A 62-year-old woman with atrial fibrillation presents with sudden severe abdominal pain out of proportion to physical findings. She has a metabolic acidosis with raised lactate. CT angiography shows occlusion of the superior mesenteric artery 3 cm distal to its origin with opacification of the main trunk proximally. The most likely mechanism is:

• A Non-occlusive mesenteric ischaemia from low flow
• B Embolic occlusion of the SMA ✓
• C Thrombosis of an atherosclerotic plaque at the SMA origin
• D Mesenteric venous thrombosis

Explanation

Occlusion several centimetres beyond the SMA origin in a patient with atrial fibrillation is typical of embolism, which lodges 3 to 10 cm distal to the origin where the vessel narrows, often sparing the proximal jejunal branches. Atherosclerotic thrombosis occurs at the ostium with collateral development and a prodrome of weight loss and food fear. Non-occlusive ischaemia shows diffuse spasm without a discrete cut-off, and venous thrombosis shows portal or mesenteric vein filling defects.

Reference: Schwartz's Principles of Surgery, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.