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  • Dr Paul Dhillon MBBCH CCFP

The Dirty Secret: Diarrheal illnesses – What’s the Diff?

The Merriam Webster dictionary defines diarrhea as an illness that causes you to pass waste from your body very frequently and in liquid rather than solid form. Knowing only that is not enough to pass the Family Medicine examination. The Review Course in Family Medicine reviews the key features of diarrhea that you need to know for the exam.


Could it be HIV or Immunosuppression? These are not typically at the top of your differential but that’s a key thing to rule out in a patient with chronic diarrhea. Remembering key but simple things like that is what The Review Course is for. It will improve your exam performance and your future practice.

Here are The Review Course in Family Medicine’s own 7 Dirty Diarrhea Tips.

  • Dehydration – Assess & Treat! How dehydrated are they? What is the appropriate rehydration strategy? Have you considered PO rehydration (i.e. oral rehydration solution) before necessarily starting an IV?

  • Infectious – Where have they been travelling? Any sick contacts? Could they pass it on to anyone else? Could it be HIV?

  • Antibiotics – Could it be C. Difficile?

  • Red Flags – RED blood in the stools, nocturnal defecation, fever, unintended weight loss, anemia.

  • Extraintestinal manifestations – If the history sounds like the diarrhea is caused by IBD, do they have arthritis? Iritis? Erythema nodosum? Aphthous Ulcers?

  • Elderly – Could it be something more sinister? Consider investigating earlier than you usually might.

  • Antibiotics – Are they necessary? If it’s a viral diarrhea then they could be doing more harm than benefit.


Diarrhea is a simple topic at first glance but it’s a great way to test you on Travel Medicine, Diarrhea, Infectious Diseases, Dehydration, Gastroenterology, and Occupational Health all in one. Don’t forget these crucial management items for any of these topics (and for many other Family Medicine examination topics):

  • Mandatory Reporting - “Notify Public Health” as part of your management of someone with infectious diarrhea who is working as a food handler or if you think they are involved in a larger community or hospital outbreak.

  • See our other blog post on Mandatory Reporting

  • Occupation AND impact - ALWAYS ask about occupation when taking a history on the exam. And, for bonus points, ask HOW the illness is interfering with their occupation.

  • Contagiousness – Provide advice on whether the patient should be kept home from work or school, AND for how long


Parents of young children with diarrhea might ask you about the use of bismuth subsalicylate (Pepto-Bismol type preparations) or zinc in treating acute diarrhea. What would you say to them in the Canadian context?

In two great Child Health Updates in the Canadian Family Physician journal, Dr. Goldman from the UBC Department of Pediatrics gives the diarrhea down-low on these questions.

“Studies conducted in developing countries found the use of bismuth subsalicylate for diarrhea was effective in shortening the duration of illness; however, despite these findings, potential risks of Reye syndrome and compliance challenges inhibit recommendations to use bismuth subsalicylate in children with diarrhea.”

“Zinc supplementation for diarrhea in children is a safe and effective measure to shorten the illness and to reduce other complications including death. While the World Health Organization recommends a daily dose of 10 to 20 mg of zinc (based on age) for 10 to 14 days for management of acute diarrhea, Canadian children who eat a regular diet do not need such supplementation.”

If you’re still reading down here and haven’t signed up for the course yet, have a read of a great CMAJ Practice article about when to test and when to treat a possible infectious diarrhea.

If you want to save the reading and learn what you need to know for the exam, sign up now!


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2 - Ran D. Goldman. Practice - Child Health Update. Bismuth salicylate for diarrhea in children. Can Fam Physician August 2013 59: 843-844.

3 - Ran D. Goldman. Practice - Child Health Update. Zinc supplementation for acute gastroenteritis. Can Fam Physician April 2013 59: 363-364.

4 – Hatchette, TF and Farina, DF. Infectious diarrhea: when to test and when to treat. CMAJ February 22, 2011 vol. 183 no. 3 First published December 20, 2010.

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