302 Pathogenesis of diarrhoea and inflammatory bowel disease

Question 1

What is the definition of diarrhoea?

Answer 1

Increase in volume and frequency of stool

Question 2

What is inflammatory diarrhoea?

Answer 2

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

Question 3

What are the 2 types of inflammatory bowel disease?

Answer 3

Crohn’s disease
Ulcerative colitis

Question 4

What is Ulcerative colitis?

Answer 4

Inflammation of the colon only

Always starts distally (in the rectum) and is continuous
Mucosa/submucosal only

Question 5

What is Crohn’s disease?

Answer 5

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

Question 6

What are the main symptoms on UC?

Answer 6

Bloody diarrhoea

Question 7

What are the main symptoms of Crohn’s disease?

Answer 7

Bloody diarrhoea is less common

Non-bloody diarrhoea
Abdo pain
Weight loss
Pyrexia
Mouth ulcers
Perianal disease

Question 8

What is the histopathology of UC?

Answer 8

Chronic inflammatory cells
Mucosal only
Crypt abscesses
Crypt distortion
Goblet cell depletion

Question 9

What is the histopathology of Crohn’s disease?

Answer 9

Chronic inflammatory cells
Full wall thickness
Lymphoid hyperplasia
Granulomata

Question 10

What are the causes of inflammatory bowel disease?

Answer 10

Familial/Complex genetic

Luminal antigens:
Diet
Bacteria

Mucosal Barrier Dysfunction

Smoking:
Makes Crohn’s worse
Quitting may make UC worse

Question 11

What is the age of diagnosis of inflammatory bowel disease?

Answer 11

Most common 20-30 years for both

UC is commonly diagnosed later in life as well but not Crohn’s

Question 12

What is osmotic diarrhoea?

Answer 12

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)

Question 13

What is coeliac disease?

Answer 13

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

Question 14

Who gets coeliac disease?

Answer 14

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

Question 15

How is coeliac disease diagnosed?

Answer 15

Screen with serology
Gold standard: biopsy

Question 16

What is secretory diarrhoea?

Answer 16

Occurs when your body secretes electrolytes into your intestine

Caused by bacterial endotoxins and rotavirus

Not affected by fasting

Question 17

What is a Rotavirus?

Answer 17

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

Question 18

How does Rotavirus cause diarrhoea?

Answer 18

NSP4 toxin :
induces chloride secretion
Disrupts transporter-mediated water reabsorption
Affects the enteric nervous system to promote secretory reflexes

Question 19

What types of diarrhoea does coeliac disease give you?

Answer 19

Osmotic

Question 20

What type of diraahoea is salmonella?

Answer 20

Inflammatory

Question 21

What type of diarrhoea is lactose intolerance?

Answer 21

Osmotic