Acute and chronic diarrhea. How to keep laboratory testing to a minimum.

Diagnosing a cause of diarrhea is a challenging undertaking but can be accomplished if a systematic approach is used for evaluation. Pathophysiologic mechanisms of acute diarrhea (eg, Giardia lamblia infection, antibiotic use) are different from those of chronic diarrhea (eg, secretory dysfunction from thyrotoxicosis, lactose or fructose intolerance), so adequate history taking and physical examination are essential in narrowing the diagnosis. Laboratory investigation can then be directed using the information obtained, and the cause of the diarrhea can be established without subjecting the patient to extensive and expensive testing. Undoubtedly, some functional entities that contribute to diarrhea await discovery.