Stool Test: Fecal Blood

What It Is

A stool (feces) sample can provide doctors with valuable information about what's going on when your child has a problem in the stomach, intestines, rectum, or other part of the gastrointestinal (GI) system. One of the most common reasons to collect a sample is to determine if there's blood in the stool.

Sometimes harmful bacteria or parasites can cause a variety of conditions, such as bloody diarrhea. It may be necessary to examine the stool under a microscope and perform other tests to find the cause of the problem.

To test the stool for the presence of blood, a noninvasive test called the fecal occult blood test (FOBT) is performed. The test detects hidden (occult) blood in the stool — blood that cannot be seen by the naked eye. Blood may come from any part of the digestive tract, from the esophagus to the anal area. Sometimes, blood detected in the stool can come from swallowed blood if the child has had bleeding from the mouth, throat or nose.

Why It's Done

A doctor may request a fecal occult blood test to look for blood that's present due to causes such as:

allergies or inflammation
gastrointestinal infection caused by bacteria, viruses, or parasites
bleeding in the GI tract from ulcers and other problems
polyps

Preparation

Unlike most other lab tests, a stool sample is often collected by parents at home, not by health care professionals at a hospital or clinic.

For a week before the test, your child may be asked to avoid certain foods and medications such as:

aspirin
anti-inflammatory drugs such as ibuprofen
vitamin C supplements

Procedure

The doctor or hospital laboratory will usually provide written instructions on how to collect a stool sample.

If instructions aren't provided, here are tips for collecting a stool sample from your child:

Be sure to wear latex gloves and wash your hands and your child's hands afterward.
Many kids with diarrhea, especially young kids, can't always let a parent know in advance when a bowel movement is coming. So a hat-shaped plastic lid is used to collect the stool specimen. This catching device can be quickly placed over a toilet bowl, or under your child's bottom, to collect the sample. Using a catching device can prevent contamination of the stool by water and dirt. Another way to collect a stool sample is to loosely place plastic wrap over the toilet seat. Then place the stool sample in a clean, sealable container before taking it to the lab. Plastic wrap can also be used to line the diaper of an infant or toddler who isn't yet using the toilet.
The stool should be collected into clean, dry plastic jars with screw-cap lids. Your child may be asked to provide a stool sample one or more times. For best results, the stool should be brought to the lab right away. If this isn't possible, the stool should be refrigerated and then taken to the lab as soon as possible.

What to Expect

When the sample arrives at the laboratory, it's checked for blood by placing a smear of the stool on special paper. A chemical solution called guiac is then placed on the paper with the stool smear. If the paper turns blue, this means there's blood in the stool.

Getting the Results

In general, the result of the fecal occult blood test is reported within a day.

Risks

No risks are associated with collecting stool samples.

Helping Your Child

Collecting a stool sample is painless. Tell your child that collecting the stool won't hurt, but it has to be done carefully. A child who is old enough might be able to collect the sample alone to avoid embarrassment. Instruct your child how to do this properly.