Pathology of Colon 1 - IBD Flashcards
Two divisions of the enteric nervous system and where they are located?
Meissener’s / Auerbach’s plexus - base of the submucosa
Myenteric plexus - between inner circular muscle layer and out longitudinal muscle layer
What is inflammatory bowel disease?
Chronic inflammatory conditions resulting from inappropriate activity of the gut immune system against normal intraluminal flora
Main idiopathic inflammatory bowel diseases?
Ulcerative colitis
Crohn’s disease
How do Crohn’s disease (CD) and ulcerative colitis (UC) differ?
- 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
Gene mutation associated with Crohn’s?
NOD2
Gene mutation associated with UC?
HLA (major histocompatibility complex)
Antibody test that can be used to help diagnose UC?
pANCA (perinuclear antineutrophilic cytoplasmic antibody)
Positive in 75% of UC patients
Only positive in 11% of Crohn’s patients
When does UC peak in a patient? Crohn’s?
UC - peaks at 20-30yrs and 70-80yrs
CD - peaks at 20-30yrs and 60-70yrs
Can the appendix be involved in ulcerative colitis?
Yes
Where can UC manifest? What are the main colonic signs?
In the large bowel, continuous pattern of inflammation from rectum to proximal
Signs are ulceration and pseudopolyps
- minimal/no serosal inflammation
What are the main histological signs of UC? What layers are involved?
Main signs are:
- crypt abscesses/dissarray
- ulceration into the submucosa
- submucosal fibrosis
Limited mostly to mucosa and submucosa
What is pancolitis?
Form of ulcerative colitis that affects the entire large intestine
Appearance of the serosa in Crohn’s? Of the mesentery?
Granular - dull grey
Fat wrapped mesentery. Mesentery itself is thickened, oedematous and fibrotic
What does the lumen of the Crohn’s bowel look like?
Narrow
Sharp demarcations between healthy and diseased tissue called “skip lesions”
Deep ulceration (cobblestone)
Non-caseating granulomas
How is the inflammation in Crohn’s different from that of UC?
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
What histological feature is useful for differentiating CD and UC?
The presence/absence of non-caseating granulomas
Present in Crohn’s, not in ulcerative colitis
Long term complications of Crohn’s?
- Malabsorption in SI
- Strictures
- Fistulas and abscesses
- Perforation
- Increased risk of cancer (5x)
What is ischaemic enteritis?
Inflammation/injury of the SI due to lack of adequate blood flow
LI involvement?
What causes infarction in the bowel?
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
How does major blood vessel occlusion in the bowel differ in consequence from acute/chronic hypoperfusion?
Major blood vessel occlusion causes transmural injury
Hypoperfusion causes mucosal +/- submucosal injury
Predisposing conditions for ischaemia?
Arterial thrombosis - atherosclerosis, vasculitis, dissecting aneurysm, oral contraceptives
Arterial embolism - cardiac vegetations, acute atheroembolism, cholesterol embolism
Non-occlusive ischaemia - cardiac failure, dehydration, vasoconstrictive drugs
Which area of the colon is vulnerable to acute ischaemia?
Splenic flexure
Fewest anastomosing collaterals
Consequences of chronic bowel ischaemia?
- Mucosal inflammation
- Ulceration
- Submucosal inflammation
- Fibrosis
- Stricture
What is radiation colitis?
Injury to the small/large bowel epithelium due to radiation (often radiation therapy)
Which cells are most vulnerable to radiation colitis?
Targets dividing cells - blood vessels and crypt epithelium at high risk
Occurs in rectum often - pelvic radiotherapy
Symptoms of radiation colitis?
Anorexia
Abdominal cramps
Diarrhoea
Malabsorption
Histological changes observed from radiation colitis?
Bizarre cellular changes
- inflammation, crypt abscesses and eosinophils
- ulceration
- necrosis
- Haemorrhage/perforation
What is appendicitis?
Acute inflammation of the appendix
Histology of appendicitis?
Macro - fibrinopurulent exudate, perforation & abscesses
Micro - Suppuritive inflammation in wall, pus in lumen
