101 - Diarrhoea

Question 0

Name 5 cell types seen in the GI tract.

Answer 0

Goblet cells - mucin -> mucous
Absorptive cells - especially on microvilli
Crypt cells
Panath cells
M cells - on payers patches in duodenum

Question 1

Name the two ways the GI tract acts as a barrier

Answer 1

The un stirred layer - mucus and bicarbonate

The apical membrane - lipid bilayer

Question 2

How does the shape of villi change in the GI tract?

Answer 2

Duodenum - long finger like
Jejunum - thicker
Ileum - leaf shaped
Large intestine - flatter.

Question 3

Where does most absorption take place?

Answer 3

Jejunum - 95% macronutrients absorbed

Question 4

How much is secreted into the GI tract? From where?

Answer 4

7l, saliva, bile, gastric and pancreatic juices

Question 5

What is plasma osmolarity?

Answer 5

290 mOsm/kg

Concentration of small molecules and ions in the lumen must be in equilibrium with this for correct stool consistency

Question 6

What role does intestinal flora play in digestion?

Answer 6

Ferment faecal material
Suppress overgrowth of pathogens
Alter pH
Affects hydration

Question 7

What is the clinical definition of diarrhoea?

Answer 7

3 or more loose or watery stoles in 24 hours. Acute is under 14 days, chronic over 14 days.

Dysentery - bloody and mucous stools and pain.

Question 8

Describe osmotic diarrhoea

Answer 8

Usually small intestine

When there is malabsorption/incomplete digestion causing larger, unmeasured osmoles to be in the lumen, which prevents reabsorption of adequate water. The osmoles alter the osmotic potential, so to maintain osmotic equilibrium water moves in and doesn’t get absorbed.

Question 9

What causes osmotic diarrhoea?

Answer 9

Rapid gut transit
Malabsorption
Osmotic laxative
Lactose intolerance

Question 10

Describe secretory diarrhoea

Answer 10

Usually in the large intestine
When large quantities of water are secreted into the lumen, and the body is overwhelmed and can’t reabsorption enough.
The electrolyte balance maybe disrupted, with excess NA+, K+, Cl- is left in the lumen, changing the osmotic potential

Question 11

What can cause secretory diarrhoea?

Answer 11

Cholera, infections, rotavirus, ETEC

Question 12

How can you distinguish between osmotic and secretory diarrhoea?

Answer 12

Stop eating - osmotic d will stop
If volume is very increased - secretory
Large ion gap (like normal) - osmotic diarrhoea

Question 13

What viruses cause diarrhoea?

Answer 13

Rotavirus -worldwide, infants, leading cause, winter, severe

Norovirus - contagious, 2nd most common, in industrialised countries, occurs in outbreaks

Astrovirus- sporadic diarrhoea. In winter. In outbreaks.

Enteric adenovirus -children, all year

Question 14

What parasites cause diarrhoea?

Answer 14

Giardiasis- osmotic diarrhoea. Contaminated water. Worldwide. Cysts excreted for months.

Cryptosporidium - worldwide. Animals, zoos, travellers.

Question 15

Name 7 bacterial causes of diarrhoea, and a key feature of each.

Answer 15

Salmonella - children. Animal food products

C diff- outbreaks. Recent antibiotics? Recent hosp admission? Over 65? Use PPI’s?

Cholera - secretory diarrhoea. Endemic. Poor sanitation and water suppy.

Shingellosis - severe dysentery in children and travellers. Poor sanitation. History of infection.

E-coli : ETEC - travellers and high deaths in children
EHEC - most common in USA, outbreaks

Campylobacter - birds and animals. 2nd most common travellers diarrhoea

Typhoid - S/SE Asia, Africa, E Europe. Enteric fever.

Question 16

How do you treat diarrhoea?

Answer 16

Replace fluid loss
Address cause
Stop diarrhoea

Question 17

How can you replace fluid loss?

Answer 17

ORA - dioralute. Water and NaCl and glucose. Works on corransporter of Na and glucose which changes osmotic potential so water dragged into body.

IV rehydration if severe

Question 18

What type of drug is loperamide?

Answer 18

GI opioid receptor agonist

• decreased bowel motility and increased tone of anal sphincter