lecture 12 - case 2 intro

Question 1

What are the 4 mechanisms of diarrhoea?

Answer 1

1. Osmotic
2. Secretory
3. Inflammatory
4. Motility
   (MISO?)

Question 2

What is diarrhoea?

Answer 2

Increase in frequency and/or decreased consistency of stool

Question 3

What causes cramps/pains with diarrhoea?

Answer 3

Increased volume of water in the lumen leads to increased stretch and therefore increased motility causing cramping

Question 4

What is osmotic diarrhoea?

Answer 4

Diarrhoea caused by failure to reabsorb secretions from higher in the GI tract

Question 5

What is secretory diarrhoea?

Answer 5

Increased secretion of water and electrolytes into the lumen due to increased chloride secretion

Question 6

What is inflammatory diarrhoea?

Answer 6

Increased liquid in the bowels due to leaking from inflamed, leaky mucosa

Question 7

What is motility-induce diarrhoea?

Answer 7

Dramatically increased gut motility can prevent the absorption of water in the colon, resulting in more frequent, runny stools

Question 8

What bacteria most commonly causes secretory diarrhoea?

Answer 8

Cholera - Vibrio cholerae

Question 9

What is the mechanism by which cholera causes secretory diarrhoea?

Answer 9

Cholera toxin binds to intestinal secretory cells and activates Cl channels, resulting is secretion of Cl into the gut lumen. To maintain electrochemical gradient, cations (Na+) follows bringing with it H2O down the osmotic gradient. This results in an increased volume of water and salt in the lumen = diarrhoea

Question 10

What is the osmolarity of the fluid lost in secretory diarrhoea (e.g. cholera)?

Answer 10

isosmotic (na and h2o are pumped into the lumen)

Question 11

Why is K+ and HCO3 secretion into the lumen increased with secretory diarrhoea?

Answer 11

Increased concentration of Cl, Na and H2O in the lumen drives exchange, causing depletion of K+ and HCO3

Question 12

What are the effects of lost K+ and HCO3- in secretory diarrhoea?

Answer 12

Hypokalaemia (can lead to arrhythmia), acidosis

Question 13

What is the most important non-pharmacological treatment for secretory diarrrhoea, e.g. cholera?

Answer 13

Fluid replacement - IV saline or oral rehydration with electrolytes

Question 14

Which fluids should be given IV in patients with secretory diarrhoea?

Answer 14

0.9% saline - because loss is isosmotic

Question 15

Which symptom is most suggestive of secretory diarrhoea as opposed to the other types?

Answer 15

Diarrhoea continues during fasting, because secretion continues to produce fluid even though no food is being digested.