Suggested approach to the evaluation of chronic diarrhea in adult patients in resource-rich settings

TSH: thyroid-stimulating hormone; ESR: erythrocyte sedimentation rate; CRP: C-reactive protein; IBD: inflammatory bowel disease; IBS: irritable bowel syndrome; HIAA: hydroxy indole acetic acid.
* Serum electrolytes should be evaluated in patients with severe diarrhea, or when there is concern for dehydration or electrolyte abnormalities.
¶ Refer to appropriate UpToDate topic on chronic diarrhea.
Δ Empiric therapy may be appropriate when comorbidities limit diagnostic evaluation or when a diagnosis is strongly suspected (eg, lactose restriction for suspected lactose intolerance, bile acid binding resin for post-cholecystectomy diarrhea).
◊ Additional laboratory studies to assess for malabsorption include albumin, red cell folate, serum iron, total iron binding capacity, vitamin B12, calcium, magnesium, carotene, and 25-hydroxyvitamin D.
§ In patients with abdominal pain as a major symptom, systemic symptoms (eg, fever, weight loss), or suspected Crohn or pancreatic disease we perform additional abdominal imaging with an abdominal computed tomography or magnetic resonance imaging.