Recurrent Diarrhea: Causes, Evaluation, and Management

Monthly diarrhea suggests a chronic or recurrent condition. Systematic approach:

Common Causes

• IBS-D (diarrhea-predominant): Rome IV criteria; pain related to defecation, change in frequency/form.
• Food intolerances: Lactose, fructose, sorbitol, FODMAPs.
• Celiac disease: Screen with TTG-IgA + total IgA.
• Bile acid malabsorption: Post-cholecystectomy or idiopathic; responds to cholestyramine.
• Microscopic colitis: Watery diarrhea, normal colonoscopy; biopsy diagnosis.
• Medications: Metformin, PPIs, antibiotics, magnesium, SSRIs.
• Endocrine: Hyperthyroidism, Addison's, carcinoid.
• IBD (Crohn's/UC): Usually with blood, weight loss, nocturnal symptoms.

Evaluation

• Stool studies: culture, C. diff, ova/parasites, fecal calprotectin (inflammation marker).
• Blood: CBC, CMP, TSH, celiac serology, B12/folate.
• Breath tests: lactose, fructose, SIBO.
• Colonoscopy with biopsies if alarm features (age >50, blood, weight loss, anemia, family history).

Management

• Diet: Low-FODMAP trial (dietitian-guided).
• Loperamide for breakthrough; bile acid binders if BAM confirmed.
• Treat underlying condition (thyroid, celiac, IBD).
• Probiotics (specific strains: LGG, S. boulardii) modest benefit.
• Hydration + electrolytes (ORS).