is occult blood in stool always cancer of colon
Learn more about this top honor. The fecal occult blood test (FOBT) is a lab test used to check stool samples for hidden (occult) blood. Occult blood in the stool may indicate colon cancer or polyps in the colon or rectum â though not all cancers or polyps bleed. Typically, occult blood is passed in such small amounts that it can be detected only through the chemicals used in a fecal occult blood test.