What aneurysm diameter warrants treatment of a common iliac artery aneurysm or an internal iliac (pelvic) artery aneurysm?

Treatment Threshold for Iliac Artery Aneurysms

Elective repair is recommended when common iliac artery aneurysms reach 3.5 cm in diameter, and the same 3.5 cm threshold applies to internal iliac (hypogastric) artery aneurysms. 1, 2

Evidence-Based Size Thresholds

Common Iliac Artery Aneurysms

• The 2022 ACC/AHA guidelines establish 3.5 cm as the repair threshold for common iliac artery aneurysms, balancing procedural risks against rupture risk. 3, 1

• No iliac aneurysm ≤3.8 cm ruptured in a large case series of 438 patients followed for a mean of 3.7 years, supporting the safety of surveillance below the 3.5 cm threshold. 3, 1

• The median diameter of ruptured iliac aneurysms at presentation is 6.8 cm, indicating substantial safety margin below 3.5 cm. 3, 1

• Elective repair at a median size of 4.3 cm was documented in the Dutch Surgical Aneurysm Audit, though the guideline-recommended threshold is 3.5 cm to prevent progression to higher-risk territory. 3

Internal Iliac (Hypogastric) Artery Aneurysms

• Internal iliac artery aneurysms ≥3.5 cm warrant elective repair using the same threshold as common iliac aneurysms. 2

• Rupture below 4 cm is rare but documented: in a multinational review, 1 patient had rupture ≤3 cm and 4 patients had ruptures ≤4 cm, justifying the 3.5 cm intervention threshold. 3, 2

• The slightly higher rupture risk at smaller diameters for internal iliac aneurysms compared to common iliac aneurysms supports not delaying repair beyond 3.5 cm. 2

Surveillance Protocol Below Treatment Threshold

Size-Stratified Monitoring

• For aneurysms measuring 2.0–3.0 cm, annual duplex ultrasound surveillance is appropriate, as rupture at these sizes is exceedingly rare and average growth is approximately 2.9 mm per year. 1, 4

• For aneurysms measuring 3.0–3.5 cm, increase surveillance frequency to every 6–12 months with duplex ultrasound, as they approach the repair threshold. 1, 2, 4

• CT angiography should be obtained as size approaches 3.5 cm for pre-intervention planning and anatomic detail. 1, 2, 4

Accelerated Growth Criteria

• If an aneurysm expands rapidly (≥5 mm in 6 months or ≥10 mm in 1 year), shorten surveillance intervals to every 3–6 months and consider early intervention regardless of absolute size. 1

• Document maximum diameter and growth rate at each visit, as accelerated growth may warrant earlier intervention even below the 3.5 cm threshold. 2

Critical Clinical Exceptions

Symptomatic Aneurysms

• Any symptomatic iliac aneurysm (abdominal pain, back pain, pulsatile mass, neurologic symptoms) requires immediate surgical evaluation and intervention regardless of size. 1, 2

Concomitant Aortic Disease

• Screen all patients with iliac aneurysms for abdominal aortic aneurysm (AAA), as 20–40% have coexisting AAA and 86% of common iliac aneurysm patients have current or previously treated AAA. 3, 2, 4

• When both iliac and aortic aneurysms are present, the iliac aneurysm may reach repair threshold before the AAA, requiring comprehensive treatment planning for the entire aortoiliac system. 2, 4

Important Procedural Considerations

Internal Iliac Artery Preservation

• Preservation of at least one internal iliac artery is crucial during repair to prevent pelvic ischemia complications. 3, 2

• Unilateral internal iliac artery exclusion causes buttock claudication in 27% of patients, bilateral exclusion in 36%, and erectile dysfunction in 10% of men. 3, 2

• Spinal cord, bowel, and gluteal ischemia occur at rates <1% but represent devastating complications requiring individualized treatment planning with shared decision-making. 3

Landing Zone Planning

• Common iliac arteries ≥18 mm in diameter have significantly higher rates of type Ib endoleaks (7.2% vs 3.2%) and late reinterventions (19% vs 11.8%) after EVAR, influencing graft selection and landing zone planning. 3, 4

Common Pitfalls to Avoid

• Do not delay repair once the 3.5 cm threshold is reached—rupture risk rises substantially with continued observation. 1, 2

• Do not rely solely on diameter measurements—symptomatic presentation mandates immediate evaluation regardless of size. 1, 2

• Do not perform isolated iliac repair without comprehensive imaging of the entire aortoiliac system, as concomitant disease is common and may require simultaneous treatment. 2, 4

• Avoid fluoroquinolone antibiotics in patients with iliac aneurysms unless absolutely necessary, as they may accelerate aneurysm growth. 1