Acute Diarrhoea ✅ Flashcards
What is the role of the gut?
- Maintain fluid homeostasis
- Allow absorption of dietary nutrients
How does the gut maintain fluid homeostasis?
Through absorption or secretion
What is the importance of allowing absorption of dietary nutrients?
Allow growth, repair, and maintain normal functions of the body
What happens when fluid homeostasis is not maintained by the gut?
Diarrhoea results
What is the result of the gut always absorbing nutrients to its maximal ability?
If calorie intake exceeds energy expenditure, obesity results
What is diarrhoea defined as?
The rapid transit of gastric contents through the bowel
How often do children open their bowels?
Frequency variable in childhood, but median is 1 bowel movement per day
What is considered to be diarrhoea in terms of bowel movements?
3 or more loose watery stools per day
What can protracted diarrhoea lead to?
Severe malnutrition
What can severe malnutrition caused by protracted diarrhoea lead to?
Prolonged impairment of physical and intellectual development
When in particular does malnutrition caused by diarrhoea have the potential to cause impairment of development?
When it occurs at a vulnerable period of brain development
At what age are episodes of acute diarrhoea most common?
In the first year of life
What is the problem with acute diarrhoea being most common in the first year of life?
- Brain development is incomplete
- Wide variety of intestinal transport mechanisms which are concerned with absorption and secretion of fluid are poorly developed
What can diarrhoea be categorised as?
- Osmotic
- Secretory
What is the problem in osmotic diarrhoea?
Excess osmotically active particles in the gut lumen
Why does excess osmotically active particles in the gut lumen lead to diarrhoea?
More fluid passively moves into the bowel lumen down the osmotic gradient, which may exceed the absorptive capacity of the gut and lead to diarrhoea
What happens in osmotic diarrhoea if the child is not fed?
The diarrhoea stops
What are the causes of osmotic diarrhoea?
- Ingestion of solutes which cannot be absorbed
- Malabsorption of specific solutes
- Damage to absorptive area of mucosa, resulting in less fluid absorption
- Motility disorders
Give an example of a solute that cannot be absorbed
Osmotic laxatives such as lactulose
Give 2 examples of causes of malabsorption of specific solutes
- Disaccharide deficiency
- Glucose-galactose malabsorption
Give 4 causes of damage to the absorptive area of the mucosa
- Gastroenteritis
- CMPA
- Coeliac disease
- Crohn’s disease
Give 3 examples of motility disorders
- Gastroschisis
- IBS
- Hyperthyroidism
Why can motility disorders lead to osmotic diarrhoea?
Can result in reduced contact with bowel lumen, therefore higher concentration of solutes within the lumen
What is the problem in secretory diarrhoea?
Bowel mucosa secretes excessive amounts of fluid
What are the causes of secretory diarrhoea?
- Activation of specific pathway by a toxin
- Inherent abnormalities in the enterocytes
Give an example of a toxin causing secretory diarrhoea
Cholera toxin
Give an example of an inherent abnormality causing secretory diarrhoea
Congenital microvillous atrophy
Are absorptive mechanisms present in secretory diarrhoea?
They are often still present, but overwhelmed
Does secretory diarrhoea stop if feeds are withheld?
No
Can osmotic and secretory diarrhoea occur together?
Yes
Can osmotic and secretory diarrhoea occur in acute and chronic disease?
Yes
What is the most common cause of acute diarrhoea?
Infective
Why might diarrhoea be a beneficial physiological response in the case of infectious diarrhoea?
Expels harmful bacteria and toxins from the body
What are the mechanisms behind infections causing diarrhoea?
- Damage to the mucosa
- Toxins produced by the infective organism
Give an example of a pathogen that causes gastroenteritis by damaging the mucosa
Rotavirus
Give an example of a pathogen that causes gastroenteritis by producing toxins
Cholera
What type of pathogen most commonly causes infectious diarrhoea?
Viruses
What is the most common virus causing infectious diarrhoea?
Rotavirus
At what time of year does viral gastroenteritis occur?
All year round, with peaks in winter and spring
Why are there peaks of viral gastroenteritis in winter and spring?
