Colon Pathology Flashcards by Sophie Pitcairn

What is the role of the small and large bowel?

Small - absorptive
Large - absorptive and secretory role

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Describe the anatomy of the small bowel

Is approx. 6m long
Divided into duodenum, jejunum and ileum

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Describe the anatomy of the large bowel

Caecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum

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Describe the histology of the small bowel

3 cell types - goblet, columnar absorptive, endocrine
Crypts and villi
Cell renewed every 4-6days

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Describe the histology of the large bowel

No villi, tubular crypts
Surface columnar absorptive cells and crypt goblet cells

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Explain the intestinal immune system

GIT is a large surface area for exposure to environmental antigens
Must balance ingested harmful substances against defence reactions to potential microbial invaders

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Describe the control of the small and large bowel

Intrinsic - myenteric plexus
Extrinsic - autonomic innervation

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What is included in the myenteric plexus?

Meissner’s and Auerbach’s plexus

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What are some inflammatory bowel diseases?

Ulcerative colitis
Crohn’s Disease
Ischaemic and Radiation colitis
Appendicitis

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Describe idiopathic inflammatory bowel disease

Chronic inflammatory conditions resulting from inappropriate and persistent activation of mucosal immune system by presence of normal intraluminal flora

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Describe the aetiology of inflammatory bowel disease

Genetically susceptible
9% parent or sibling affected
NOD2 mutation associated with CD
HLA associations with UC

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Describe the pathogenesis of inflammatory bowel disease

Strong immune response against normal flora which defects epithelial barrier function in genetically susceptible individuals

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How is IBD diagnosed?

Clinical history, radiographic exam (CT abdomen) and pathological correlation
pANCA - autoimmune antibody which is not too specific

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What is ulcerative colitis?

Inflammatory bowel disease which is localised to the rectum (proctitis) but more commonly spreads proximally
Associated with systemic symptoms - nausea, anaemia

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Who usually gets Ulcerative Colitis?

M=F
Peaks at 20-30 and 70-80 years old

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Describe the pathology of ulcerative colitis

Large bowel only
Continuous pattern of inflammation
Can get pseudo-polyps and ulceration
Serosal surface has minimal or no inflammation

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Describe the histology of ulcerative colitis

Mucosa inflammation
Cryptitis and crypt abscesses
Architectural disarray of crypts
Mucosal atrophy
No granulomas
Ulceration limited to mucosa and submucosa

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Explain ulcerative colitis and risk of cancer

Is reactive dysplasia
Which can be classified high or low grade
Flay epithelial atypia - adenomatous change - invasive cancer

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What are some complications of UC?

Haemorrhage
Perforation
Toxic dilatation - colon expands rapidly so can cause infection

What is Chron’s Disease?

Inflammatory bowel disease at any level of GIT from mouth to anus
Has systemic manifestations - nausea, anaemia, malabsorption

Who can get Chron’s Disease?

More females than males
Peaks at 20-30 and 60-70 years old
More common in Caucasians and Jewish population

Describe the pathology of Chron’s Disease

Granular serosa/ dull grey
Wrapping mesenteric fat
Mesentery is thickened and fibrotic
Thick wall so narrowed lumen
Ulceration looks like cobblestone

Describe the histology of Chron’s Disease

Cryptitis and crypt abscesses
Architectural distortion
Ulceration is deep
Non-caseating granulomas

What are some long term features of Chron’s Disease?

Small intestine malabsorption
Strictures
Fistulas and abscesses
Perforation
Increased risk of cancer

What is ischaemic enteritis?

Can be restricted to either SI or LI or affect both depending of vessel affected

What vessel occlusion can lead to infarction?

Coeliac, inferior and superior mesenteric arteries Gradual occlusion can have little effect - anastomotic circulation

In ischaemic enteritis what happens if major vessel occlusion?

Transmural injury Acute/ Chronic hypoperfusion

What are some predisposing conditions for Ischaemia?

Arterial thrombosis Arterial embolism Non-occlusive ischaemia - cardiac failure, shock, vasoconstrictive drugs

Describe acute ischaemia in ischaemic enteritis

Splenic flexure venerable Early intense congestion - dusky purple pink Lumen - sanguineous (dying) mucin

Describe the histology of acute ischaemia

Oedema and interstitial haemorrhages Sloughing necrosis of outlines 1-4days then gangrene and perforation Nuclei indistinct

Describe chronic ischaemia

Mucosal and submucosal inflammation, ulceration, fibrosis and stricture

Describe radiation colitis

Abdominal irradiation can impair the normal proliferation activity of small and large bowel epithelium Usually rectum

Describe the pathogenesis of radiation colitis

Damage depends on dose Targets actively dividing cells esp. blood vessels and crypt epithelium

What are the symptoms of radiation colitis?

Anorexia, abdominal cramps, diarrhoea and malabsorption

Describe the histology of radiation colitis

Bizarre cellular changes Inflammation crypt abscesses Ulceration, necrosis, haemorrhage and perforation

Describe appendicitis

Acute inflammation Causes obstruction and increased intraluminal pressure - ischaemia

Describe the histology of appendicitis

Macro-fibro purulent exudate, perforation, abscess Micro- acute inflammation and pus in lumen Can get acute gangrenous and full thickness necrosis

Describe dysplasia

Adenoma (polyps) - tubular, villous, tubulovillous 50% are solitary

What is low grade dysplasia?

Increased nuclear no. and size Reduced mucin Darker epithelium and still looks like glands

What is high grade dysplasia?

Crowded, very irregular, not yet invasive

What are the risk factors of colorectal adenocarcinoma?

Lifestyle, FH, IBD, genetics - FAP, HNPCC

What are the features of right sided colorectal adenocarcinoma?

Exophytic/ polypoid, anaemia, vague pain, weakness and obstruction Can grow large before obstruction as more liquid going through

What are the features of left sided colorectal adenocarcinoma?

Annular - napkin ring lesion, bleeding is more fresh, altered bowel habit and obstruction is more likely

What does colorectal cancer prognosis depend on?

Tumour grade Tumour stage Extramural venous invasion Resection