Diarrhea in Adults - Chronic

Definition

Chronic diarrhea in adults is defined as the passage of loose or watery stools lasting more than four weeks, often reflecting underlying functional, infectious, inflammatory, or systemic disorders.

Epidemiology

• Prevalence varies globally, more common in adults >50 years
• Functional diarrhea and IBS-D are frequent causes in developed countries
• Infectious, malabsorptive, and inflammatory causes are more common in developing regions
• Affects both sexes, with slight female predominance in functional diarrhea
• Chronic diarrhea significantly affects quality of life and work productivity

Etiology

• Functional: IBS-D, functional diarrhea without IBS
• Inflammatory: IBD (Crohn’s disease, ulcerative colitis)
• Infectious: chronic infections (Giardia, C. difficile, parasitic infections)
• Malabsorptive: celiac disease, lactose intolerance, pancreatic insufficiency, bile acid malabsorption
• Medication-induced: antibiotics, laxatives, NSAIDs, metformin
• Endocrine/metabolic: hyperthyroidism, diabetes mellitus, Addison’s disease, VIPoma

Pathophysiology

• Imbalance between intestinal secretion and absorption leading to increased stool water content
• Inflammation in mucosa increases secretion and motility (IBD, infection)
• Osmotic diarrhea from unabsorbed solutes (lactose, malabsorption syndromes)
• Secretory diarrhea from hormonal or toxin-mediated mechanisms (VIP, gastrinoma, C. difficile toxins)
• Altered gut microbiota and motility disorders contribute to functional diarrhea