Due to rotavirus
When was the rotavirus vaccine introduced?
July 2013
Other than rotavirus, give 3 viruses causing diarrhoea
- Norwalk virus
- Norovirus
- Calcivirus
What is the most common bacterial cause of infectious diarrhoea?
Campylobacter
Other than campylobacter, give 5 bacterial causes of diarrhoea
- Salmonella
- Escherichia coli
- Shigella
- Yersinia enterocolitica
- Clostridium difficile
Give 2 parasites causing infectious diarrhoea
- Cryptosporidium
- Giardia lamblia
By what route are most enteric viruses transmitted?
Faeco-oral route
How can noroviruses spread?
- Contaminated food and water
- Via droplet spread from vomitus
What cells do viruses infect to cause diarrhoea?
Mature enterocytes of the small intestine
What happens when viruses infect mature enterocytes of the small intestine?
Cause cell destruction and villous atrophy
What does rotavirus cause when it infects the enterocytes of the small intestine?
Opening of calcium channels
What does the opening of calcium channels in rotavirus infection lead to?
Efflux of sodium and water into the intestinal lumen
When do fluid losses decrease in viral gastroenteritis?
Between days 2-5
When is villous structure restored in viral gastroenteritis?
Day 6-10
What does bacterial enterocolitis result from?
Mucosal invasion by bacteria and/or production of cytotoxins
What can haemolytic-uraemic syndrome occur following?
Infection with bacteria producing Shiga-like toxin, also known as verotoxin
What pathogen has haemolytic-uraemic syndrome traditionally been closely linked to?
E. Coli 0157:H7 strains
What are the most important complications of viral gastroenteritis?
- Dehydration
- Electrolyte abnormalities
What is the focus of management in gastroenteritis?
Largely supportive, with management of dehydration and electrolyte abnormalities
What is used to manage dehydration and electrolyte abnormalities in gastroenteritis?
Oral rehydration solution
What does ORS contain?
Sodium and glucose in specific proportions
Why is ORS effective in diarrhoeal illness?
The sodium-glucose transporter continues to work effectively even in the presence of inflammation (whereas chloride channels continue to cause secretion), so when sodium and glucose is given in the correct proportions, the absorption of sodium is increased with a consequent increase in passive water absorption
Does ORS stop the diarrhoea?
No
If ORS doesn’t stop the diarrhoea, why is it helpful?
The absorption of water and solutes will exceed the secretion, and will ensure the child remains hydrated until the infective organism is eradicated
What should ORS contain?
- 75mmol/L sodium
- 75mmol/L glucose
What is the total osmolality of ORS?
245mOsm/L
What has traditionally been used as rehydration solutions?
- Coke
- Apple juice
Why are coke and apple juice not suitable for use as rehydration solutions?
They have significantly lower content of sodium and very high osmolarity
What % of children with acute diarrhoea fail to respond with oral therapy?
Less than 5%
Should breastfed infants continue to be breastfed during an episode of acute diarrhoea?
Yes
Why should breastfed infants continue to be fed during an episode of acute diarrhoea?
It promotes faster recovery and rehydration
When may artificially fed infants return to normal feeding?
After a 6 hour period of oral rehydration solution, if they recover well
When are antibiotics used in gastroenteritis?
- Unusually long length of symptoms
- Immunocompromised hosts
Describe the use of probiotics in gastroenteritis?
Efficacy in treatment/recovery remains unclear, currently not recommended
What are the non-infective causes of acute diarrhoea?
- Inflammatory processes within the bowel
- Drug induced
How can inflammatory processes within the bowel lead to acute diarrhoea?
Causes a reduction in the absorptive surface of the bowel as the villi are damaged
Give 4 inflammatory processes that can cause acute diarrhoea
- Coeliac disease
- CMPA
- Acute appendicitis
- Intussusception
Give 2 drugs that can cause acute diarrhoea?
- Antibiotics
- Laxatives
How can antibiotics and laxatives cause diarrhoea?
May cause increased motility of the bowel, allowing less time for absorption
