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Your doctor will want to ask you about your diarrhoea. The frequency, quantity and consistency of bowel movements are very individual. They depend on your metabolism, the foods you eat, your activity level, the amount of fluids you drink, the medications you take, and even any stress that you are experiencing. Your doctor will be looking for changes from your normal habits – things that are out of the ordinary, and for alterations that he or she knows are commonly associated with diarrhoea-causing conditions. Your doctor will be asking you a series of questions that help choose which laboratory tests will be the most useful. These questions may include:

  • What is the frequency of your stools?
  • How long you have been experiencing diarrhoea?
  • What are the consistency, colour and approximate volume of the stools?
  • Is blood or mucus in the stool?
  • What other symptoms are you having: abdominal pain, nausea, fever, headache, fatigue?
  • What and where have you eaten recently?
  • Have you travelled outside Australia recently?
  • Are any of your family members, close acquaintances or co-workers ill?
  • Have you been on antibiotics lately?

Laboratory tests
If your diarrhoea is uncomplicated and goes away within a few days, your doctor may not search for the cause of your gastrointestinal upset. However, if your diarrhoea is severe, if there is blood or mucus present or if it is continuing unabated he or she may request one or more of the following tests. This is especially true if you have been abroad or have eaten or drunk anything that has also made someone close to you ill. Testing may include:

  • Ova and parasite examination. A microscopic examination of your stool for parasites and the ova (eggs, cysts) of parasites.
  • Stool white blood cells. These may be present in the stool when there is a bacterial infection.
  • Stool culture to check for pathogenic gastrointestinal bacteria.
  • Antigen tests for giardia, cryptosporidium and E. histolytica are available but not routinely used in Australia. These tests detect protein structures on the parasites. They are more sensitive and specific for these particular parasites than microscopic examination for them and their ova.
  • Food allergy and intolerance tests (such as tests for lactose intolerance).
  • Coeliac disease tests, such as anti-TTG and anti-endomysial antibodies.
  • Antibody tests for parasites. These are not as useful to detect current infections but may be requested to check for past or chronic infections, especially if unusual parasitic infections are suspected.
  • Rotavirus test, a rapid antigen test.
  • Clostridium difficile toxin, a rapid test used to identify a Clostridium difficile infection by detecting the toxin made by the bacteria.
  • Electrolytes. If you are dehydrated your doctor may want to do a blood test to determine whether your electrolytes have become imbalanced.
  • Biopsy of the small intestines (rarely done) to look for signs of parasitic infection

Non-laboratory tests
Sometimes upper gastrointestinal endoscopy, sigmoidoscopy or colonoscopy are used to look at portions of the gastrointestinal tract.

Last Review Date: January 2, 2018