Inflammatory bowel disease (colon pathology) Flashcards
What are the sections of the large bowel and how are they peritonised?
Caecum (retroperitoneal)
Ascending colon (Retroperitoneal)
Transverse colon (Intraperitoneal)
Descending colon (Retroperitoneal)
Sigmoid colon (Intraperitoneal)
Rectum (retroperitoneal)
What 3 cell types are most present in the small bowel?
Goblet cells
Columnar absorptive cells
Endocrine cells
What types of cells are found in crypts in the small intestine?
Stem cells Goblet cells Endocrine cells Paneth cells
How long does the process of cell renewal take in the small intestine?
4-6 days
How is the basic mucosal structure of the large bowel different to the small bowel?
Flat with no villi Tubular crypts On the surface, there is only columnar absorptive cells In the crypts, there are goblet cells, endocrine cells and stem cells (no cells of Paneth)
Neuromuscular control of the small/large bowel involves both intrinsic and extrinsic control What are these control mechanisms?
Intrinsic control is via the myenteric plexus Extrinsic control is through autonomic innervation
What are the 2 parts of the myenteric plexus?
Meissener’s plexus - around the base of the submucosa
Auerbach plexus - between the inner circular and outer longitudinal layers of the muscularis propria
What is idiopathic inflammatory bowel disease?
Chronic inflammatory conditions arising from inappropriate and persistent activation of the mucosal immune system - driven by the presence of normal intraluminal flora
What are the 2 types of idiopathic inflammatory bowel diseases?
Ulcerative colitis
Crohn’s
Crohn’s disease and Ulcerative colitis are in many ways similar, but have a couple of key differences What is the difference between where they can be located?
Crohn’s can affect anywhere from the mouth to anus. Ulcerative colitis is limited only to the colon
Is family history important in Crohn’s patients?
Yes 15% have affected 1st degree relatives
Lifetime risk if either a parent or sibling is affected is 9%
What gene mutation is associated with Crohn’s disease?
NOD2
What gene mutations are associated with Ulcerative colitis?
HLA genes
What overall is believed to cause Crohn’s and Ulcerative colitis?
Strong immune response against normal flora with defects in the epithelial barrier function in genetically susceptible individuals
What is the role of intestinal flora in development of Crohn’s and UC?
No specific microbe has been identified
Defects in mucosal barrier could allow microbes access to mucosal lymphoid tissue triggering immune response
How are Inflammatory bowel diseases diagnosed?
Clinical history
Radiographic examination
Pathological correlation
What is pANCA, and why is useful in the diagnosis in some IBDs?
Perinuclear antineutrophilic cytoplasmic antibody (pANCA)
positive in 75% of UC patients BUT only 11% of CD patients (so not that useful for Crohn’s)
Describe the epidemiology of Ulcerative colitis
Male = Female frequency
More common in 20-30 and in 70-80 year olds
What are the types (by area) of ulcerative colitis?
Large bowel:
What is backwash ileitis?
Inflammation in the distal ileum thought to be due to “backwash” of cecal contents
(patients with pancolitis may develop this)
What is the prevalence of ‘Pancolitis’?
10% of UC patients
What other small part of the alimentary canal can be involved in UC?
Appendix
When does the large bowel look like in a patient with ulceratie colitis?
Continous pattern of inflammation from rectum proximally
Presence of Pseudoplyps and ulcers
What are pseudopolyps?
Pseudopolyps are projecting masses of scar tissue that develop from granulation tissue during the healing phase in repeated cycle of ulceration
How does Ulcerative colitis affect the mucosal surface of an affected area?
Inflammation obviously
Cryptitis, Dissaray of crypts, Crypt abscesses
Mucosal atrophy
How does Ulcerative colitis affect the submucosal layer of the affected area?
Ulceration into submucosa- pseudopolyps
Limited mainly to mucosa and submucosa
NO granulomas
Submucosal fibrosis
What is the link between Ulcerative colitis and cancer?
Increases risk of cancer
If pancolitis > 10years then increased risk of colon cancer by 20-30x
What complications are associated with Ulcerative colitis?
Cancer
Haemorrhage
Perforation
Toxic dilatation
Describe the epidemiology of Crohn’s disease
Females > males
Peaks 20-30 and 60-70 years old but can manifest at any age including children (@nick diston)
Most common in caucasians especially the Jewish
Where is Crohn’s most likely to affect?
