Post-prandial diarrhoea
Diarrhoea triggered by eating: causes, investigations, and management
What is post-prandial diarrhoea?
Diarrhoea that occurs soon after meals. Often mislabelled as IBS without evaluation. Causes are often treatable.
Major causes
1. Bile acid diarrhoea
Common and under-diagnosed. Excess bile acids reach the colon, stimulating water secretion and rapid transit. Often after gallbladder removal. Management includes bile acid sequestrants (e.g. cholestyramine) and dietary fat moderation.
2. Dumping syndrome
After gastric/oesophageal surgery (including bariatric). Early dumping within 30 minutes (diarrhoea, cramping, palpitations, flushing, dizziness). Late dumping 1–3 hours (hypoglycaemia symptoms). Management: small frequent meals, reduced simple sugars.
3. Post-cholecystectomy diarrhoea
Continuous bile flow can overwhelm absorptive capacity; often bile acid diarrhoea.
4. Pancreatic exocrine insufficiency
Clues: post-meal diarrhoea, greasy stools, weight loss, vitamin deficiencies. Investigate with faecal elastase; manage with pancreatic enzyme replacement.
5. Rapid transit
Seen in functional disorders, post-infectious states, endocrine disorders.
6. Food-related triggers
Lactose intolerance, fructose malabsorption, FODMAP triggers — avoid over-restriction.
Assessment strategy
- Timing after meals
- Watery vs fatty stools
- Weight loss
- Surgical history (gallbladder, gastric, pancreas)
Useful investigations
- Coeliac serology
- Faecal elastase
- Bile acid testing (where available)
- Therapeutic trial of bile acid sequestrant
Key takeaway: Post-prandial diarrhoea is a symptom, not a diagnosis. Identifying the mechanism allows targeted treatment.