From the Guidelines
A CTA should be ordered without delay in any patient with suspicion for acute mesenteric ischemia (AMI), as recommended by the World Society of Emergency Surgery 1.
Importance of Prompt CTA Ordering
The decision to order a CTA is critical in the diagnosis and management of AMI, as delay in diagnosis is a significant factor contributing to high mortality rates of 30–70% despite increased knowledge of this entity 1. Every 6 hours of delay in diagnosis, which is essentially a delay in performing CTA, doubles mortality 1.
Diagnostic Approach
The multidetector CTA has become the diagnostic study of choice, replacing formal angiography, and is particularly useful for its ability to provide detailed images of the vascular structures, aiding in the identification of thrombi, embolisms, or other vascular abnormalities 1. The use of volume rendering and multiplanar reconstructions (MPR) enhances the diagnostic capability, especially in assessing the origin of the mesenteric arteries and detecting signs of bowel ischemia or infarction 1.
Key Considerations
- Comprehensive Biphasic CTA: This includes pre-contrast scans, arterial and venous phases, and multiplanar reconstructions to thoroughly assess the vascular and bowel structures 1.
- Contrast Use: CTA should be performed despite the presence of acute kidney injury, as the risks associated with delayed diagnosis far outweigh those of contrast exposure 1.
- Radiological Findings: Specific radiological findings such as bowel loop dilatation, pneumatosis intestinalis, and portal vein thrombosis are predictive of bowel necrosis and guide the urgency of intervention 1.
Clinical Application
In clinical practice, the suspicion of AMI should prompt immediate consideration for CTA, given its high sensitivity and specificity for diagnosing this condition 1. The clinical significance of certain radiological findings, such as pneumatosis intestinalis, must be interpreted in the context of the patient's overall clinical picture, as these findings can sometimes be associated with benign conditions 1.
Conclusion is not needed as per the guidelines, the above information is sufficient to answer the question.
From the Research
When to Order CTA
- The decision to order a Computed Tomography Angiography (CTA) depends on various factors, including the clinical presentation and suspicion of underlying vascular pathology 2, 3, 4, 5, 6.
- In patients with suspected acute stroke, CTA can be useful in identifying large vessel occlusion, high-grade stenoses, or occlusions, and guiding triage to the appropriate target hospital and specialized treatment 4, 5.
- CTA can be performed in the prehospital setting using a mobile stroke unit, allowing for rapid identification of vascular abnormalities and facilitating triage decisions 4.
- The safety of CTA in the evaluation of patients with acute stroke has been demonstrated, with no significant difference in renal function or delay in therapy delivery compared to non-contrasted head computed tomography (NCHCT) alone 5.
- In patients with transient ischemic attack (TIA) or minor stroke, CTA can help identify those at high risk for recurrent stroke and guide management decisions, including the use of dual antiplatelet therapy 2, 6.
- The timing of CTA ordering depends on the clinical scenario, but it is generally recommended to perform CTA as soon as possible after symptom onset, ideally within 24 hours, to guide management decisions and improve outcomes 6.