40% Small intestine (especially the end of the SI)
30% SI and LI
30% Colon
What is the difference between Crohn’s and UC in terms of the layers of the Gut tube affected?
In UC - Only the mucosa and sometimes the Sub mucosa are affected
In Crohn’s - All 4 layers of gut tube inflammed
What specific type of inflammation is present in Crohn’s and not in UC?
Crohn’s features non-caseating Granulomas
UC does not have Granulomas
Describe the pathological appearance of Crohn’s
Alternating ‘skip lesions’ with Thickened, oedematous wall and ‘cobblestone ulceration’
Affected areas may feature:
structuring
Granular serosa / dull grey
Wrapping mesenteric fat
Mesentry- thickened, oedematous and fibrotic (more fibrosis than UC)
What are the main histological features of Crohn’s affected tissue?
Cryptitis & crypt abscesses
Architectural distortion
Crypt atrophy/destruction
*Non-caseating granulomas*
*Transmural inflammation* - ‘chain of pearls’
Fibrosis
Lymphangiectasia (dilation of lymph vessels)
Hypertrophy of mural nerves
Paneth cell metaplasia
What main histological differences are specific to Crohn’s and not UC?
NC Granulomas
Transmural inflammation (C of P)
Lymphangiectasia
Hypertrophy of mural nerves
What are the long term effects of crohn’s on the affected area?
Malabsorption of SI (if affected)
Stricture / narrowing
Fistulas, abscess formation & perforation
Increased risk of cancer
The wall appearance in Crohn’s is ______ whereas in Ulcerative colitis it is _______
Crohn’s = thickened
UC = Thinner
Ischaemic enteritis can affect what parts of the digestive tract?
Small or large intestine (or both)
Ishcaemic enteritis can lead to infarction if there is acute occlusion of what arteries?
Coeliac
Superior mesenteric
Inferior mesenteric
(these are the 3 major supply vessels)
Why would gradual occlusion of the supply vessels (such as the coeliac artery) be unlikely to cause ischaemia?
Anastomotic circulation means there are alternative routes for arterial supply
How common is mesenteric venous occlusion compared to arterial occlusion of the gut?
Less common
What layers of the gut tube would be affected in a major vessel occlusion?
Ischaemic enteritis through major vessel occlusion would cause transmural injury (all layers)
What types of conditions would predispose someone to ischaemic enteritis?
Arterial thrombosis (atherosclerosis, hypercoagulable states, oral contraceptives etc)
Arterial embolism (atheroembolisms, vegatations etc)
Non-occlusive ischaemia (cardiac failure, shock etc)
(full list on ppt)
How would acute ischaemia appear histologically?
Oedema
Interstitial haemorrhages
Sloughing necrosis of mucosa-ghost outlines
Nuclei indistinct
Initial absence of inflammation
1-4 days – bacteria-gangrene and perforation
Vascular dilatation
What are the main patholical effects of chronic ischaemia?
Mucosal and Submucosal inflammation
Ulceration and Fibrosis
Strictures
Why does radiation cause inflammation of the colon?
Abdominal irradiation can impair the normal proliferative activity of the small and large bowel epithelium
Dividing cells are especially at risk of damage
What area of the digestive tract most commonly gets radiation colitis and why?
Rectum - due to pelvic radiotherapy
What are the symptoms of radiation colitis?
Anorexia
Abdominal cramps
Diarrhoea
Malabsorption
Chronic RC has similar symptoms of IBD
What histological changes are seen in radiation colitis?
Inflammation - crypt abscesses and EOSINOPHILS
Arterial stenosis (late)
Ulceration, necrosis, haemorrhage, perforation
What is the difference between the appendix in young and old people?
In young people there is prominent lymphoid tissue
This regresses with age
What causes appendicits?
Obstruction:
- Pinworm (Enterobius vermicularis)
- Feocolith (stones made of hardened faeces)
Appendicits can cause increased intralumenal pressure
What can this lead to?
Local ischaemia
What macroscopic features are present in appendicitis?
fibrinopurulent exudate
perforation
abscess
What microscopic features are present in appendicits?
Acute suppurative inflammation in wall and pus in lumen
Acute gangrenous-full thickness necrosis +/- perforation
