What type of CT (Computed Tomography) scan is best for showing mesenteric infarction?

CT Angiography (CTA) is the Best Imaging Modality for Mesenteric Infarction

CT Angiography (CTA) of the abdomen and pelvis is the first-line imaging test for suspected mesenteric infarction due to its high sensitivity (93-100%) and specificity (93-100%) for detecting vascular abnormalities and signs of bowel ischemia. 1, 2

Why CTA is Superior

• CTA is fast, accurate, and widely available, making it ideal for rapid diagnosis in this potentially life-threatening condition where early diagnosis is critical for patient survival 1, 2
• Triple-phase CTA protocol (non-contrast, arterial, and portal venous phases) is optimal as it allows evaluation of both arterial and venous patency 1
• CTA can simultaneously assess vascular findings (arterial stenosis, embolism, thrombosis, dissection, mesenteric vein thrombosis) and non-vascular findings (bowel wall thickening, hypoperfusion, dilatation, hemorrhage, mesenteric fat stranding, pneumatosis intestinalis, portal venous gas) 1
• 3D rendering capabilities of CTA assist in evaluating the vasculature and should be performed as part of the protocol 1
• CTA has been shown to improve patient survival through early and accurate diagnosis 1

Technical Considerations for CTA

• Both arterial and portal venous phases should be included in the protocol 1
• Neutral or negative oral contrast may be beneficial to better evaluate bowel wall thickening and enhancement, though this may not be possible in acute settings 1
• Non-contrast phase can help identify intramural hemorrhage and atherosclerotic calcifications, though some studies suggest it may not be required for accurate diagnosis 1
• CTA should be performed even in patients with renal insufficiency (GFR under 30) when mesenteric ischemia is suspected, as benefits of rapid diagnosis outweigh risks of contrast-induced nephropathy 1

Limitations of Other Imaging Modalities

Standard CT with IV Contrast (Venous Phase Only)

• Less well-studied compared to CTA for diagnosing mesenteric ischemia 1
• Can assess non-vascular findings and major arterial lesions but lacks arterial phase, leading to suboptimal evaluation of mesenteric arteries 1
• Diagnostic errors occur more frequently when relying on venous phase only 1
• Arterial phase has been shown to influence care in 19% of patients compared to portal venous phase alone 1

Non-contrast CT

• Limited value as it cannot demonstrate arterial filling defects or decreased bowel wall enhancement 1
• Can identify only late findings such as pneumatosis and portomesenteric gas, which are associated with more advanced ischemia and worse prognosis 1

MR Angiography (MRA)

• High sensitivity and specificity for diagnosing severe stenosis or occlusion at the origins of major vessels 1
• Limited role in diagnosing distal stenosis and non-occlusive mesenteric ischemia 1
• Long examination time may delay therapeutic options in acute settings 1
• Less likely to show ischemic findings within the bowel itself compared to CT 1

Conventional Angiography

• Historically the reference standard with sensitivity of 74-100% and specificity of 100% 1, 2
• Now primarily used as a complementary diagnostic tool with option for endovascular treatment 1, 2
• Should not be considered in patients with significant hypovolemia or hypotension 1
• Whether angiography should precede surgical intervention in the presence of peritoneal signs is controversial 1

Important Clinical Considerations

• Delayed diagnosis significantly increases mortality, which can approach 50% if untreated 1, 2
• CTA can help stratify patients to identify those who would benefit from angiography versus those who should undergo emergent surgery 1
• In patients with high clinical suspicion but negative CTA, conventional angiography should still be considered, particularly if distal disease is suspected 2
• Signs of peritonitis usually indicate infarcted bowel and may warrant immediate surgery rather than further imaging 1