Pathogenesis CD/UC

Question 1

What is Crohn’s?

Answer 1

Chronic progressive patchy inflammation of the gut wall
- Causes transmural patchy inflammation anywhere in the GIT (from mouth to rectum)

Consists of flares and remissions
Fistulae and strictures can occur
Hyperplasia and luminal invasion
RLQ masses occur

Question 2

What causes Crohn’s?

Answer 2

Poor tolerance to bacteria in the gut
Autoimmune response
Genetic predisposition

Often multifactorial and idiopathic
Generally more debilitating than UC due to multiple surgeries being required

Question 3

What is dysbiosis?

Answer 3

Imbalance between the good and the bad bacteria

Question 4

What genetic factors are thought to be involved in Crohn’s?

Answer 4

Variation in

• CARD15 gene on chromosome 16
• Increased risk in caucasians

Question 5

What causes the immune response in IBD?

Answer 5

Inappropriate and ongoing activation of the mucosal immune system due to:
- Defective mucosal barrier and microbial clearance

Question 6

What is ulcerative colitis?

Answer 6

Chronic progressive generalised epithelial ulceration

• Inflammation limited to the colon in the GIT
• widespread mucosal inflammation (superficial)
• not commonly associated with fistulae and strictures

Acute condition can occur rapidly and become life threatening

Question 7

What are crohn’s and ulcerative colitis classified as?

Answer 7

Inflammatory bowel disease (IBD)

Question 8

What age group has the peak onset?

Answer 8

20 - 40 years old

but can occur in elderly/children

Question 9

What genetic factors are thought to be involved in UC?

Answer 9

Variations in:

• IL-10 gene (chromosome 1)
• ARP2C region (chromosome 2)
• Increased risk in south asians

Question 10

What environmental factors affect risk of Crohn’s?

Answer 10

Refrigerators
Western food preparation (not exposed to bacteria, thus when exposed triggers immune response)
Smoking
MAP 
Contraceptive pill
NSAIDs
Stress

Question 11

What is MAP?

Answer 11

Mycobacterium avium subspecies paratuberculosis

• Last resort treatment is intensive anti-MAP therapy (antibiotics)
• More evidence needed, but bacteria found in cows/sheep which survives pasteurisation in dairy products

Question 12

What environmental factors affect risk of UC?

Answer 12

Smoking cessation
Western food prep
NSAIDs
Stress
Pollution

Question 13

What are RLQ masses and what are they associated with?

Answer 13

Right lower quadrant abdominal masses

- Crohn’s disease

Question 14

Endoscopy image of Crohn’s

Answer 14

Mucosal inflammation

• Redness
• Oedema
• Friability, granular appearance
• Cobblestone-like (indicating deep inflammation)

Question 15

Endoscopy image of UC

Answer 15

Redness
Granular appearance
Friability (looks weak and easily bleeds)

Question 16

What are the primary complications of Crohn’s disease?

Answer 16

Strictures
Fissures

(others include malabsorption- anaemia; small bowel obstruction; abscess; bowel cancer; osteoporosis; lactose intolerance)

Question 17

What are strictures and how are they managed?

Answer 17

Narrowing of the bowel lumen causing obstruction and sudden pain

• can lead to haemorrhages and perforations
• identified through CT scans

TREATMENT

• Endoscopic balloon dilatation (remove)
• Strictureplasty (cut through and reshape)

Question 18

What are fistulae?

Answer 18

Abnormal passageway forming between one organ to another, or to the external environment

e.g. Enterocutaneous (bowel to skin); enteroenteric (bowel to bowel)

Question 19

What are the complications of UC?

Answer 19

• Electrolyte imbalance
• Toxic megacolon (acute swelling- can lead to fever/pain/sepsis)
• Severe bleeding (anaemia)
• Risk factor for colorectal cancer

Question 20

What extra intestinal diseases can result from IBD?

Answer 20

Uveitis
Osteoporosis
Ankylosing Spondylitis

Question 21

Differences between the clinical features of Crohn’s and uC?

Answer 21

Crohn’s

• Acute or gradual onset
• Weight loss, fever, malaise
• Anorexia
• Malabsorption and hypovitaminosis
• Frequent perianal disease (fistulae and abscess)
• Sometimes diarrhoea
• Abdominal pain and palpable tender masses (lumps in lower abdomen)

UC

• Abrupt onset
• Intense diarrhoea (with blood/mucus)
• Left sided pain (colon)
• Weightloss and anaemia
• Nausea and vomiting
• Dehydration
• Lower abdominal cramps and pain on defecation
• Fever

Question 22

Disease activity score used for Crohn’s?

Answer 22

Harvey Bradshaw Index

• Active disease when score is not stable and changes
• 24h recording factors such as abdominal pain, abdominal mass, wellbeing, number liquid stools

Question 23

Disease activity score used for UC?

Answer 23

Simple Clinical Colitis Activity Index (SCCAI)

- 24h recording urgency, blood/mucus in stools, general wellbeing, extracolonic frequency etc.

Question 24

What is used to determine activity and severity of CD/UC?

Answer 24

Disease activity scores
Endoscopies
History

Question 25

What else must be considered?

Answer 25

History
Blood Tests
Imaging
Stools culture
Faecal calprotectin