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A stool test is one of many tests used to look for colorectal cancer. These tests may find cancer early, when treatment works better. Colorectal cancer affects the large intestine (colon) and the rectum.
There are two kinds of stool tests used in Canada. The specific test used depends on the guidelines in your province.
Blood in the stool may be the only symptom of colorectal cancer, but not all blood in the stool is caused by cancer. Other conditions that can cause blood in the stool include:
A stool test is one of many tests that may be used to screen for colon cancer. Other tests include sigmoidoscopy, colonoscopy, and CT colonography. Which screening test you choose depends on your risk, your preference, your doctor, and what tests are available in your area. Some tests may not be covered under your provincial health care plan. Talk to your doctor about what puts you at risk and what test is best for you.
Stool tests are done to look for blood in the stool, since cancer in the colon or polyps in the colon are more likely to bleed than normal colon tissue. One type of stool test, the fecal immunochemical test (FIT), checks the stool for microscopic amounts of blood. If the test is positive for blood in the stool, it is important to have a colonoscopy. This will help your doctor find the source of the blood and remove polyps if they are found.
Since colorectal cancers do not bleed all the time, some stool tests may be done over several days on different stool samples. This increases the chance of finding blood in your stool if it exists. The instructions that come with the home test kit will tell you whether to take one sample or several samples over several days.
Do not do the stool tests during your menstrual period or if you have active bleeding from hemorrhoids. Also, do not test a stool sample that has been in contact with toilet bowl cleaning products, including those that turn the water blue.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).
The test kit contains the things you need to collect small samples of stool. For some types of FIT, you may need to collect a stool sample on 2 or more days.
The FIT test doesn't require a special diet in the days before you take the test.
When the test is done, follow the instructions to return the test. Some tests provide the results right away. If your test shows that blood was found, call your doctor as soon as possible.
This test is not done in Alberta.
You may find it unpleasant to collect a stool sample for these tests.
There is no risk from the stool test itself. For this test, you put a sample of stool on a card or you collect a stool sample. Or you may collect the entire stool.
But there are some important things to think about. If your test is positive, you will need to have a colonoscopy. This would be used to see if the stool test result is from colorectal cancer. But blood in the stool is more often caused by something other than cancer. These other causes could include hemorrhoids, ulcers, or taking aspirin. A positive test result could lead you to worry. And you might have a colonoscopy that you didn't need.
If your test sample is sent to a lab or returned to your doctor's office, your test results will likely be read by your doctor. Some labs may send you the results. And depending on the type of test you choose, you may be able to see the results after completing the last step.
A normal FIT test means that there was no blood in your stool at the time of the test. Normal test results are called negative.
An abnormal FIT test means that there was some blood in your stool at the time of the test. Abnormal test results are called positive.
If a stool test is normal, it does not always mean colorectal cancer or colon polyps are not present. That's because these tests can miss polyps and some cancers.
Talk with your doctor about how often you should do a test, depending on your age and any risk factors you may have for colorectal cancer.
A colon polyp, a precancerous polyp, or cancer can cause a positive stool test. With a positive test, there is a small chance that you have colorectal cancer.
Talk with your doctor about what test you may need next. Most of the time, an abnormal stool test means that you will need to have a colonoscopy.
Reasons you may not be able to have a stool test or why the results may not be helpful include:
Some tests for colorectal cancer screening may not be available in all areas. Check with your doctor to find out what tests are used in your area.
Other Works ConsultedHaas JS (2013). Adult preventive health care. In EG Nabel, ed., ACP Medicine, section 2, chap. 2. Hamilton, ON: BC Decker.Leddin D, et al. (2010). Canadian Association of Gastroenterology position statement on screening individuals at average risk for developing colorectal cancer: 2010. Canadian Journal of Gastroenterology, 24(12): 705–714. Also available online: http://www.cag-acg.org/position-statements.Levin B, et al. (2008). Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA: A Cancer Journal for Clinicians, 58(3): 130–160.Nadel MR, et al. (2005). A national survey of primary care physician's methods for screening for fecal occult blood. Annals of Internal Medicine, 142(2): 86–94.Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Adaptation Date: 5/19/2020
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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