Acute mesenteric ischemia
Acute mesenteric ischemia is an abrupt drop in small-bowel blood flow, most often superior mesenteric artery embolism, presenting as severe abdominal pain out of proportion to an unimpressive early examination. CT angiography confirms the diagnosis, and survival depends on immediate resuscitation, antibiotics, and anticoagulation followed by urgent revascularization or resection before infarction and peritonitis develop.
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What this article covers
- Overview
Definition: acute mesenteric ischemia (AMI) is a rare, abrupt decrease in blood flow to the small intestine, obstructive (arterial embolism or thrombosis, venous thrombosis) or nonobstructive (vasoconstriction of the mesenteric vasculature).
- Epidemiology
Dominant cause: embolic obstruction of the superior mesenteric artery accounts for about 80% of AMI; roughly 95% of emboli lodge in the SMA because of its caliber and the shallow angle at which it emerges from the aorta.
- Risk factors
Atrial fibrillation: the leading source of cardioembolism to the SMA.
- Pathophysiology
Occlusion or vasoconstriction interrupts perfusion: an embolus or thrombus mechanically occludes the SMA, or splanchnic vasoconstriction from shock or vasopressors reduces flow without a fixed…
- Clinical features
Pain out of proportion to examination: severe, constant periumbilical pain with an abdomen that is soft, nontender, and nondistended on early examination; this discordance is the single most important clue to early AMI.
- Differential diagnosis
Acute pancreatitis: epigastric pain radiating to the back with markedly elevated lipase, without the vascular risk factors or angiographic findings of AMI (acute pancreatitis).
- Diagnosis
Confirm with CT angiography, the recommended imaging modality for AMI: it directly visualizes an embolus or thrombus occluding the SMA, defines the extent of occlusion, and identifies infarction…
- Management
Resuscitate immediately: intravenous fluid resuscitation, correction of hypotension, nasogastric decompression for distension, and analgesia, started as soon as AMI is suspected and continued in parallel with imaging.
- Complications
Transmural bowel infarction and perforation: the dominant driver of mortality, with peritonitis and septic shock once the bowel wall is breached.
- Prognosis
Timing determines outcome: early recognition before infarction, when the examination is still soft and nontender, allows bowel-sparing revascularization and substantially better survival.
- Prevention
Anticoagulate atrial fibrillation per standard stroke-prevention criteria to reduce cardioembolic risk to the SMA (atrial fibrillation).
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