What CT scan is indicated for a patient with suspected AAA (abdominal aortic aneurysm) presenting with abdominal pain and hypotension?

From the Guidelines

CT scan with intravenous (IV) contrast is indicated for a patient with suspected AAA presenting with abdominal pain and hypotension.

Key Considerations

• The choice of imaging modality should be based on the patient's history, clinical presentation, and institutional availability 1.
• CT scan is widely available, quick to perform, and can diagnose the underlying AAA, as well as show the full extent of the dissection and vessel patency 1.
• CT scan with IV contrast is preferred, but noncontrast CT can be used if there is a contraindication to iodinated contrast 1.

Imaging Modalities

• CT abdomen and pelvis with IV contrast is the recommended initial imaging modality for suspected AAA, as it provides accurate assessment of aortic diameter and can detect complications such as malperfusion and hemopericardium 1.
• Noncontrast CT can be used as an alternative, especially in patients with a history of iodinated contrast reaction or those who are too unstable to receive contrast 1.
• Other imaging modalities, such as US, MRI, and aortography, may be used in specific clinical circumstances, but are not the first-line choice for initial imaging 1.

From the Research

CT Scan Indications for Suspected AAA

The following CT scans are indicated for a patient with suspected abdominal aortic aneurysm (AAA) presenting with abdominal pain and hypotension:

• Computed Tomography with Angiography (CTA) is the most appropriate imaging modality, as it has a sensitivity of 91.4% and specificity of 93.6% for diagnosis of ruptured AAA 2
• Contrast-enhanced CT angiography is currently considered the gold standard for preoperative imaging and image-based treatment planning in AAA repair 3
• CT scan can help identify patients with a confined rupture, unstable aneurysm, non-aneurysmal cause of pain, and stable AAA, allowing for optimal preoperative evaluation and semielective surgical treatment 4

Key Findings

• CTA has reasonable accuracy for diagnosing ruptured AAA, but may miss some cases 2
• CT scan can classify patients with symptomatic AAA into those who need emergency surgery and those who do not 5
• Imaging findings of rupture, impending rupture, and other abdominal aortic abnormalities can be identified using CT scan 6

Imaging Strategies

• Ultrasound is the mainstay imaging modality for AAA screening and surveillance, but CT angiography is preferred for preoperative imaging and treatment planning 3
• Non-contrast MR angiography and 3D imaging with multiplanar reformation can also be used for accurate assessment of aortic diameters 3