Diagnosis

The cause of your diarrhea might be difficult to diagnose. Even if Blastocystis hominis is found in your stool, it might not be causing your symptoms. More commonly, it suggests you've been exposed to contaminated food or water that contains other organisms that can cause gastrointestinal symptoms.

Your doctor likely will take your medical history, ask you about recent activities, such as traveling, and perform a physical exam. A number of lab tests help diagnose parasitic diseases and other noninfectious causes of gastrointestinal symptoms:

  • Stool (fecal) exam. This test looks for parasites or their eggs. Your doctor might give you a special container with preservative fluid for your stool samples. Refrigerate — don't freeze — your samples until you take them to your doctor's office or lab.
  • Endoscopy. If you have symptoms, but the fecal exam doesn't reveal the cause, your doctor might request this test. After you're sedated, a doctor, usually a gastroenterologist, inserts a tube into your mouth or rectum to look for the cause of your symptoms. You'll need to fast beginning the night before the test.
  • Blood tests. A blood test that can detect blastocystis is available but not commonly used. However, your doctor might order blood tests to look for other causes of your signs and symptoms.

More Information

Treatment

If you have Blastocystis hominis without signs or symptoms, then you don't need treatment. Mild signs and symptoms might improve on their own within a few days.

Potential medications for treating Blastocystis hominis include:

  • Antibiotics, such as metronidazole (Flagyl) or tinidazole (Tindamax)
  • Combination medications, such as sulfamethoxazole and trimethoprim (Bactrim, Septra, others)
  • Anti-protozoal medications, such as paromomycin or nitazoxanide (Alinia)

Response to medication for Blastocystis hominis varies greatly from person to person. And because the organism might not be the cause of your symptoms, improvement might be due to the medication's effect on another organism.

Preparing for your appointment

You'll likely see your primary care doctor. However, in some cases, you might be referred to someone who specializes in either infectious disease or in digestive system disorders (gastroenterologist).

Here's some information to help you get ready for your appointment.

What you can do

Be aware of pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do in advance, such as restrict your diet.

Make a list of:

  • Your symptoms, and when they began
  • Key personal information, including any major stresses or recent life changes and whether you've recently traveled to a developing country
  • All medications, vitamins or supplements you take, including doses
  • Questions to ask your doctor

Questions to ask your doctor include:

  • What's the most likely cause of my symptoms?
  • Are there other possible causes?
  • What tests do I need?
  • What treatments are available, and which one do you recommend for me?
  • Should I change my diet?
  • Are there brochures or other printed material that I can take home with me? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you questions, including:

  • Do you have symptoms all the time, or do they come and go?
  • How severe are your symptoms?
  • Does anything seem to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?
  • Do you have any other health conditions?

What you can do in the meantime

If your symptoms are related to Blastocystis hominis, they'll likely go away on their own before you even see your doctor. Stay well-hydrated. Oral rehydration solutions — available through drugstores and health agencies worldwide — can replace lost fluids and electrolytes.

Jan. 29, 2019
  1. Jameson JL, et al., eds. Protozoal infections. In: Harrison's Principles of Internal Medicine. 20th ed. New York, N.Y.: The McGraw-Hill Companies; 2018. https://accessmedicine.mhmedical.com. Accessed Dec. 8, 2018.
  2. Blastocystis spp. FAQs. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/blastocystis/faqs.html. Accessed Dec. 8, 2018.
  3. Leder K, et al. Blastocystis species. https://www.uptodate.com/contents/search. Accessed Dec. 8, 2018.
  4. Parasites — Nonpathogenic (harmless) intestinal protozoa. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/nonpathprotozoa/biology.html. Accessed Dec. 8, 2018.
  5. Food and water safety. Centers for Disease Control and Prevention. https://wwwnc.cdc.gov/travel/page/food-water-safety. Accessed Dec. 8, 2018.
  6. Avoid foodborne illness when traveling abroad. U.S. Department of Health and Human Services. https://www.foodsafety.gov/blog/international_travel.html. Accessed Dec. 8, 2018.
  7. When & how to wash your hands. Centers for Disease Control and Prevention. https://www.cdc.gov/handwashing/when-how-handwashing.html. Accessed Dec. 8, 2018.
  8. Freedman S. Oral rehydration therapy. https://www.uptodate.com/contents/search. Accessed Dec. 8, 2018.

Related

Associated Procedures