ACEM Primary
Gastrointestinal Pathology
Ischaemic Bowel Disease
- Bowel supplied by coeliac, SMA and IMA
- SMA/ IMA -> mesenteric arcades as approach intestinal wall + collateral from proximal coeliac and distal pudendal/ iliac circulations -> can tolerate progressive loss of blood supply
- Acute compromise of blood supply causes infarction
- Categories:
- Mucosal = extending to muscularis mucosa
- Mural = mucosa + submucosa
- Generally due to acute/chronic hypoperfusion secondary to shock, dehydration, cardiac failure or vasoconstrictive drugs
- Transmural = all layers of wall
- Generally due to acute vascular obstruction secondary to severe atherosclerosis, aortic aneurysm, hypercoagulable states, embolization of cardiac vegetations or aortic atheromas
- Pathogenesis:
- Initial hypoxic injury = onset of vascular compromise
- Reperfusion injury = greatest damage -> involve ROS, neutrophil infiltration and inflammation
- Distribution of damage:
- Watershed zones such as splenic flexure (SMA/IMA boundary) and sigmoid/rectum (IMA/ pudendal/ iliac boundary)
- Surface epithelium of intestine more susceptible
- Morphology:
- Mucosa stained with blood
- Atrophy and sloughing of surface epithelium
- Fibrous scarring of lamina if chronic
- Clinical features:
- Older patients with underlying vasculopathy
- Acute transmural = sudden severe abdominal pain, vomiting, bloody diarrhoea, shock
- Bacteria enter circulation as mucosal barrier breaks down = sepsis
- CMV infection causes ischaemic GI disease due to viral tropism for endothelial cells
- Radiation enterocolitis
- NEC
Inflammatory bowel disease
- Chronic condition due to inappropriate mucosal immune activation
- Takes two forms: Ulcerative Colitis and Crohn’s Disease
- Epidemiology:
- More common in females, teens to early 20s
- Caucasians and Ashkenazi Jews
- Pathogenesis results from a combination of:
- Intestinal microbiota
- Precise role to be defined
- Epithelial dysfunction
- Defects in epithelial tight junctions
- Aberrant mucosal immune responses
- TH1 and TH2 cells involved
- Intestinal microbiota
- Genetic predisposition
| Crohn’s Disease | Ulcerative Colitis | |
| Macroscopic: Bowel region Distribution Stricture Wall appearance | Ileum +/- colon Skip lesions Yes Thick | Colon and rectum only Continuous lesions Rare Thin |
| Microscopic: Inflammation Pseudo polyps Ulcers Lymphoid reaction Fibrosis Serositis Granulomas Fistulae/ sinuses | Transmural Moderate Deep, knife like Marked Marked Marked Yes (~35%) Yes | Submucosal and mucosal Marked Superficial Moderate Mild to none Mild to none No No |
| Clinical: Perianal fistula Fat/ vitamin malabsorption Malignant potential Recurrence after surgery Toxic megacolon | Yes in colonic disease Yes – Iron/Vitamin B12/protein With colonic involvement Common No | No No Yes No Yes |
| Symptoms: | Variable Intermittent attacks of diarrhoea, fever and abdominal pain Asymptomatic periods for weeks to months | Relapsing Bloody diarrhoea with strings of mucous, lower abdominal pain and cramps |
| Extra-intestinal manifestations: | Uveitis Migratory polyarthritis Sacroiliitis Ankylosing spondylitis Erythema nodosum Primary sclerosing cholangitis is less common | Peri cholangitis Primary sclerosing cholangitis (2.5- 7.5%) Others as for Crohn’s Disease |
Last Updated on August 25, 2021 by Andrew Crofton
Andrew Crofton
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