Diarrhoea Medical Model

Diarrhoea: malabsorption of water, water stools 

Short term/acute diarrhoea

Causes:

• virus e.g norovirus/rotavirus - rotavirus replicates within villous epithelium of small bowel, causes patchy epithelial cell destruction and villous shortening. Loss of these villous cells causes intestines to secrete water and electrolytes. Villous damage may also be associates with loss of disaccharie enzymes, especially lactose. Rotavirus probably spread from person to person
• norovirus - group of viruses that cause gastroenteritis which is infection of th egut. It causes vomiting and diarrhoea. Virus enters small intestine and multiplies 12-48 hours before symptoms show. Lining of small intestine has attachment for virus, attaches itself and releases genome. Genes shut down cells normal function and take controol of cell to make more viruses. 
• Bacteria e.g campylobacter, clostridium difficile, e.coli, salmonella, shigella - can all cause food poisoning
•  mucosal adhesion which is when bacteria that multiple within the small intestine must adhere to mucosa to avoid being swept away. It happens with e.coli. May cause changed in gut epithelium and reduce absorptive capacity or cause fluid secretion
• toxins that cause secretion - e.coli, salmonella, cause intestinal secretion by producing toxins after epithelial cell function, toxins reduce absorption of sodium by villi may increase secrtion of chloride in crypts result in net secretion of water and electrolytes
• mucosal invasion - shigella, cause bloody diarrhoea by destroying mucosal epithelial cells. Occurs in colon and distal part of ileum Microabcess form and superficial ulcers. Tissue damage and mucosal secretion of water and electrolytes 
• parasites - Giardia intestinalis parasite that causes giardiasis.

Long term/chronic diarrhoea : lasts longer than 3 weeks

Causes:

• irritable bowel syndrome - food moves through digestive system either too quickly or too slowly…