Colonic ischaemia typically affects areas supplied within the IMA perfusion territory, typically occurring at ‘watershed’ areas of large bowel, where there is ‘overlap’ or a physiological anastomosis between the IMA branches and the most distal branches of another blood supply (e.g. SMA).
Watershed Areas of Bowel
Splenic flexure (IMA and SMA overlap).
Sigmoid colon (IMA and pudendal artery overlap).
Caecum (ileocolic and ileal artery overlap).
Clinical Presentation
Transient reversible ischaemic colitis.
Chronic ischaemic colitis.
± stricture formation.
Acute total ischaemia (of a segment).
Necrosis.
Perforation.
Fulminant total necrosis (high mortality).
Aetiology
Atherosclerosis (>95%).
Ligation of IMA (e.g. AAA repair).
Intimal flap/dissection.
Trauma (e.g. iatrogenic).
Investigations
Contrast-enhanced CT.
Colonoscopy.
Barium enema.
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