Diarrhoea

Question 1

What is the role of the CFTR (cystic fibrosis transmembrane conductance regulator)

Answer 1

Secrets Cl- , in normal conditions, the CFTR is closed or not present

Question 2

What activates the CFTR channels to result in secretion?

Answer 2

Bacterial enterotoxins
Hormones and neurotransmitters
Immune cells products
Some laxatives

Question 3

Which second messengers are activated that result in the activation of CFTR

Answer 3

cAMP
cGMP
Ca2+

Question 4

What are the causes of diarrhoea?

Answer 4

E.coli
Impaired absorption of NaCl
Non-absorbable, or poorly absorbable, solutes in intestinal lumen
Hypermotility

Question 5

How does E. coli cause diarrhoea?

Answer 5

Cholera toxin enters enterocyte
Enzymatically inhibits GTPase activity of GS subunit
Increases activity of Adenylate Cyclades
Increased conc of cAMP
stimulated CFTR
Cl-, Na+ and water hypsersecreted

Question 6

How does impaired absorption of NaCl cause diarrhoea?

Answer 6

There is infection, resulting in inflammation and destruction of the intestinal absorptive epithelium

Question 7

What is poorly soluble in intestinal lumen?

Answer 7

Lactate, lactose intolerance, resulting in diarrhoea

Question 8

Why does hypermotility result in diarrhoea?

Answer 8

Excess peristalsis of the GI reduces the reabsorption of solutes and water

Question 9

What is the process of rehydration therapy? Na+/glucose co transport

Answer 9

2Na+ bind
Affinity for glucose increases glucose binds
Na+ and glucose translocate from extracellular to intracellular
2Na+ dissociate, affinity for glucose fallen
Glucose dissociates
Cycle is repeated

Question 10

How do you rehydrate at home

Answer 10

6 teaspoons of glucose
0.5 teaspoons glucose
Dissolved in 1L water

Question 11

What is mechanism of action for anti motility agents

Answer 11

Inhibition of enteric neurones
Decreased peristalsis, increases segmentation
Increased fluid absorption
Constriction of pyloric, ileocecal and anal sphincters

Question 12

Give example of anti motility agents

Answer 12

Codeine
Diphenoxylate
Loperamide

Question 13

What is lactose intolerance?

Answer 13

Inability to adequately digest lactose, lactose insufficiency

Question 14

What are causes of lactose intolerance?

Answer 14

Primary lactase deficiency (primary hypolactasia) - due to lack of the lactase persistence (LP) allele
Secondary lactase deficiency - caused by damage to/infection of the proximal small intestine
Congenital lactase deficiency - rare autosomal recessive disease - no ability to digest lactose from birth

Question 15

What are the symptoms of lactose intolerance

Answer 15

Bloating
Abdominal pain
Flatulence
Diarrhoea

Question 16

How is lactose intolerance diagnosed?

Answer 16

Symptoms
Hydrogen breath test
Lactose/milk tolerance test

Question 17

What is the treatment for lactose intolerance?

Answer 17

Reduction/elimination of consumption of milk products
Use of milk products treated with lactase
Use of milk lactose free

Question 18

What are the causes of constipation

Answer 18

Neurogenic disorders
Abdominal muscle weakness
Diet poor of fibres
Sedentary lifestyle 
Constant suppression of the urge to empty 
Antidepressant drugs
Opiates
Ageing

Question 19

Give examples of purgatives for constipation

Answer 19

Bulk laxatives - polysaccharide polymers not digestible
Osmotic laxatives - poorly absorbed solutes
Faecal softeners - enema
Stimulant laxative - drugs that directly increase peristalsis
Anti-emetics = increase GI motility without purgation and gastric emptying