What is the recommended surveillance timeline for common iliac artery aneurysms and should I use Computed Tomography Angiography (CTA) or Ultrasound (US)?

Surveillance Timeline and Imaging Modality for Common Iliac Artery Aneurysms

For common iliac artery aneurysms, surveillance should be conducted every 6 months for aneurysms ≥3 cm using ultrasound as the primary imaging modality, with CTA reserved for pre-intervention planning or when ultrasound is inadequate. 1

Recommended Surveillance Timeline Based on Aneurysm Size

• For common iliac artery aneurysms measuring 2.0-2.9 cm in diameter:

  • Surveillance with ultrasound every 12 months 1
  • If stable over multiple years, interval may be extended 1

• For common iliac artery aneurysms measuring 3.0-3.4 cm in diameter:

  • Surveillance with ultrasound every 6 months 1, 2
  • More frequent monitoring is warranted as these aneurysms approach the intervention threshold 1

• For common iliac artery aneurysms ≥3.5 cm:

  • Elective repair is recommended rather than continued surveillance 1
  • This size represents the threshold for intervention to balance procedural risks with rupture risk 1

Imaging Modality Selection

• Ultrasound (US):

  • Recommended as the primary surveillance tool for common iliac artery aneurysms 1
  • Advantages include lower cost, no radiation exposure, and excellent correlation with CT measurements 2, 3
  • Ultrasound typically underestimates iliac aneurysm size by only 0.03 ± 0.06 cm compared to CT 2

• Computed Tomography Angiography (CTA):

  • Recommended when:
    • Aneurysm approaches intervention threshold (≥3.5 cm) 1
    • Pre-intervention planning is needed 1
    • Ultrasound imaging is inadequate or inconclusive 1
    • Aneurysm has saccular morphology which increases rupture risk 1
  • CTA provides superior anatomical detail needed for intervention planning 1

Growth Rate Considerations

• Average growth rate for common iliac artery aneurysms is approximately 1.5-2.9 mm/year 2, 3
• Smaller aneurysms (<3 cm) typically grow more slowly (0.11 ± 0.02 cm/year) 2
• Larger aneurysms (3-5 cm) grow more rapidly (0.26 ± 0.1 cm/year) 2
• Aneurysms showing rapid expansion (≥3 mm/year) warrant more frequent surveillance 1

Important Clinical Considerations

• Common iliac artery aneurysms frequently coexist with abdominal aortic aneurysms (20-40% of cases) 1
• Risk of rupture is rare for aneurysms <4 cm but increases significantly at larger sizes 1, 2
• Symptomatic aneurysms (pain, compression symptoms) warrant immediate intervention regardless of size 1
• When planning intervention, preservation of at least one hypogastric artery is crucial to prevent pelvic ischemia 1

Surveillance Protocol Implementation

• Use the same imaging technique and facility for consistency in measurements 1
• Document both maximum diameter and growth rate at each surveillance visit 1, 3
• Maintain standardized measurement techniques (anteroposterior and transverse diameters) 3
• Consider patient-specific factors that may accelerate growth (smoking, hypertension) 1

This surveillance approach balances the risk of rupture against the risks of intervention while minimizing radiation exposure and healthcare costs through appropriate use of imaging modalities.