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Acute mesenteric ischaemia and ischaemic colitis
Severe abdominal pain that far exceeds the findings of a "soft" examination, in a patient with atrial fibrillation or atherosclerosis, is mesenteric ischaemia until proven otherwise; every hour of delay costs bowel, so CT angiography is done at once and flow is restored before the bowel dies.
Why it matters in the exam
The classic case is an older patient with atrial fibrillation who arrives with severe abdominal pain, vomiting and diarrhoea, while the abdomen is barely tender on examination. Questions check that you recognise the gap between pain and examination, that you are not reassured by a normal lactate or blood count, and that the right test is urgent CT angiography — without waiting for the creatinine. Then you must separate four mechanisms: embolism to the superior mesenteric artery (cardiac source), thrombosis on atherosclerosis (often with a history of post-prandial pain, fear of eating and weight loss), non-occlusive ischaemia (NOMI — in a shocked patient or one on vasoconstrictors) and venous thrombosis (thrombophilia).
Treatment is tested by mechanism: heparin, fluids and antibiotics for all; revascularisation (surgical or endovascular) and resection of dead bowel for embolism and arterial thrombosis, sometimes with a "second-look" operation after 24–48 hours; treating the cause and an intra-arterial vasodilator infusion in NOMI; and anticoagulation for venous thrombosis, with surgery only for peritonitis. A related topic is ischaemic colitis — in the "watershed" areas (the splenic flexure and the rectosigmoid junction), with mild pain and bloody diarrhoea, which mostly settles with conservative treatment.
Key points
- Pain out of proportion to the examination + atrial fibrillation or atherosclerosis = mesenteric ischaemia until proven otherwise.
- CT angiography at once; a normal lactate does not exclude it.
- Embolism and arterial thrombosis: heparin, revascularisation and resection of dead bowel; second look after 24–48 hours.
- NOMI — treat the cause and give a vasodilator; venous thrombosis — anticoagulation.
- Ischaemic colitis — splenic flexure and sigmoid, usually conservative treatment.
Summary table
| Mechanism | Typical background | CT finding | Treatment |
|---|---|---|---|
| Arterial embolism | Atrial fibrillation, recent myocardial infarction; sudden pain | Occlusion of the superior mesenteric artery some distance from its origin | Heparin, clot removal (open or endovascular), resection of dead bowel |
| Arterial thrombosis | Atherosclerosis, past post-prandial pain and weight loss | Occlusion at the origin of the artery with calcification | Heparin, revascularisation (stent or bypass), resection of dead bowel |
| Non-occlusive ischaemia (NOMI) | Shock, vasoconstrictor drugs, dialysis, cardiac surgery | Patent but narrow, spastic arteries | Treat the cause, stop vasoconstrictors, intra-arterial vasodilator; surgery if there is necrosis |
| Mesenteric venous thrombosis | Thrombophilia, younger patient, gradual pain | Clot in the superior mesenteric vein and bowel wall oedema | Anticoagulation; surgery only for peritonitis or necrosis |
| Ischaemic colitis | Older patient, hypotension, after aortic surgery | Wall thickening at the splenic flexure or sigmoid | Support and fluids, usually no surgery; surgery for necrosis or perforation |
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Sources
- ESVS Clinical Practice Guidelines on the Management of Diseases of Mesenteric Arteries and Veins, 2017 — Acute mesenteric ischaemia: diagnosis and treatment
- WSES guidelines on acute mesenteric ischemia (update), 2022 — Diagnosis, revascularisation and second-look surgery
- Sabiston Textbook of Surgery, 21st edition (2022) — Mesenteric Vascular Disease
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.