Stool Tests for Colorectal Cancer
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
There are three kinds of stool tests:
- Fecal occult blood test (FOBT). For this test, you put tiny samples of your stool on a special card or cloth and send it to a lab. The lab uses chemicals to find blood that can't be seen with the naked eye. With some test kits, you can add the chemicals yourself at home. For several days before the test, you can't eat certain foods, and you have to stop taking some medicines.
- Fecal immunochemical test (FIT), also called an
immunochemical fecal occult blood test (iFOBT). For this test, you take a sample with a brush and dab it onto a special card. This test may be easier to do at home than the FOBT. There are no drug or food restrictions, and collecting a stool sample may take less effort.
- Stool DNA test (sDNA). Instead of looking for blood in the stool, this test looks for abnormal DNA from cancer or polyp cells. For this test, you collect all of the stool from one bowel movement and put it in a special box that you mail to the lab. There are no drug or food restrictions. Of the three tests, this one has the easiest instructions.
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:
- Hemorrhoids .
These are enlarged, swollen veins in the anus. Hemorrhoids can form inside
the anus (internal hemorrhoids) or outside of the anus (external
- Anal fissures. These are thin tears in
the tissue that lines the anus (anal sphincter) up into the anal
- Colon polyps. These growths of tissue are attached to the colon and often look like
a stem or stalk with a round top.
- Peptic ulcers. These sores
form when the digestive juices made in the stomach eat away at the lining of
the digestive tract.
- Ulcerative colitis. This type of
inflammatory bowel disease (IBD) causes inflammation and sores
(ulcers) in the inner lining of the colon and rectum.
- Gastroesophageal reflux disease (GERD). This is the
abnormal backflow (reflux) of food, stomach acid, and other digestive juices
into the esophagus.
- Crohn's disease. This type of inflammatory bowel disease causes inflammation and
ulcers that may affect the deep layers of the lining of the digestive
- Use of aspirin or
nonsteroidal anti-inflammatory drugs (NSAIDs).
Stool tests may be used to check for
colorectal cancer, but they are never used to diagnose it. Other tests
for colorectal cancer include flexible
CT scan (virtual colonoscopy).
A stool test is one of many tests that may be used to screen for colon cancer. Other tests include sigmoidoscopy, colonoscopy, and computed tomographic colonography. Which screening test you choose depends on your risk, your preference, and your doctor. Talk to your doctor about what puts you at risk and what test is best for you.
- Colon Cancer: Which Screening Test Should I Have?