Should I obtain imaging of the iliac arteries in a patient with a known abdominal aortic aneurysm (AAA) who has a faint left femoral pulse on physical examination?

Imaging of Iliac Arteries in a Patient with Known AAA and Faint Left Femoral Pulse

Yes, you should obtain imaging of the iliac arteries in a patient with known AAA and faint left femoral pulse, as this clinical finding strongly suggests iliac artery involvement that requires evaluation with CT angiography (CTA). 1, 2

Rationale for Iliac Artery Imaging

• A faint femoral pulse in a patient with known AAA suggests possible extension of aneurysmal disease or stenotic/occlusive disease in the iliac arteries, which could significantly impact treatment planning and patient outcomes 1, 2
• Approximately 5% of AAAs are juxtarenal or suprarenal, and iliac artery involvement is common in AAA patients, making comprehensive imaging essential 1
• Iliac artery aneurysms frequently coexist with abdominal aortic aneurysms and may not be adequately visualized by ultrasound alone 3
• The American College of Radiology recommends that imaging of the iliac arteries should be included when evaluating AAA patients due to the close correlation between aortic and iliac pathology 1

Recommended Imaging Approach

• CTA is the optimal choice for pre-intervention studies and is considered the reference standard for AAA diagnosis and management decision-making 1, 2
• CTA provides high-resolution imaging of the aorta and its branch vessels with submillimeter, isotropic, 3-D datasets that allow for accurate assessment of both the AAA and iliac arteries 1
• The scan range should include the iliofemoral arteries to evaluate access vessels, which is particularly important given the faint femoral pulse finding 1
• CTA allows for proper measurement of the outer-to-outer (OTO) aortic diameter perpendicular to the long axis of the aorta, which is the recommended measurement technique 1, 2

Alternative Imaging Options

• If CTA is contraindicated (e.g., severe renal dysfunction or contrast allergy):
  • MR angiography (MRA) with IV contrast is an acceptable alternative for evaluating iliac arteries and AAA 1, 2
  • Non-contrast MRA techniques are available for patients with renal insufficiency, though they have limitations including longer acquisition times and increased motion artifacts 1
  • Catheter arteriography has very limited utility and should only be considered when both CTA and MRA are contraindicated 1

Clinical Implications

• Detecting iliac artery involvement is crucial for determining whether a tubular or bifurcated repair is needed for the AAA 4
• A faint femoral pulse may indicate stenosis, occlusion, or aneurysmal disease of the iliac arteries that could complicate surgical or endovascular repair 5
• Failure to identify iliac artery pathology could lead to incomplete treatment planning and potentially catastrophic outcomes, as complications of iliac aneurysm rupture can be lethal 3
• Complete evaluation of both the AAA and iliac arteries provides all necessary preoperative information for optimal surgical or endovascular planning 6

Common Pitfalls to Avoid

• Relying solely on ultrasound may lead to underestimation of aneurysm size (typically by 4mm compared to CTA) and inadequate visualization of iliac arteries 1, 2
• Failing to use multiplanar reformatted images for tortuous aneurysms can result in artifactual accentuation of a single dimension 1
• Not including the full extent of the iliofemoral system in imaging studies can miss critical information about access vessels for potential endovascular repair 1
• Overlooking associated vascular anomalies that may be present alongside AAA and iliac artery disease 7