GIT Pathology Flashcards
What conditions can lead to infarction of bowel?
- Acute arterial occlusion: atherosclerosis, aortic aneurysm, hypercoagulable state, OCP, embolism
- Intestinal hypoperfusion: cardiac failure, shock, dehydration, vasoactive drugs • Systemic vasculitis: HSP, Wegener’s granulomatosis
- Mesenteric venous thrombosis: hypercoagulable state, invasive neoplasm, cirrhosis, trauma
- Misc: radiation, volvulus, stricture, amyloid, diabetes
What parts of the bowel are most susceptible to ischaemic injury and why?
Watershed zones - splenic flexure, sigmoid colon, rectum - located at end of arterial supply
Surface epithelium: villi more at risk than crypts
Intestinal capillaries run from crypts up villi to surface
What is the pathogenesis of ischaemic bowel injury?
- Initial hypoxic injury
- Secondary reperfusion injury: - major injury in this phase - free radical production, neutrophil infiltration, inflammatory mediator release
- Magnitude of response determined by:
- vessel affected
- timeframe over which ischaemia develops
What is the causative organism of cholera?
Vibrio cholerae, Gram negative bacteria (comma shaped, flagellate) typically transmitted by drinking contaminated water
Describe the pathogenesis of cholera
- Non-invasive organisms
- Flagellar proteins important for epithelial attachment and efficient bacterial colonisation
- V. cholera produces cholera toxin that is internalised after binding enterocyte surface GM1 gangliosides:
- Toxin A subunit processed in ER
- To toxin A fragment which stimulates adenylate cyclase by activating G protein
- Causing surge in cytosolic cAMP which opens CFTR
- Releasing Cl ions into lumen - Na/HCO3 secretion with obligate water, leading to massive diarrhoea (up to 1L/hr of rice-water diarrhoea)
What features differ between Crohn Disease and Ulcerative Colitis?
Macro:
- CD - ileum ± colon, skip lesions, strictures, thick walled appearance
- UC - colon only, diffuse distribution, strictures rare, thin walled appearance
Micro:
- CD - transmural inflammation, deep, kniefe-like ulcers, marked lymphoid reaction and fibrosis, granulomas, fistulae/sinsues
- UC - mucosal inflammation, marked pseudopolyps, superficial, broad based ulcers, no granulomas or fistulae/sinuses
Clinical:
- CD - perianal fistula (colonic disease), fat/vitamin malabsorption, malignant potential only with colonic disease, recurrence after surgery common
- UC - increased malignant potential, toxic megacolon
Compare and contrast the extraintestinal manifestations of CD and UC
Both: migratory polyarthritis, sacroiliitis, ankylosing spondylitis, uveitis, cholangitis
CD: erythema nodosum, amyloidosis
UC: primary sclerosing cholangitis, skin lesions, colonic adenocarcinomas
