The Curbsiders Internal Medicine Podcast #267 Diarrhea Disemboweled Part 2: Chronic Diarrhea with Dr. Iris Wang
Apr 7, 2021
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Stool Osmotic Gap Simplifies Diarrhea Types
- Use the stool osmotic gap to separate osmotic from secretory diarrheas early in evaluation.
- A large gap implies unmeasured osmoles (sugar alcohols, malabsorbed carbs, laxatives) driving osmotic diarrhea.
Ask If Diarrhea Stops With Fasting
- Ask whether the diarrhea resolves with fasting because true osmotic diarrhea stops when patients fast.
- Use this simple history question early to narrow the differential and target testing.
Check Stool pH If Osmotic Gap High
- Measure stool pH when the osmotic gap is high to evaluate for carbohydrate malabsorption.
- A low stool pH suggests bacterial fermentation of unabsorbed carbohydrate in the colon.