Acute Mesenteric Ischaemia

Interruption of the mesenteric blood supply — embolic (classically AF), thrombotic on existing atherosclerosis, non-occlusive in a low-flow state, or venous. Mortality is high and is driven almost entirely by delay to diagnosis. The trap is that the…

Pain Out of Proportion

The pathway

1 · Recognise the mismatch

Severe pain that is out of proportion to the examination findings — the single most useful feature
Sudden onset in embolic disease; more insidious with postprandial pain and weight loss in thrombotic disease
Vomiting and diarrhoea early; peritonism is a late sign and means infarction
Risk: AF, recent MI, known vascular disease, heart failure, low-output states, vasopressors, thrombophilia

A soft abdomen in a distressed patient should raise suspicion, not lower it.

2 · Resuscitate

ABCDE, large-bore access, generous IV fluid resuscitation (these patients are profoundly volume-depleted)
Catheterise and monitor urine output
Analgesia — opioids, and do not withhold them
NBM, NG tube if vomiting or distended
Correct electrolytes; expect metabolic acidosis

3 · Bloods — and what they don't tell you

FBC (raised WCC), U&E, LFT, amylase, lactate, clotting, group & save, VBG/ABG
A normal lactate early on does not exclude mesenteric ischaemia. Lactate rises once bowel is infarcting — it is a late marker, not a screening test
The same is true of a normal WCC and a soft abdomen
ECG — looking for AF as the embolic source

4 · CT angiography — the test

CT angiography of the mesenteric vessels is the investigation. Arterial phase imaging is needed, so say what you are looking for when you request it — a routine portal-venous abdominal CT can miss the occlusion.

Do not delay imaging to wait for bloods, and do not accept a plain film as a negative test.

5 · Involve surgery now

Discuss with the surgical registrar at the point of suspicion, not after the CT report
Vascular surgery and interventional radiology may both be needed
Broad-spectrum antibiotics per local policy once the diagnosis is suspected — bacterial translocation across ischaemic bowel is expected
Options: embolectomy, revascularisation (open or endovascular), resection of non-viable bowel, and often a planned second-look laparotomy

6 · Non-occlusive disease is different

Non-occlusive mesenteric ischaemia happens in low-output states — cardiogenic shock, sepsis on vasopressors, post-cardiac-surgery, dialysis. There is no clot to remove.

Treatment is optimising perfusion: treat the cause of the low flow, reduce vasoconstrictors where possible, and involve ITU. Surgery is reserved for infarcted bowel.

Drugs

Drug	Dose	Route	Notes
IV crystalloid	500ml boluses	IV	Reassess after each. These patients are usually severely fluid-depleted.
Morphine	Titrated	IV	Do not withhold analgesia for fear of masking signs — the signs are unreliable anyway.
Broad-spectrum antibiotics	Per local policy	IV	Local antimicrobial guidance overrides any national default. Translocation is expected once bowel is ischaemic.
Unfractionated heparin	Per local protocol	IV	Often started after discussion with vascular surgery — not an F1 decision on your own.

When to escalate

Suspected mesenteric ischaemia at all — surgical registrar now, before imaging is reported,Peritonism or free air — emergency laparotomy,Rising lactate or worsening acidosis — infarcting bowel, escalate immediately,Shock — ITU alongside surgery,Known AF with sudden severe abdominal pain — treat as embolic until disproven

Reference: Written against general UK surgical practice; no single NICE guideline covers acute mesenteric ischaemia. Follow local vascular and surgical protocols.

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