101 - Diarrhoea Flashcards
Name 5 cell types seen in the GI tract.
Goblet cells - mucin -> mucous Absorptive cells - especially on microvilli Crypt cells Panath cells M cells - on payers patches in duodenum
Name the two ways the GI tract acts as a barrier
The un stirred layer - mucus and bicarbonate
The apical membrane - lipid bilayer
How does the shape of villi change in the GI tract?
Duodenum - long finger like
Jejunum - thicker
Ileum - leaf shaped
Large intestine - flatter.
Where does most absorption take place?
Jejunum - 95% macronutrients absorbed
How much is secreted into the GI tract? From where?
7l, saliva, bile, gastric and pancreatic juices
What is plasma osmolarity?
290 mOsm/kg
Concentration of small molecules and ions in the lumen must be in equilibrium with this for correct stool consistency
What role does intestinal flora play in digestion?
Ferment faecal material
Suppress overgrowth of pathogens
Alter pH
Affects hydration
What is the clinical definition of diarrhoea?
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.
Describe osmotic diarrhoea
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.
What causes osmotic diarrhoea?
Rapid gut transit
Malabsorption
Osmotic laxative
Lactose intolerance
Describe secretory diarrhoea
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
What can cause secretory diarrhoea?
Cholera, infections, rotavirus, ETEC
How can you distinguish between osmotic and secretory diarrhoea?
Stop eating - osmotic d will stop
If volume is very increased - secretory
Large ion gap (like normal) - osmotic diarrhoea
What viruses cause diarrhoea?
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
What parasites cause diarrhoea?
Giardiasis- osmotic diarrhoea. Contaminated water. Worldwide. Cysts excreted for months.
Cryptosporidium - worldwide. Animals, zoos, travellers.
Name 7 bacterial causes of diarrhoea, and a key feature of each.
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.
How do you treat diarrhoea?
Replace fluid loss
Address cause
Stop diarrhoea
How can you replace fluid loss?
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
What type of drug is loperamide?
GI opioid receptor agonist
- decreased bowel motility and increased tone of anal sphincter
