Skip to content
My WebMD Sign In, Sign Up

Colorectal Cancer Health Center

Font Size

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 camera.gif) and the rectum.

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 camera.gif. These are enlarged, swollen veins in the anus. Hemorrhoids can form inside the anus (internal hemorrhoids) or outside of the anus (external hemorrhoids).
  • Anal fissures. These are thin tears in the tissue that lines the anus (anal sphincter) up into the anal canal.
  • 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 tract.
  • 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 sigmoidoscopy, colonoscopy, and 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?

WebMD Medical Reference from Healthwise

Last Updated: October 30, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Today on WebMD

colorectal cancer slideshow
SLIDESHOW
what is your cancer risk
HEALTH CHECK
 
Colon Cancer Survival
VIDEO
Kemeny Chemo Side Effects
VIDEO
 

bread
ARTICLE
Colon vs Rectal Cancer
VIDEO
 
New Colorectal Treatments
VIDEO
can lack of sleep affect your immune system
FEATURE
 

Cancer Facts Quiz
QUIZ
Virtual Colonoscopy
VIDEO
 
Picture of the Colon
ANATOMY
Vitamin D
SLIDESHOW
 

WebMD Special Sections