101 - Diarrhoea Flashcards
What is diarrhoea
Passage of 3 or more loose/liquid stools per day (or more frequent passage than is normal for the individual.
3 clinical types of diarrhoea - describe the diarrhoea
Acute watery diarrhoea
Acute bloody diarrhoea
Persistant diarrhoea
What is acute bloody diarrhoea called?
Dysentery
How long does persistent diarrhoea last?
> 14days
Red flag symptoms of clinical dehydration
Appears unwell/deteriorating
Altered responsiveness or irritability
Symptoms of clinical dehydration
Decreased urine output
Appears unwell/deteriorating
Altered responsiveness or irritability
Red flag signs of clinical shock
Altered responsiveness Sunken eyes Tachycardia Tachypnoea Reduced skin turgor
Signs of clinical shock
Decreased consciousness Pale, mottled skin Cold extremities Tachycardia Tachypnoea Weak peripheral pulses Prolongued capillary refill Hypotension
Red flag symptoms in diarrhoea - what do they indicate?
Increased risk of progression to shock
When do you treat as shock?
If one or more red flag signs is present
Clinical dehydration - % dehydration
5-7% dehydration
Clinical shock - % dehydration
~10% dehydration. Need to treat - likely fatal if not.
Can meningitis present with just diarrhoea and vomiting?
Yes
If patient has diarrhoea - always need to ask about what?
Vomitting
Skin turgor test - how long should the childs abdomen take to return to normal after pinching? What does a slow skin pinch indicate?
Normal = immediate
Slow = 1 sec
Very slow = 2 or more secs
Slow skin pinch indicates severe dehydration
What is osmotic diarrhoea
Diarrhoea due to too much water drawn into bowels through osmosis
What mechanisms can cause osmotic diarrhoea? (Mechanism and 3 causes)
Large amounts of hypertonic substances in lumen.
Can be due to:
Ingested hypertonic substances
General malnutrition
Defects in absorption of hypertonic substances
What about diarrhoea would make you think osmotic? (3)
Moderately increased stool volume,
Diarrhoea stops when fasting
Normal-increased stool osmolarity
What is secretory diarrhoea?
Diarrhoea due to active secretion of fluid and electrolytes from gut wall.
May be due to irritants or hormones.
Most common cause of secretory diarrhoea?
Cholera
What about diarrhoea would make you think secretory? (3)
Very large increase in stool volume, diarrhoea continues when fasting, normal stool osmolarity
What mechanisms cause secretory diarrhoea?
Toxin mediated
Symptoms of inflammatory diarrhoea
Pain, bloody, mucoid stools, weight loss
Main causes of inflammatory diarrhoea (4)
Infections, auto-immune disease (IBD), food sensitivity (Coeliac) & others (radiation exposure)
Consequences of diarrhoea (5)
Can be fatal
Dehydration
Loss of electrolytes - disordered physiology
Can cause malnutrition if prolonged
Inflammation - can cause mucosal damage, gastrointestinal haemorrhage, perforation and sepsis.
Rotavirus facts
Vaccinated against
Leading case of gastroenteritis worldwide
Causes up to 40% cases of severe diarrhoea in infants
Shed in high titres in stools for up to 21 days post onset of symptoms
Norovirus facts
Most commonly in winter in closed communities. Highly contagious.
Campylobacter facts
Birds/animals are infection reservoirs.
Faeces is source of infection.
Transmission by contaminated water, food and milk as well as person to person. Second most common cause of travellers diarrhoea.
Salmonella facts
Mainly transmitted by contaminated animal foods. Mostly affects young children. Shedding can persist and antibiotics can prolong shedding. 1% become chronic carriers and continue to shred for >1year
E. Coli facts
Transmitted by direct contact or contaminated food. 5 strains - 2 key.
EHEC - Enterohaemorrhagic - Most common cause diarrhoea in USA.
ETEC - Major cause travellers diarrhoea in countries with poor sanitation.
Cholera facts
Endemic to most countries with poor sanitation. Outbreaks esp after contamination of water supplies.
C. diff facts
Commensal gut bacteria. Diarrhoea associated with toxin secretion. Can be life threatening in elderly. Majority of healthcare acquired diarrhoea.
3 major risk factors for C.diff
Recurrent antibiotic use, admission to hospital, aged over 65.
Giardiasis facts
Most common parasitic diarrhoea. Human and animal reservoirs. Transmission through direct contact or ingesting cysts from faecally contaminated water.
What is chyme?
Semi-fluid mass of partially digested food that is expelled by the stomach into the duodenum. Acidic.
Action of the duodenum
Chyme neutralised by bile and bicarbonate and further digested by enzymes from pancreas, liver and small intestine.
Role of the small intestine
Site of most nutrient absorption and removal of largest volume of water
Role of the large intestine
Remove as much remaining water as possible and absorb electrolytes, complex carbohydrates and fibre.
Treatment of diarrhoea - therapeutic objective?
Replace lost fluid
Address underlying case
Reduce passage of stools
How do oral rehydration salts work?
Contain NaCl and glucose. Replace lost ions to allow the water to be absorbed by osmosis
Water lost in mild dehydration
1-2L
Water lost in moderate dehydration
2-4.5L
Water lost in severe dehydration
> 4.5L
When are oral rehydration salts not suitable as treatment for diarrhoea?
Severely dehydrated
Tachycardic.
