What is a white blood cell (WBC) in stool test?

This test looks for white blood cells in a sample of your stool (poop). White blood cells are also called leukocytes, so this test is sometimes called a leukocytes in stool test.

White blood cells are part of your immune system. They help your body fight off infections and other diseases. White blood cells in your stool are usually a sign that you have an infection or other condition in your digestive system that's causing inflammation.

A white blood cell in stool test is used if you have diarrhea that could be caused by inflammation. Diarrhea from inflammation is severe and lasts for more than a couple days. It can include blood in stool, abdominal (belly) pain, and fever. It may be caused by:

• Certain bacterial infections, such as:
  • Clostridium difficile (C. diff). This infection mostly happens after taking antibiotics that kill the "good germs" that keep C. diff bacteria from growing in your body.
  • Some types of bacteria that cause "food poisoning," including:
    • Salmonella. Most infections come from contaminated food, but you can get salmonella from infected animals, especially reptiles and birds.
    • Shigella. Infection with shigella is called shigellosis. You can get it from food and touching contaminated surfaces and then touching your mouth.
    • Campylobacter. Infection can happen from food and contact with dog and cat feces (poop).
• Inflammatory bowel disease (IBD), which includes:
  • Ulcerative colitis
  • Crohn's disease
• A parasite (Entamoeba histolytica) which causes a disease called "amebiasis." Amebiasis is most common in tropical places with poor sanitary conditions.

A white blood cell in stool test can't diagnose the exact condition that's causing diarrhea. But it can help narrow down the possible causes to conditions that either do or don't involve inflammation.

Other names: leukocytes in stool, stool WBC, fecal WBC, fecal leukocyte test, FLT, FGST, fecal leukoctye gram stain screen

What is it used for?

A white blood cell in stool test is used to find out whether diarrhea is caused by conditions that involve inflammation in the digestive system.

It's mainly used for people who have diarrhea symptoms that suggest inflammation. These symptoms include:

• Watery diarrhea three or more times a day that doesn't get better after several days
• Abdominal (belly) cramps and/or pain
• Blood and/or mucus in stool
• Fever
• Fatigue
• Weight loss

A white blood cell in stool test can't diagnose the condition that's causing diarrhea, so it's often used with other tests.

Why do I need a white blood cell in stool test?

Most diarrhea goes away on its own after a day or two, and your health care provider doesn't need to find the cause. But you may need a white blood cell in stool test and other tests if you have symptoms of diarrhea from inflammation that don't improve after a few days.

Knowing the cause of your diarrhea helps your provider choose the right treatment. That's important because ongoing diarrhea can lead to serious health problems, including dehydration and electrolyte imbalances.

See your provider right away if you have:

• Signs of dehydration, including dry mouth, dark urine (pee), fatigue, or dizziness
• Diarrhea for more than 2 days, or for more than 24 hours in a young child or infant
• A fever of 102 degrees or higher
• Severe pain in the abdomen (belly) or rectum
• Stool that is black and tarry or contains blood or pus
• In adults: frequent vomiting or diarrhea 6 or more times in 24 hours

What happens during a white blood cell in stool test?

You will need to provide a stool sample for your test. Your provider will probably give you a container or kit with instructions on how to collect the sample. There are different ways to collect stool samples, so follow the instructions carefully. In general, you'll need to:

• Label the container with your name, the collection date, and time.
• Collect a stool sample as instructed. This usually involves using a clean, dry container, or special paper or plastic wrap placed over the toilet to catch the stool.
• Make sure the stool doesn't mix with any urine, toilet paper, or water from the toilet.
• Close the container tightly.
• Wash your hands well with soap and water.
• Return the container according to the instructions.

If you're collecting a sample from diapers, you'll get special instructions for using plastic wrap inside of a clean diaper. In certain cases, a provider may use a swab to take a stool sample from the rectum.

Will I need to do anything to prepare for the test?

Certain medicines and foods may affect the test results. Ask your provider if there are any specific things you need to avoid before the test.

Are there any risks to the test?

There is no known risk to having a white blood cell in stool test.

What do the results mean?

A positive or abnormal test result means that white blood cells were found in your stool sample. That means you have inflammation in your digestive tract. This information helps rule out conditions that don't cause inflammation, including viral infections, certain bacteria, and most parasites. Other tests can help find out what is causing your illness.

A negative or normal test result means that no white blood cells were found in your stool sample. That may mean that inflammation isn't causing your illness. But a normal test result can't rule out conditions that cause inflammation. That's because white blood cells don't last long in a stool sample.

If your stool sample contained a small number of cells that broke apart during testing, they may not show up. So, you could have inflammation in your digestive system even though your test didn't find any white blood cells in your stool.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a white blood cell in stool test?

Instead of a white blood cell in stool test, your provider may order a more accurate test to check for inflammation in your digestive system. It's called a calprotectin fecal test. Calprotectin is a protein that certain white blood cells release in the intestine when there is inflammation.