Pathophysiology of Diarrhoea

The World Health Organization’s definition of diarrhoea is the passage of three or more loose or liquid stools per day, or more frequently than is normal for the individual.

Diarrhoeal disease is the second leading cause of death in children under five years old after pneumonia. Three clinical types of diarrhoea include acute watery diarrhoea e.g. cholera; acute bloody diarrhoea (dysentery) and persistent diarrhoea for > 14 days.

Death from diarrhoea is mainly due to dehydration and loss of essential electrolytes (sodium, chloride, potassium and bicarbonate) and it is more fatal in young children, malnourished and immunocompromised patients.

The main causes of diarrhoea are infections such bacterial (mainly Escherichia Coli), viral (mainly rotavirus) and parasitic infections and infestation; malnutrition and contaminated water or food.

Treatment of diarrhoea includes rehydration; zinc supplements (which reduce the duration of a diarrhoeal episode); nutrient-rich foods, and antimicrobials in case of infections.

Types of diarrhoea:

1. Secretory Diarrhoea

Occurs when there is an increase in the active secretion of ions or when there is an inhibition of absorption of the same.

Examples include: diarrhoea due to cholera toxin which chloride ions (and others anions) are secreted actively and sodium and water are carried with it to maintain electrical potential and tonicity.

2. Osmotic Diarrhoea

Results from water that is substantially drawn into the intestine osmotically. Causes of osmotic diarrhoea include maldigestion, osmotic laxatives, lactose intolerance etc.

3. Exudative Diarrhoea

Characterized by blood and pus in the stool as observed in inflammatory bowel diseases (e.g. Crohn’s disease, ulcerative colitis, E. coli and food poisoning).

4. Motility-related Diarrhoea

This results from hypermobility e.g. vagotomy and diabetic neuropathy.

5. Inflammatory Diarrhoea

Results from damage to the mucosal lining or brush border. (e.g. pathogenic infections, autoimmune diseases that include inflammatory bowel disease)

6. Dysenteric Diarrhoea

Characterized by blood in the stool that signifies GIT infections by Shigella, Entamoebahistolytica, and Salmonella among others.

Management of diarrhoea includes prevention and restoration of fluid and electrolyte loss (as the first objective of management of diarrhoea), anti-biotics and anti-diarrhoeal.

Anti-diarrhoeal is classified into 2 groups:

a. Antimotility drugs e.g. codeine phosphate, loperamide and co-phenotrope.

b. Adsorbents and bulk-forming drugs e.g. light kaolin, attapulgite

Oral rehydration therapy: Constitutes the first line of treatment in acute diarrhoea, especially in infants, the frail and the elderly.

Antispasmodics: Used in the treatment of abdominal cramps associated with diarrhoea.

Attapulgite: A purified native hydrated aluminium magnesium silicate. Activated attapulgite has been heated to increase its absorptive activity.

Kaolin: Hydrated aluminium silicate with adsorbent properties.

Pectin: A purified carbohydrate obtained from the rind of citrus or apple pomace. It is an adsorbent as well as an absorbent.

Furazolidine: A synthetic nitrofuran antimicrobial. It has antibacterial, antifungal and antiprotozoal actions. It is active against E. coli, staphylococci, Salmonella, Shigella, Proteus, Aerobacter aerogenes, Vibrio cholera and Giardia lamblia.

Charcoal: Has adsorbent, defoliant, soothing properties. It reduces the volume of intestinal gas.

Cholestyramine: Can be used for the treatment of diarrhoea after an ileal disease or resection. It acts by binding to bile salts