Diarrhoea Flashcards
What is diarrhoea defined as?
Passage of 3 or more loose or watery stools in 24 hours.
How does the excess fluid in the GI lumen come about?
Loss of absorptive capacity of the small intestine is usually compensated for in mild diarrhoea by increased absorption in the colon.
If this is also interrupted, then the colon becomes overwhelmed with fluid.
Fluid can also enter the GI lumen if the tight junctions between cells are damaged or if cells are lost.
How can potassium ions be lost in diarrhoea?
K ion loss can occur with complete cell loss, but also without cell loss, in cholera. In cholera stool has high K and bicarb concentrations.
What can bicarbonate loss lead to?
Acidosis, since H ions enter the cells in exchange for K, meaning intra and extracellular K is depleted, causing hypokalaemia.
Why does sustained diarrhoeal disease deplete ECF volume?
Sodium ion absorption is enhanced as much as possible after dehydration, which are exchanged for K and H ions.
What is osmotic diarrhoea?
Increased number of osmotic particles in the lumen causes water to flow into the lumen.
More sugars, amino acids, and other absorbed nutrients in the lumen decreases intestinal absorption and increases water and sodium in the lumen.
What can cause osmotic diarrhoea?
Eating loads of sugar
Coeliac disease
Pancreatic insufficiency
How do you stop osmotic diarrhoea?
Fasting
What is secretory diarrhoea?
Increased intestinal secretion, usually due to bacterial enterotoxins
How do bacterial enterotoxins cause secretory diarrhoea?
Toxins stimulate anion release (Cl) into the lumen, and Na follows to maintain the charge balance which causes water to enter the lumen too.
E.coli makes a heat stable enterotoxin that prevents absorption from villi
Cholera makes a heat labile toxin which acts on secretory cells to increase Cl secretion, causing Na and water to enter lumen. It also loosens tight junctions.
C.diff makes enterotoxins that cause epithelial cells to fall off mucosa which leaves spaces for fluid to flow through.
What is inflammatory diarrhoea?
Damage to intestinal mucus cells causes exudation of mucus, blood and protein from sites of active inflammation into the bowel lumen.
What can cause inflammatory diarrhoea?
Chrons disease
Ulcerative colitis
What can cause motility diarrhoea?
Diabetes
Neurotoxins
What can cause secretory diarrhoea?
Infectives and laxatives
What are the typical symptoms of SI diarrhoea?
Large volume, infrequent and cramps.
SI goes into overdrive and secretes lots of fluid and enzymes
