Is it possible to perform a computed tomography (CT) angiogram of the legs?

CT Angiography of the Legs: Feasibility and Clinical Applications

Yes, CT angiography (CTA) of the lower extremities is absolutely possible and is a well-established, widely available imaging modality for evaluating leg vasculature. 1

Technical Capabilities

CTA of the lower extremities can be performed with or without imaging the abdomen and pelvis, depending on clinical needs:

• Isolated leg CTA can be performed when aortoiliac disease is not a concern or when the status of proximal vessels is already known 1
• Multidetector CT scanners enable rapid scanning of the entire arterial system from abdomen through feet using helical and multistation axial acquisitions 1
• Volumetric acquisition allows extensive postprocessing including multiplanar reformatted and maximum-intensity projection images to create detailed arterial road maps 1

Diagnostic Performance

CTA demonstrates excellent accuracy for lower extremity vascular assessment:

• Sensitivity and specificity of 90-100% for detecting stenoses greater than 50% diameter when compared to catheter angiography 1
• For traumatic vascular injury, CTA shows 96.2% sensitivity and 99.2% specificity, with 100% sensitivity and specificity reported in some prospective studies 1, 2
• Superior to duplex ultrasound in clinical utility and accuracy for bypass graft assessment 1

Clinical Indications

Peripheral Arterial Disease

• Diagnosis and localization of anatomic stenosis in patients with claudication or critical limb ischemia 1
• Pre-procedural planning for both endovascular and surgical revascularization 1
• Assessment of collateral vessels and arteries distal to occlusions that may not appear on catheter angiography 1

Trauma

CTA is recommended when one or more of the following findings are present 1:

• External bleeding of arterial origin
• Injury site near a main vascular axis
• Presence of non-expanding hematoma
• Isolated neurological deficit
• Ankle-brachial index (ABI) less than 0.9

Other Indications

• Acute limb ischemia from thrombosis or embolism 3
• Aneurysms and pseudoaneurysms 4
• Arteriovenous fistulas 2

Advantages Over Alternative Imaging

Compared to MRA, CTA offers 1:

• More rapid acquisition time
• Better safety in patients with pacemakers or defibrillators
• Less severe artifacts from metallic implants
• Minimal issues with claustrophobia

Compared to duplex ultrasound 1:

• Cross-sectional imaging shows nonvascular findings
• Better visualization of proximal vessels and collaterals
• Less operator-dependent

Important Limitations and Pitfalls

Technical Challenges

• Heavy arterial calcification can limit interpretation, particularly in tibial arteries 1
• Patients at highest risk for nondiagnostic studies include those over 80 years old, diabetics, and dialysis patients 1
• Dual-energy CTA can reduce blooming and beam-hardening artifacts from calcification and metallic stents 1

Contraindications and Cautions

• Renal dysfunction limits use due to iodinated contrast requirement 1
• Contrast allergy requires pretreatment or alternative imaging 1
• Radiation exposure, though less than catheter angiography 1

Timing Considerations

• Asymmetric opacification may occur with proximal stenoses, potentially obscuring arterial phase in some vessels 1
• Time-resolved CTA techniques can improve diagnostic confidence and reduce venous overlay in the lower legs 5

Guideline Recommendations

The American College of Cardiology/American Heart Association provides Class IIb recommendations (may be considered) for 1:

• Diagnosing anatomic location and presence of significant stenosis in lower extremity PAD
• Substituting for MRA in patients with MRA contraindications

The American College of Radiology gives higher appropriateness ratings for CTA in peripheral arterial disease evaluation, particularly for revascularization planning 1

Practical Algorithm

For suspected peripheral arterial disease 1:

1. Begin with ankle-brachial index and duplex ultrasound
2. Proceed to CTA for anatomic detail when revascularization is contemplated
3. Consider MRA instead if severe renal dysfunction or heavy calcification expected

For trauma with vascular injury concern 1:

1. Assess for hard signs (active bleeding, expanding hematoma, absent pulses)
2. Measure ABI if feasible
3. Proceed directly to CTA if ABI <0.9 or hard signs present
4. CTA has replaced conventional angiography as first-line imaging