Diarrhoea
Definition
- > 3 loose/liquid stools/day or ^ frequency (WHO definition)
Pathogenesis
- Decrease in water absorption in small and large bowel
Mechanism
- Osmotic - increase osmotically active substances in gut. Malabsorption -
e.g. fat, bile acids/salts, lactose. Medications - osmotic laxatives
(lactulose, sorbitol)
- Secretory - active water secretion into gut e.g. cholera toxin, stool
softeners (Coloxyl)
- Motility related ^ - IBS, irritant laxatives (Senekot), v - bacterial
overgrowth>malabsorption
- Inflammatory - injury to gut epithelium (enterocyte) e.g. inflammatory
bowel disease, infectious colitis, dysentery
NB often multiple mechanisms occur in any one diseaseComplications
- Water loss (dehydration) > Shock > Acute Renal Failure
- Electrolyte loss
+/- complications related to the disease or other manifestations e.g. blood
loss/anaemia, malabsorption (see Lecture 2), hepato-biliary complications
from IBD.