Patients at risk of serious consequences from dehydration
May need IV fluids instead
How fast does dehydration need to be corrected by for oral rehydration to be appropriate
Within 4hrs. If will take longer then IV fluids needed.
Antibiotics to treat E.Coli 0157
Contraindicated
Antibiotics for cholera
Doxycyclin
Antibiotics for Giardia
Metronidazole
Antibiotics for C.diff
Metronidazole or vancomycin
How does reducing passage of stools help diarrhoea?
Doesn’t help address cause or correct dehydration. Convenience of patient.
Side effects for reduction of stools
Toxins can be retained. Can cause problems if gut is susceptible to damage from holding on to waste.
Mechanism of action for loperamide (Imodium)
Opioid receptor agonist. Acts on surface receptors in bowel to decrease motility by decreased peristalsis and increases sphincter tone. Increases transit time so more water is absorbed.
Drug trial into efficacy of loperamide showed:
When given as recommended - showed reduction in stool number of ~50% for 1st two days.
When should racecadotril be used?
Most patients - no additional benefit and is very expensive. Reduces hyper secretion without affecting transit time.. Reduction in constipation as a side effect compared to loperamide.
Common name for Loperamide
Imodium
4 stages for drug disposition
Absorption
Distribution
Metabolism
Excretion
2 ways for drugs to move around body
Bulk flow - in blood, lymph, CSF.
Diffusion - short distances only.
Drug diffusion - what affects ability to cross hydrophobic diffusion barriers
Lipid solubility
What mainly affects rate of diffusion of a substance
Molecular size
How can small molecules cross cell membranes (4)
Diffusing through liquid
Combination with solute carrier
Pinocytosis
Diffusing through membrane pores
What does mucosal resistance determine?
How effectively liquid can cross the membrane and be absorbed.
How much water should faeces contain
~100mL. More = Diarrhoea, Less = constipation.
Why do gastric secretions get removed in the large intestine
Role of secretions complete.
How does most water reabsorption take place in the bowels and where does it mainly occur.
Via Na+ driven transport across a sodium-potassium pump, active transport. Creates osmotic gradient so water moves out of the lumen and across the membrane.
Mainly occurs in small intestine.
How is surface area of small intestine increased and why?
Increased by villi coated in microvilli - increases x600 compared to smooth tube of same diameter. Increased surface area allows increased nutrient absorption.
Where are there more villi in the small intestine.
At the start as more nutrients absorbed at the start of the small intestine than the end.
What does the duodenum do?
Small part of small intestine. Site of neutralisation of chyme.
Role of jejunum
Absorbs >95% macronutrients.
Role of Ileum
Absorbs nutrients not absorbed in jejunum, fibre, bile acids, Vit B12, water & electrolytes.
Role of goblet cells in small intestine
Mucus secretion - protective role
Role of crypt cells in small intestine
Site of new cell generation
Role of paneth cells in small intestine
Contain eosinophilic secretory granules. Probably involved in intestinal barrier function.
Role of M cells in small intestine.
Form peyers patches. Probably has a role in helping intestine respond to toxins.
Role of large intestine
Carbohydrate absorption and digestion
How is large intestine different to small intestine?
Less villi - fine tuning of ions not bulk water reabsorption.
What is transit time?
Time for digestion. What is normal for patient? 3x day - 1 in 3 days is normal range.
High volume diarrhoea indicates problem with
Small intestine - lack of bulk water reabsorption.
Small volume diarrhoea indicates problem with
Large bowel - most water reabsorbed by small bowel
Electrolyte absorption in osmotic diarrhoea is
Normal. Carbohydrate comprises most of osmotic gap.
Electrolyte absorption in secretory diarrhoea is
Reduced. Less able to reabsorb electrolytes.
Describe steatorrhoea
Pale, offensive, floating stool. Too much fat present.
Investigations for diarrhoea
Stool sample,
Sigmoidoscopy and rectal biopsy in persistent cases
Treatment of diarrhoea
Treat dehydration - fluids/ORT
Treat cause - antibiotics may be needed.
Stop diarrhoea - Imodium.
Are antibiotics generally given for diarrhoea?
Not in simple gastroenteritis. Usually resolves quickly without antibiotics and in the UK diarrhoea generally has a viral cause.
Young toddler recently started playschool
Rotavirus
Elderly person recently treated with penicillin for chest infection
C.Diff
Recently been travelling to Europe/Latin America
Travellers diarrhoea - E.Coli
Rice water diarrhoea
Cholera
Fatty stools
Giardia lambilia (Parasite)
Eaten rice
Bacillus Cereus
Eaten Chicken
Campylobacter (lasts 2-5 days) or Salmonella (Lasts 48hrs)
What is Coeliac disease
Autoimmune disease - gluten intolerance.
Mechanism of coeliac disease
Inflammatory response to gluten leads to villous atrophy
Signs and symptoms of coeliac disease
Steatorhoea, Bloating, fat soluble vitamin malabsorption, Anaemia
Treatment of coeliac disease
Gluten free diet
Dietary supplements
Rule out cancer/ulcerative jejunitis if no improvement
What is the immediate priority for treating a sick child?
Assess to identify any compromised vital signs and stabilise condition (ABCDE)
Impact of severe acute malnutrition on clinical signs of shock/dehydration.
Makes the clinical signs/symptoms unreliable.
Impact of parental fluids in severe acute malnutrition
Can cause severe dehydration
