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Preparing for Screening Exams

Overview of Test Preparations


Updated August 01, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

If you're the kind of person whose blood pressure kicks up a few notches before a cancer screening test, you're not alone. Anxiety is a common reaction to fear of the unknown. You may be scared of the test itself or the results -- or both. Prolonged anxiety is stressful to your body and can lead to:

  • Restlessness
  • Shaking or trembling
  • Difficulty concentrating
  • Nervousness, jitters
  • Insomnia
  • Interference with personal relationships and career

Arm yourself with knowledge about the different tests for colon cancer screening to decrease your anxiety and increase your mental comfort.

Blood Tests

Photo © A.D.A.M.

Unless you are instructed otherwise, most blood tests do not require any special preparation. A laboratory technician or nurse will draw blood from one of the large veins in your arm and send the specimen for the ordered tests. Blood tests are used to determine the function and health of your major organs, such as your liver, or to check for the presence of tumor markers, such as carcinoembryonic antigen (CEA). Depending on what the doctor ordered, test results can return as early as the following day or up to a few weeks later. You can return to work or normal activities immediately following the test.

Stool Tests

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Your stool may be tested for trace amounts of blood (such as a fecal occult blood or a guaiac test) or for DNA presence. Tumors in the colon sometimes bleed, and they shed specific DNA material (dead cells) that may show up on a stool DNA test. There is no preparation required for a stool test. These tests can be completed in a doctor's office or at home and are a painless process. You will be given a collection kit, which usually consists of a cup or basin to lay over the toilet for stool collection, a test card and instructions on how to complete the specimen collection at home and send it in for processing.


Image © Peterfactors/Dreamstime

X-rays of your colon may include tests known as a double contrast barium enema (DCBE) or a lower gastrointestinal (GI) series. Your doctor may instruct you to take special laxatives to clean out your colon prior to the test. This removes the stool and waste from your colon so that the radiologist can clearly see your bowels. You need to inform your doctor immediately if you think there is a chance you may be pregnant. If you are of childbearing age, you may require a pregnancy blood test prior to the test.

Computed Tomography (CT)

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CT exams do not require any special preparations unless the doctor plans on taking a biopsy specimen of your liver or lung during the exam (called a CT with core needle biopsy) or if you have an allergy to the contrast agent. If your doctor plans on performing a biopsy, your doctor or nurse will instruct you not to eat or drink for six hours prior to the test. If you are allergic to contrast agents, iodine or seafood, your doctor may choose to give you a prescription for medication to be taken prior to the test to mitigate any adverse effects. Most adults can return to work immediately following a CT exam.

Magnetic Resonance Imaging (MRI)

Image © Melissa Connors/Dreamstime

An MRI may be ordered to better visualize structures in your lower abdomen, such as your colon, rectum or adjacent organs (stomach, bladder, ovaries). There is no preparation at home for the test, unless otherwise instructed. The MRI has strong magnetic fields and certain people cannot have an MRI, including those who have:

  • A pacemaker or other implanted device
  • Shrapnel
  • Jewelry that cannot be removed
  • Stents, wires, rods or metal clips in their body
  • Claustrophobia

You will be required to complete an MRI screening form and change into a gown without metal buttons or zippers for the test, which usually takes about 45 minutes. You can go back to regular activities immediately after an MRI.


Image © A.D.A.M.

Sigmoidoscopy and colonoscopy (including the virtual colonoscopy) require preparation at home in the days prior to the test. You will need to complete a bowel preparation, which entails using a combination of laxatives, enemas or sometimes even a special diet to cleanse your bowels. Your doctor will instruct you to stop eating and drinking about six hours before the test time. Make sure you have arranged for someone to drive you home, as the nurses will not let you drive home yourself after receiving sedation. In most cases, you will be allowed to resume normal activities within 24 hours. The exception to this rule is the virtual colonoscopy, which doesn't require sedation. You can return to work immediately following a virtual colonoscopy.


American Cancer Society. (2006). American Cancer Society's Complete Guide to Colorectal Cancer. Clifton Fields, NE: American Cancer Society.

American Cancer Society. (n.d.). Can Colorectal Polyps and Cancer be Found Early? Accessed July 25, 2012.

University of California, San Francisco. (n.d.). How to Prepare for a Magnetic Resonance Imaging (MRI). Accessed July 25, 2012.

University of Rochester Medical Center. (n.d.). Anxiety Disorder. Accessed July 25, 2012.

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  4. Colon Cancer Screening and Tests
  5. Preparing for Screening Exams in Colon Cancer

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