A 76-year-old man with atrial fibrillation not on anticoagulation presents with sudden-onset severe periumbilical pain, nausea, vomiting, and bloody diarrhea. Physical examination reveals a soft, non-tender abdomen. Serum lactate is 6.2 mmol/L. CT angiography shows an abrupt filling defect in the superior mesenteric artery (SMA) approximately 3 cm distal to its origin, with downstream small bowel wall thickening, mucosal hypoenhancement, and mesenteric edema. The structure marked **A** in the diagram demonstrates acute mesenteric ischemia from SMA embolism. Which of the following is the MOST appropriate next step in management?

Explanation

## Why Option 1 is correct The clinical presentation—sudden-onset pain out of proportion to physical findings, bloody diarrhea, elevated lactate, and CT angiography confirming SMA embolism with bowel ischemia—is diagnostic of acute mesenteric ischemia (AMI). The structure marked **A** (SMA embolus with bowel ischemia) represents the most time-critical surgical emergency in abdominal surgery. Per Sabiston and ACG guidelines, management mandates immediate resuscitation, broad-spectrum antibiotics (to cover gram-negative and anaerobes given risk of translocation), IV heparin to prevent propagation of thrombus, and URGENT vascular + general surgery consultation. Revascularization—either open embolectomy with exploratory laparotomy (gold standard if peritonitis or non-viable bowel) or endovascular therapy (catheter-directed thrombolysis, mechanical thrombectomy) for stable patients without peritonitis—must be initiated emergently. Every hour of delay increases mortality. The soft, non-tender abdomen suggests no peritonitis yet, making this patient a candidate for either approach, but the decision must be made immediately in the OR or interventional suite. ## Why each distractor is wrong - **Option 2**: While NPO status and IV fluids are part of initial resuscitation, vasopressors alone are inappropriate for SMA embolism. Vasopressors worsen nonocclusive mesenteric ischemia (NOMI) by reducing splanchnic flow; they are NOT a substitute for revascularization in embolic occlusion. This confuses NOMI management with embolic AMI. - **Option 3**: Observation and delayed imaging are contraindicated in acute embolic AMI. The diagnosis is already established by CT angiography; further delay allows progression to transmural infarction, perforation, and sepsis. Mortality at 60–80% is already high; waiting for "spontaneous resolution" is fatal. - **Option 4**: Warfarin is appropriate for secondary prevention (post-revascularization, to prevent recurrent embolism from AF), but it is NOT a substitute for acute revascularization. Oral anticoagulation has no role in the acute phase; IV heparin is required immediately to prevent thrombus propagation while revascularization is arranged. **High-Yield:** SMA embolism = sudden pain out of proportion to exam + cardioembolic source (AF, post-MI thrombus) + CT showing embolic occlusion distal to middle colic branch → EMERGENCY revascularization (embolectomy or endovascular) within hours; do NOT delay for observation or anticoagulation alone. [cite: Sabiston 21e — Mesenteric Vascular Disease; ACG Acute Mesenteric Ischemia Guidelines]