 |
|
| ||||||||||||||||||||||||||
|
|
| ||||||||||||||||||||||||||
|
|
|
|
|
| ||||||||
Fecal occult blood is a term for blood present in the feces that is not visibly apparent. In medicine, a fecal occult blood test is a check for hidden (occult) blood in the stool (feces). More accurately, the test looks for heme.
Fecal occult blood testing - as its name implies - can prove clues as to subtle blood loss in the gastrointestinal tract, anywhere from the mouth to the colon. Positive tests warrant further investigation for peptic ulcers or a malignancy (such as colorectal cancer or gastric cancer).
In the event of a positive fecal occult blood test, the next step in the workup is a form of visualization of the gastrointestinal tract (ie: endoscopy, colonoscopy, virtual colonoscopy).
Annual testing may reduce the mortality associated with colon cancer by a third.
There are three methods for measuring heme in feces:
One method: the test involves smearing some feces onto some absorbent paper that has been treated with a chemical. Hydrogen peroxide is dropped onto the paper, if trace amounts of blood are present, the paper will change colour. This method works as hemoglobin has a peroxidase-like effect, rapidly breaking down hydrogen peroxide.
The test is often false-positive (i.e. there is no source of bleeding). This is often due to recent ingestion of under-cooked meats, and a patient is generally advised to keep a meat-free diet for several days before handing in the feces sample.
False negatives may result if the patient has been taking vitamin C supplements.
The test is more sensitive if the sample is hydrated before testing. However, the specificity is decreased in this method.
An estimated 1-5% of the tested population have a positive fecal occult blood test. Of those, about 2-10% have cancer, while 20-30% have adenomas.
Causes for a positive test are:
|
||||
| View Live Article | This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License | |
||
