Superior Mesenteric Artery (SMA) Thrombosis: Diagnosis and Treatment
Diagnostic Approach
Contrast-enhanced CT angiography (CTA) is the gold standard diagnostic test for SMA thrombosis and should be performed urgently in any patient with suspected acute mesenteric ischemia. 1
Key Diagnostic Features
- CTA demonstrates proximal SMA occlusion with calcified atherosclerotic plaque in thrombotic cases, distinguishing it from embolic occlusion which typically shows an abrupt cutoff without significant atherosclerosis 1
- Perform biphasic imaging (arterial and venous phases) with 1mm slices for optimal diagnostic accuracy, which approaches 94% sensitivity and 95% specificity 1
- D-dimer should be measured to help rule out the diagnosis when negative (96% sensitivity), though it lacks specificity (40%) 1
- Elevated lactate indicates advanced disease with bowel gangrene already present, not early ischemia 1
Clinical Presentation Clues
- Patients typically have prior symptoms of chronic mesenteric ischemia (postprandial pain, weight loss, food aversion), other atherosclerotic manifestations, and smoking history—distinguishing thrombosis from embolism 1, 2
- Pain out of proportion to physical examination is the hallmark finding 1
- Absence of peritoneal signs suggests viable bowel and a window for revascularization 1
Treatment Algorithm
For Acute SMA Thrombosis WITHOUT Peritoneal Signs
Endovascular therapy with angiography, transcatheter thrombolysis, followed by percutaneous transluminal angioplasty and stent placement is the first-line treatment (appropriateness rating 8/9). 1
- Systemic anticoagulation (rating 8/9) must be initiated as an adjunct to surgical or transcatheter treatment 1, 3
- Endovascular approaches reduce bowel resection requirements, lower mortality, and decrease short bowel syndrome incidence compared to surgery alone 1, 4
- Sequential intermittent thrombolytic therapy with angiographic evaluation at 24,36, and 48 hours can achieve complete recanalization in early-stage occlusions 5
- Catheter-directed vasodilator infusion should be considered to address associated vasospasm 1
For Acute SMA Thrombosis WITH Peritoneal Signs
Immediate surgical exploration is mandatory when peritoneal signs, pneumoperitoneum, or intramural air are present, as these indicate bowel infarction. 1, 6
- Surgical endarterectomy or bypass (rating 6/9) is performed if endovascular approach is not technically feasible 1
- Intraoperative Doppler ultrasound of the SMA should be performed during surgery to confirm arterial flow and detect new thrombosis 7
- Second-look laparotomy is often required 24-48 hours later to reassess bowel viability 6, 7
Critical Timing Considerations
Time to diagnosis is the most important predictor of outcome—mortality approaches 50% overall but improves dramatically with early intervention within 5-10 hours of symptom onset 1, 5, 6
Post-Intervention Management
- Follow-up CTA at one month should be performed to assess SMA patency 4
- Long-term anticoagulation is essential given the thrombotic etiology and underlying atherosclerotic disease 1, 3
- Evaluate for prothrombotic disorders (protein S deficiency, antithrombin III deficiency) in younger patients or those without typical atherosclerotic risk factors 7
Common Pitfalls to Avoid
- Do not delay CTA for elevated creatinine—the risk of missing mesenteric ischemia far outweighs contrast nephropathy concerns 1
- Do not rely on plain abdominal X-rays—normal findings do not exclude the diagnosis 1
- Do not attempt thrombolysis if bowel infarction cannot be confidently excluded—this has limited widespread use of purely endovascular approaches 1
- In hemodialysis patients with diabetes and abdominal pain, maintain extremely high suspicion for SMA thrombosis as this population has particularly high mortality 4