Aortoiliofemoral and Lower-Extremity CT Angiography

A practical radiology review of Aortoiliofemoral and Lower-Extremity CT Angiography, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

• Purpose & Clinical Use
• CTA = rapid, comprehensive tool for PAD, trauma, post-EVAR, and infection.
• Evaluates inflow (aorta → iliacs), outflow (fem-pop), runoff (calf/foot)
• Guides revascularization, endovascular planning, or limb salvage.

Protocol Pearls

• kVp: 80–120 (↓kVp → ↑iodine attenuation)
• Contrast: ≥4 mL/s, bolus tracking (trigger 150 HU thoracic aorta).
• Coverage: diaphragm → toes.
• Delayed phase for bolus outrun / venous contamination.
• Dual-energy / PCD CT: virtual noncontrast, calcium removal, high-res 0.02 mm.

Anatomy & Collaterals

• Aorta → common iliac → internal/external iliac → CFA → SFA → popliteal → tibials.
• Key collaterals: Winslow pathway, cruciate anastomosis, deep femoral perforators.
• Recognize variants (persistent sciatic artery, popliteal branching).
• Peripheral Arterial Disease
• Atherosclerotic occlusion = most common (85%).
• Grading: mild < 50%, mod 50–74%, severe 75–99%, occluded 100%.
• Embolic disease → multiple abrupt occlusions, renal/splenic infarcts.
• PAA: >50% diameter ↑; repair if >20 mm.

Postintervention Findings

• Bypass grafts: look for stenosis, thrombosis, pseudoaneurysm, infection.
• Stents: assess patency, fractures, in-stent stenosis (use VMI to reduce blooming).

Trauma Spectrum

• Active bleed = enlarging blush arterial → delayed phase.
• Pseudoaneurysm = stable rounded focus, no change delayed.
• Occlusion/transection = abrupt cutoff ± no distal flow.
• Dissection = thin intimal flap, “web-like.”
• Vasospasm = transient, improves on f/u.
• AVF = early venous filling; differentiate from hyperemia.

Other Pathologies

• Infectious pseudoaneurysm / graft infection → rim enhancement + gas.
• Buerger disease → distal occlusion + corkscrew collaterals.
• Cystic adventitial disease → fluid attenuation around artery.
• Popliteal entrapment → medial deviation/compression of artery.

Interpretation Tips

• Use structured template (aorta → runoff, both sides).

Include inflow/outflow/runoff classification, stenosis %, length, collaterals, target vessels.

• Don’t skip nonvascular findings — up to 15% are clinically important!
• Key Takeaways
• Tailor protocol to indication (EVAR, trauma, PAD).
• Always verify bolus timing.
• Exploit spectral/PCD CT for artifact reduction & contrast saving.
• Integrate clinical context for embolic vs. atherosclerotic patterns.
• Structured, succinct reporting = clinical clarity.