Pathology of the Bowel Flashcards
What are the two different examples of IBD?
Ulcerative colitis
Crohn disease
What is an example of inflammatory intestinal diseases?
Inflammatory bowel disease
What are examples of colonic polyps and neoplastic diseases?
Non-neoplastic
Neoplastic
What is the histology of the normal colonic mucosa?
It has crypts containing abundant goblet cells that secrete mucin
What else is present in normal histology of the colon?
Underlying submucosa
Small nodules of gut-associated lymphoid tissue
What is IBD?
It is a chronic condition
Complex interactions of a genetically susceptible host, defective mucosal barrier, intestinal dysbiosis, and dysregulated immune response
What is the result of IBD?
Inflammation of the bowel
What are the main types of IBD?
Crohn Disease and ulcerative colitis
What is the incidence of Crohn disease?
70 to 150 per 100000 people per year
Which areas of the GIT does Crohn involve?
Any area of the GIT
Frequently transural
What is the incidence of ulcerative colitis?
20 to 40 per 100000
Which areas does ulcerative colitis affect?
Colon and rectum only
Which layers does ulcerative colitis extend to?
Into mucosa and submucosa
What is one of the causes of IBD?
It is unknown but it can be familial
What is the distribution like of both IBD types?
Crohn –> skip lesions
UC –> Diffuse
What is the stricture like of both IBD types?
Crohn –> yes
UC –> rare
What is the bowel wall appearance of both IBD types like?
Crohn –> thick
UC –> thin
What is the inflammation like in both IBD types?
Crohn –> transmural
UC –> mucosa and submucosa
What are the pseudopolyps of both IBD types like?
Crohn –> moderate
UC –> marked
What are the ulcers in both IBD types like?
Crohn –> Deep, knife-like
UC –> superficial, broad-based
What is the lymphoid reaction in both types od IBD like?
Crohn –> marked
UC –> moderate
What is fibrosis like in both types of IBD like?
Crohn –> marked
UC –> mild to none
Which IBD type has serosistis?
Crohn
Which IBD type has granulomas?
Crohn (35%)
Which IBD type has fistulas?
Crohn
In which IBD type is there fat/vitamin malabsorption?
Crohn
What is the malignant potential of both IBD types, like?
Crohn –> if the colon is involved
UC –> yes
What is the recurrence after surgery with both types of IBD?
Crohn –> common
UC –> no
Which IBD type can have the clinical presentation of toxic megacolon?
UC
What is the genetic risk associated with Crohn?
NOD2
Autophagy related genes (ATG16L1, IRGM)
What is the pathogenesis when it comes to the genetic risk of Crohn?
Ineffective at defending against intestinal bacteria
Bacteria are able to enter through the epithelium into wall of intestine
Trigger inflammatory reactions
What is the mucosal immune response like in IBD?
TH1 type is well recognised in Crohn
TH2 is well recogenised in UC
What mediates TH1?
IL12,
IFN-γ
TNF
What mediates TH2?
Natural killer cells
What are the epithelial defects of IBD?
Disease-associated NOD2 polymorphisms
Barrier dysfunction can activate innate and adaptive mucosal immunity
What factors modify the composition of the microbial population?
Diet and disease
What is the pathogenesis of IBD?
Repeated cycle by which transepithelial flux of luminal bacteria components activate innate and adaptive immune responses
What is the pathogenesis of IBD like in a susceptible host?
Subsequent release of TNF and other immune signs
Directs epithelia to increase tight junction permeability
Further increases the flux of luminal material
Establish a self-amplifying cycle in which a stimulus at any site may be sufficient to initiate IBD
Explain the pathogenesis of IBD (from the diagram) ?
Bacterial components enter the cell, Caught up by dendritic cells
IL23 is released, also IL8 is released and secretes neutrophils
HLA2-TCR connection is made and casues T cell proliferation (TH17, TH2, TH1)
IL23 activates TH17 cells which secrete Il17 and recruit neutrophils
TH2 secrete IL13
T cells become TH1 through IL12, and they then secrete IFN-γ which recruits macrophages
TNF and IL13 act on epithelial barrier
What are the macroscopic features of Crohn? (5)
Regional enteritis
Skip lesions
Aphthous ulcer
Cobblestone appearance
Fissures
Where does regional enteritis arise?
Any area of the GIT
1. Small intestine –> 40%
2. Small intestine & colon –> 30%
3. Colonic involvement only –> 30%
What are skip lesions?
The presence of multiple & separate areas of disease
What is an aphthous ulcer?
Edema and loss of normal mucosal folds
What is the cobblestone appearance?
Diseased tissue is depressed below the level of normal mucosa
Where do fissures usually develop with Crohn?
Between mucosal folds and may extend deeply to become sites of perforation or fistula tracts
What are the macroscopic features of Crohn?
- Intestinal wall is thickened
- Intestinal lumen is narrowed (early cases) and combination of edema and fibrosis (long standing cases)
- Nodular swelling, fibrosis and mucosal ulceration –> cobblestone appearnce
- Extensive transmural disease –> mesenteric fat frequency extends around serosal surface
What causes stenosis of intestinal lumen in early cases of Crohn?
Edema
What are the microscopic features of Crohn’s?
Crypt abscess
Ulceration
Repeated cycles of crypt destruction
What are crypt abscesses?
Abundant neutophils that infiltrate and damage crypts
What are the results of repeated cycles of crypt destruction?
Distortion of mucosal architecture
Epithelial metaplasia
Paneth cell metaplasia
Noncaseating granulomas