Tests and diagnosis

By Mayo Clinic Staff

The cause of your diarrhea may be difficult to diagnose. Even if blastocystis is present on a fecal exam, it may not be causing your 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. Also called an ova and parasite test, this test looks for parasites or their eggs (ova) that cause signs and symptoms, such as diarrhea and abdominal cramping and bloating. Your doctor may ask you for several stool samples, each from a different day.

    Your doctor may give you a special container with preservative fluid for your stool samples. If not, refrigerate your samples until you take them to your doctor's office or the lab your doctor designates. Don't freeze the samples.

  • Endoscopy. If you have symptoms, but the fecal exam doesn't reveal the cause, your doctor may request this test. A doctor, usually a gastroenterologist, inserts a tube into your mouth or rectum to look for the cause of your symptoms. You'll be sedated for this test, and you'll need to fast beginning at midnight the night before the test.
  • Blood tests. Although there are no blood tests that can detect blastocystis, your doctor may order blood tests to look for other causes of your signs and symptoms.
Jan. 25, 2013

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