begin. Most patients report very little discomfort during colonoscopy. If you feel very uncomfortable or anxious, please speak up and more medication can usually be given. Once your colon has been carefully examined, the doctor will remove the instrument and your test will be over. For most patients, colonoscopy takes about 30 minutes.

What happens if a screening test shows an abnormality?

If a screening test finds a problem, more tests may be needed. These tests may include x-rays of the gastrointestinal tract, sigmoidoscopy, or, most often, colonoscopy.


If the iFOBT is positive you will need a follow-up colonoscopy. 


If an abnormality is found during a sigmoidoscopy, a biopsy or removal of a polyp may be done during the test. 


An optical colonoscopy may be recommended. If an abnormality is found during a standard colonoscopy, a biopsy or removal of the polyp is done to find out if cancer is present and remove any polyps. 


If an abnormality is found during a virtual colonoscopy, most patients would be referred for an optical colonoscopy the same day.

Is colorectal cancer screening covered by insurance?

Most insurance plans help pay for colorectal cancer screening tests for people aged 50 or older. Many plans also help pay for screening tests for people younger than 50 who are at increased risk for colorectal cancer. Check with your health insurance provider to find out about your colorectal cancer screening benefits. For questions about coverage for virtual colonoscopy contact the Virtual Colonoscopy Office.

What are the Medicare Preventive Service benefits for colorectal cancer screening?

People with Medicare who are aged 50 or older are eligible for colorectal cancer screening. Medicare will cover some virtual colonoscopy exams if specific criteria is met.  For questions about coverage for virtual colonoscopy contact the Virtual Colonoscopy Office. For more information about Medicare's coverage related to colorectal cancer screening, call the Centers for Medicare and Medicaid Services at 1-800-MEDICARE (1-800-633-4227) (TTY users should call 1-877-486-2048) or visit the Medicare Web site.


Information taken from the Centers for Disease Control and Prevention (CDC) with supplemental information from the National Institutes of Health (NIH), American Cancer Society (ACS), and UW-Health Preventive Health Guideline.