Pathology of Colon 1 - IBD

Question 1

Two divisions of the enteric nervous system and where they are located?

Answer 1

Meissener’s / Auerbach’s plexus - base of the submucosa

Myenteric plexus - between inner circular muscle layer and out longitudinal muscle layer

Question 2

What is inflammatory bowel disease?

Answer 2

Chronic inflammatory conditions resulting from inappropriate activity of the gut immune system against normal intraluminal flora

Question 3

Main idiopathic inflammatory bowel diseases?

Answer 3

Ulcerative colitis

Crohn’s disease

Question 4

How do Crohn’s disease (CD) and ulcerative colitis (UC) differ?

Answer 4

• Crohn’s can affect GIT from mouth to anus, UC is limited to the colon
• Crohn’s has presence of non-caseating granulomas on histology
• Crohn’s has skip lesions whereas UC is diffuse
• CD has transmural inflammation, UC limited to mucosa & submucosa

Question 5

Gene mutation associated with Crohn’s?

Answer 5

NOD2

Question 6

Gene mutation associated with UC?

Answer 6

HLA (major histocompatibility complex)

Question 7

Antibody test that can be used to help diagnose UC?

Answer 7

pANCA (perinuclear antineutrophilic cytoplasmic antibody)

Positive in 75% of UC patients
Only positive in 11% of Crohn’s patients

Question 8

When does UC peak in a patient? Crohn’s?

Answer 8

UC - peaks at 20-30yrs and 70-80yrs

CD - peaks at 20-30yrs and 60-70yrs

Question 9

Can the appendix be involved in ulcerative colitis?

Answer 9

Yes

Question 10

Where can UC manifest? What are the main colonic signs?

Answer 10

In the large bowel, continuous pattern of inflammation from rectum to proximal

Signs are ulceration and pseudopolyps
- minimal/no serosal inflammation

Question 11

What are the main histological signs of UC? What layers are involved?

Answer 11

Main signs are:

• crypt abscesses/dissarray
• ulceration into the submucosa
• submucosal fibrosis

Limited mostly to mucosa and submucosa

Question 12

What is pancolitis?

Answer 12

Form of ulcerative colitis that affects the entire large intestine

Question 13

Appearance of the serosa in Crohn’s? Of the mesentery?

Answer 13

Granular - dull grey

Fat wrapped mesentery. Mesentery itself is thickened, oedematous and fibrotic

Question 14

What does the lumen of the Crohn’s bowel look like?

Answer 14

Narrow
Sharp demarcations between healthy and diseased tissue called “skip lesions”
Deep ulceration (cobblestone)
Non-caseating granulomas

Question 15

How is the inflammation in Crohn’s different from that of UC?

Answer 15

In UC inflammation mainly limited to mucosa and submucosa - is also diffuse

In Crohn’s inflammation is transmural (across all layers of the wall) - skip lesions

Question 16

What histological feature is useful for differentiating CD and UC?

Answer 16

The presence/absence of non-caseating granulomas

Present in Crohn’s, not in ulcerative colitis

Question 17

Long term complications of Crohn’s?

Answer 17

• Malabsorption in SI
• Strictures
• Fistulas and abscesses
• Perforation
• Increased risk of cancer (5x)

Question 18

What is ischaemic enteritis?

Answer 18

Inflammation/injury of the SI due to lack of adequate blood flow

LI involvement?

Question 19

What causes infarction in the bowel?

Answer 19

Acute ischaemia due to occlusion of one of the major 3 blood supply vessels (coeliac, sup/inf mesenteric)

gradual occlusion can have little effect - accounted for by anastomotic circulation

Question 20

How does major blood vessel occlusion in the bowel differ in consequence from acute/chronic hypoperfusion?

Answer 20

Major blood vessel occlusion causes transmural injury

Hypoperfusion causes mucosal +/- submucosal injury

Question 21

Predisposing conditions for ischaemia?

Answer 21

Arterial thrombosis - atherosclerosis, vasculitis, dissecting aneurysm, oral contraceptives

Arterial embolism - cardiac vegetations, acute atheroembolism, cholesterol embolism

Non-occlusive ischaemia - cardiac failure, dehydration, vasoconstrictive drugs

Question 22

Which area of the colon is vulnerable to acute ischaemia?

Answer 22

Splenic flexure

Fewest anastomosing collaterals

Question 23

Consequences of chronic bowel ischaemia?

Answer 23

• Mucosal inflammation
• Ulceration
• Submucosal inflammation
• Fibrosis
• Stricture

Question 24

What is radiation colitis?

Answer 24

Injury to the small/large bowel epithelium due to radiation (often radiation therapy)

Question 25

Which cells are most vulnerable to radiation colitis?

Answer 25

Targets dividing cells - blood vessels and crypt epithelium at high risk

Occurs in rectum often - pelvic radiotherapy

Question 26

Symptoms of radiation colitis?

Answer 26

Anorexia
Abdominal cramps
Diarrhoea
Malabsorption

Question 27

Histological changes observed from radiation colitis?

Answer 27

Bizarre cellular changes

• inflammation, crypt abscesses and eosinophils
• ulceration
• necrosis
• Haemorrhage/perforation

Question 28

What is appendicitis?

Answer 28

Acute inflammation of the appendix

Question 29

Histology of appendicitis?

Answer 29

Macro - fibrinopurulent exudate, perforation & abscesses

Micro - Suppuritive inflammation in wall, pus in lumen