Chronic diarrhea is defined by duration (greater than four weeks) and can be further characterized by steatorrhea (pathologic fat malabsorption, classically defined by a quantitative fecal fat threshold) arising from mucosal or pancreatic/biliary dysfunction, with diagnostic evaluation organized around stool studies, osmolar gap calculation, malabsorption testing, and endoscopic/radiologic assessment. Infectious bacterial diarrhea is classified along two axes—invasive versus non-invasive/toxigenic, and the presence versus absence of fecal leukocytes—which corresponds to mechanistically distinct pathogen categories (invasive mucosal pathogens vs. toxin-mediated secretory pathogens). This concept belongs to gastroenterology, specifically the diagnostic classification of chronic and infectious diarrheal disease.
Chronic diarrhea is defined by duration (greater than four weeks) and can be further characterized by steatorrhea (pathologic fat malabsorption, classically defined by a quantitative fecal fat thresh…