Pathophysiology of acute diarrhea.

Diarrhea, a major health problem worldwide, is both a sign and a symptom. As a symptom, diarrhea has been described as an increase in stool frequency, an increase in stool volume, and/or a decrease in stool consistency. As a sign, diarrhea is characterized by an increase in stool water excretion to greater than 150 to 200 ml every 24 hours. Four mechanisms that may be responsible for the alterations in fluid and electrolyte movement associated with diarrhea are increased luminal osmolality, decreased fluid absorption, increased intestinal secretion, and altered intestinal motility. Specific pathogenic mechanisms for acute infectious diarrhea include tissue invasion, enterotoxin production, and adhesion of infectious agents to epithelial cells. Antidiarrheal agents remove secretagogues from the intestinal tract, stimulate fluid absorption, and inhibit electrolyte movement.