302 Pathogenesis of diarrhoea and inflammatory bowel disease Flashcards
What is the definition of diarrhoea?
Increase in volume and frequency of stool
What is inflammatory diarrhoea?
Caused by inflammation / ulceration / necrosis / infection / chemical damage
(A disruption to mucosal integrity)
Mucous, serum, blood are lost
Inflammatory mediators cause secretion
Thick abnormal mucosa doesn’t absorb well
Small bowel – malabsorption of nutrients
Large bowel – poor reabsorption of water
Diarrhoea all the time, but worse when you eat
What are the 2 types of inflammatory bowel disease?
Crohn’s disease
Ulcerative colitis
What is Ulcerative colitis?
Inflammation of the colon only
Always starts distally (in the rectum) and is continuous
Mucosa/submucosal only
What is Crohn’s disease?
Any part of the GI tract
Characterised by “skip lesions” = normal bowel between affected sections
Full thickness of bowel wall
Perforating/fistulating
Stricturing
Peri-anal disease
What are the main symptoms on UC?
Bloody diarrhoea
What are the main symptoms of Crohn’s disease?
Bloody diarrhoea is less common
Non-bloody diarrhoea
Abdo pain
Weight loss
Pyrexia
Mouth ulcers
Perianal disease
What is the histopathology of UC?
Chronic inflammatory cells
Mucosal only
Crypt abscesses
Crypt distortion
Goblet cell depletion
What is the histopathology of Crohn’s disease?
Chronic inflammatory cells
Full wall thickness
Lymphoid hyperplasia
Granulomata
What are the causes of inflammatory bowel disease?
Familial/Complex genetic
Luminal antigens:
Diet
Bacteria
Mucosal Barrier Dysfunction
Smoking:
Makes Crohn’s worse
Quitting may make UC worse
What is the age of diagnosis of inflammatory bowel disease?
Most common 20-30 years for both
UC is commonly diagnosed later in life as well but not Crohn’s
What is osmotic diarrhoea?
Poorly absorbed osmotic solutes in lumen
Inhibit salt and water reabsorption
Diarrhoea completely stops if you don’t eat
Malabsorption may be specific (e.g. lactose, bile salts)
What is coeliac disease?
Dietary gluten (wheat and barley damages small bowel mucosa
Most damage is proximal (jejunal) tails off in distal small bowel (ileum)
Antibodies involved but how?
Eg. TTG, anti-endomysial, anti-gliadin
All damages resolves if gluten is excluded from diet
Who gets coeliac disease?
Any age
Women > men
1 in 1000 Europeans (1 in 300 in Ireland)
1 in 10 with affected first degree family member
HLA associations
Trigger is unknown
How is coeliac disease diagnosed?
Screen with serology
Gold standard: biopsy
What is secretory diarrhoea?
Occurs when your body secretes electrolytes into your intestine
Caused by bacterial endotoxins and rotavirus
Not affected by fasting
What is a Rotavirus?
Causes acute enteritis
Faeco-oral transmission
Nearly every child has had it by age 5
37% of childhood deaths from Diarrhoea
In UK vaccinated as babies
How does Rotavirus cause diarrhoea?
NSP4 toxin :
induces chloride secretion
Disrupts transporter-mediated water reabsorption
Affects the enteric nervous system to promote secretory reflexes
What types of diarrhoea does coeliac disease give you?
Osmotic
What type of diraahoea is salmonella?
Inflammatory
What type of diarrhoea is lactose intolerance?
Osmotic
