Intestinal water and electrolyte transport and the mechanisms of diarrhoea
The daily intestinal fluid balance, the absorptive and secretory transporters of villus and crypt, how cholera and E. coli toxins, VIP, bile acids and osmotic loads cause diarrhoea, the stool osmotic gap worked through, why oral rehydration solution works, and why a high-output jejunostomy worsens with water.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- The gut handles about 9 L of fluid a day and passes 100 to 200 mL. A small fall in absorption or rise in secretion overwhelms the colon's reserve of about 4 to 5 L/day.
- Villus cells absorb; crypt cells secrete. Absorption is driven by sodium, secretion by chloride through CFTR. Water follows both passively.
- Diarrhoea is osmotic (unabsorbed solute, stops with fasting), secretory (transport switched to secretion, continues with fasting), inflammatory, or motility-related.
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Sources
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease (11th ed.)Elsevier (Feldman, Friedman, Brandt, 2021), 2021
- Guyton and Hall Textbook of Medical Physiology (14th ed.)Elsevier (Hall, Hall, 2021), 2021
- World Health Organization and UNICEF. Oral rehydration salts: production of the new ORS (WHO/FCH/CAH/06.1)World Health Organization, 2006
- Arasaradnam RP et al. Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition. Gut 2018;67(8):1380-99British Society of Gastroenterology, 2018
- Nightingale J, Woodward JM. Guidelines for management of patients with a short bowel. Gut 2006;55(Suppl 4):iv1-12British Society of Gastroenterology, 2006
- Last updated
- 14 November 2026
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