What
Is a Fecal Occult Blood Test?
IN
THIS ARTICLE
A
test for fecal occult blood looks for blood in your poop, or
feces. It can be a sign of a problem in your digestive system, such as a growth, or
polyp, or cancer in the colon or rectum.
If
the results show that there is blood (whether you can
see it or not), it’s important for your doctor to find the source of bleeding
to diagnose and treat the problem.
What Causes Blood to
Appear in Poop?
Blood
may show up in your poop because of one or more of the following conditions:
- Growths or
polyps of the colon
- Hemorrhoids (swollen blood vessels near
the anus and lower rectum that can
rupture, causing bleeding)
- Anal fissures (splits or cracks in the
lining of the anal opening)
- Intestinal
infections that cause inflammation
- Ulcers
- Ulcerative colitis
- Crohn's disease
- Diverticular
disease, caused by outpouchings of the colon wall
- Problems
in the blood vessels in the large intestine
- Meckel’s
diverticulum, usually seen in children and young adults
Gastrointestinal
bleeding may be microscopic, so you can’t see it. (Doctors call that “occult”
blood.) Or you may easily see it as red blood, or black tar-like bowel movements.
How Do I Take a Fecal
Occult Blood Test?
There
are different kinds of these tests. You can buy some kits at the pharmacy. Or
your doctor may give you a home test kit at one of your appointments. They come
with instructions. Most list a phone number to call if you have questions.
For
some tests, you put a special pad or tissue from the kit into the toilet and
tell your doctor if it changes color.
Other
tests require you to collect stool samples on more than one day. You then send
the samples, in a special container and envelope, directly to your doctor's
office for analysis with a microscope or chemicals. You should use newer “high
sensitivity” versions of these tests.
What Should I Do to
Prepare?
You
don’t have to “cleanse” your colon like you would before a colonoscopy. But you do need to
follow the instructions carefully. Don’t take the test if you have:
- Diarrhea
- Colitis
- Constipation
- Diverticulitis
- Ulcers
- Hemorrhoid flare-ups
- Your
period
Because
certain foods can alter some of the tests’ results, don’t eat these foods for 48
to 72 hours before you take the test:
- Beets
- Broccoli
- Cantaloupe
- Carrots
- Cauliflower
- Cucumbers
- Grapefruit
- Horseradish
- Mushrooms
- Radishes
- Red meat
(especially meat that is cooked rare)
- Turnips
- Vitamin C-enriched foods or beverages
You
may need to stop taking certain medicines 48 hours before the test. Ask your
doctor about that.
What Do the Fecal Occult
Blood Test Results Mean?
If
you have a positive result, that means that it showed blood in the stool. (In this case,
“positive” is not necessarily good!)
You’ll
then need to get tests to find out where the blood came from. Your doctor may
recommend a colonoscopy, and an upper gastrointestinal
endoscopy to
see if the bleeding is coming from the stomach or small intestine.
If these don’t show the source, you may need to swallow a small capsule that
takes pictures as it passes through your intestines. It may see areas of bleeding
not shown by other tests, especially in the small intestine.
A
negative test result means that no blood was found in the stool sample during
the testing period. You should continue to follow your doctor's recommendations
for regular cancer checks.
How Often Do I Need to
Have a Fecal Occult Blood Test?
You
don’t have to take these tests. There are other methods -- such as colonoscopy
(in which the doctor uses a flexible tube with a tiny camera on it to check
your entire colon); CT colonography (also called a virtual colonoscopy, which
is a CT scan of your colon); and
tests that check your poop for cancer DNA.
If
you decide you want to take fecal occult blood tests, you’ll need to do that
every year, and also get other tests by your doctor -- flexible sigmoidoscopy(like a colonoscopy but
doesn’t go as far into your digestive system) and barium enema (X-rays of the
colon after you get an enema made with barium) -- every five years to check for
colorectal polyps or cancer.
Remember,
if the test shows signs of blood, you’ll probably still need to get a
colonoscopy.
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