Watershed vascular territories susceptible to ischaemia (splenic flexure, rectosigmoid)
Core concept
- Watershed = border zone between two arterial territories - perfused by the terminal branches of both, by neither well
- First to fail in hypoperfusion, last to be reached by collaterals
- Colon has two classical watersheds
- Splenic flexure = Griffiths' point - SMA (middle colic) / IMA (left colic)
- Rectosigmoid junction = Sudeck's point - IMA (sigmoid) / internal iliac (superior rectal vs middle rectal)
- Rectum is relatively spared - dual supply from IMA and internal iliac -> rectal involvement should prompt a rethink (infection, IBD, radiation)
3 more sections, plus exam facts
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