Colon Pathology Flashcards
What is the role of the small and large bowel?
Small - absorptive
Large - absorptive and secretory role
Describe the anatomy of the small bowel
Is approx. 6m long
Divided into duodenum, jejunum and ileum
Describe the anatomy of the large bowel
Caecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum
Describe the histology of the small bowel
3 cell types - goblet, columnar absorptive, endocrine
Crypts and villi
Cell renewed every 4-6days
Describe the histology of the large bowel
No villi, tubular crypts
Surface columnar absorptive cells and crypt goblet cells
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
Describe the control of the small and large bowel
Intrinsic - myenteric plexus
Extrinsic - autonomic innervation
What is included in the myenteric plexus?
Meissner’s and Auerbach’s plexus
What are some inflammatory bowel diseases?
Ulcerative colitis
Crohn’s Disease
Ischaemic and Radiation colitis
Appendicitis
Describe idiopathic inflammatory bowel disease
Chronic inflammatory conditions resulting from inappropriate and persistent activation of mucosal immune system by presence of normal intraluminal flora
Describe the aetiology of inflammatory bowel disease
Genetically susceptible
9% parent or sibling affected
NOD2 mutation associated with CD
HLA associations with UC
Describe the pathogenesis of inflammatory bowel disease
Strong immune response against normal flora which defects epithelial barrier function in genetically susceptible individuals
How is IBD diagnosed?
Clinical history, radiographic exam (CT abdomen) and pathological correlation
pANCA - autoimmune antibody which is not too specific
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
Who usually gets Ulcerative Colitis?
M=F
Peaks at 20-30 and 70-80 years old
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
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
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
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
