What are the next steps for a patient with a prominent left common iliac artery found on ultrasound?

Management of Prominent Left Common Iliac Artery on Ultrasound

The critical first step is to determine whether this finding represents an iliac artery aneurysm (≥1.5 cm diameter) or is simply describing the arterial anatomy in relation to potential venous compression—obtain precise diameter measurements and assess for associated venous pathology. 1, 2

Immediate Assessment Required

Measure the Arterial Diameter Precisely

• If the common iliac artery diameter is ≥1.5 cm, this meets criteria for an iliac artery aneurysm (IAA) and requires specific management protocols 2
• Request exact measurements from the ultrasound report—"prominent" is insufficient for clinical decision-making 3
• If measurements are not provided, order a dedicated duplex ultrasound of bilateral lower extremities including iliac segments, or proceed directly to CTA 1, 4

Assess for Venous Compression Syndrome

• A prominent left common iliac artery may be compressing the underlying left common iliac vein (May-Thurner syndrome or nonthrombotic iliac vein lesion) 5, 6
• Look for clinical signs of chronic venous disease: unilateral left leg swelling, chronic aching, varicosities, skin changes, or history of left-sided DVT 5
• Check the ultrasound report for venous findings: lack of respiratory phasicity in the common femoral vein Doppler waveform suggests proximal venous obstruction 5

Diagnostic Algorithm Based on Clinical Context

If Arterial Aneurysm is Suspected (Diameter ≥1.5 cm)

Order CTA of abdomen and pelvis with bilateral lower extremity runoff 1, 4

• CTA provides 90-100% sensitivity and specificity for detecting significant stenoses and defining aneurysm anatomy 4
• This imaging determines: exact aneurysm size, involvement of internal iliac artery, status of contralateral internal iliac artery, and proximal neck characteristics 3

Management thresholds for iliac artery aneurysms: 2

• IAA <3 cm: Annual surveillance with ultrasound (expansion rate 0.11 cm/year)
• IAA 3-3.5 cm: Surveillance ultrasound every 6 months (expansion rate 0.26 cm/year)
• IAA ≥3.5 cm: Consider elective repair in good-risk patients
• IAA ≥4 cm or any symptomatic IAA: Recommend operative repair (all symptomatic patients in one series had IAA >4 cm)

If Venous Compression is Suspected (Symptoms of Chronic Venous Disease)

Obtain CTA or MR venography to evaluate for iliac vein compression 5, 4

• CT venography can identify anatomic compression, though 24% of asymptomatic patients show >50% diameter compression of the left iliac vein 5
• MR venography demonstrates 90% sensitivity for nonthrombotic iliac vein lesions (NIVL) 5
• If whole-leg swelling is present with normal compression ultrasound of the femoropopliteal veins, imaging of the iliac and pelvic veins is warranted 5

If cross-sectional imaging confirms significant compression and symptoms are present: 5

• Consider catheter-based venography with intravascular ultrasound (IVUS) for definitive diagnosis
• IVUS diameter reduction >61% at the lesion significantly predicts clinical success with intervention 5
• Treatment involves venous stenting if hemodynamically significant compression is confirmed 7

If Arterial Occlusive Disease is Suspected (Claudication Symptoms)

Obtain resting ankle-brachial index (ABI) bilaterally—this is the highest-rated initial test (9/9) 8, 1

• Critical caveat: Resting ABIs are frequently normal in isolated iliac disease 5, 1
• If resting ABI is normal but symptoms suggest iliac disease, perform exercise/treadmill ABI testing 1, 4
• Exercise ABIs unmask hemodynamically significant proximal disease that appears normal at rest 1

Order CTA abdomen and pelvis with bilateral lower extremity runoff 1, 4

• Provides complete anatomic detail from aorta through lower extremities in a single study 1
• Enables accurate identification of stenosis location and severity 4
• Determines suitability for endovascular versus surgical intervention 1

Alternative if CTA contraindicated: 1, 4

• Duplex ultrasound has 92% sensitivity and 96% specificity for detecting significant aortoiliac lesions
• Excellent negative predictive value (97-100%) reliably excludes significant disease
• However, positive predictive value is only 60-89%, so positive findings may require CTA confirmation

Common Pitfalls to Avoid

• Do not rely on the term "prominent" without obtaining actual measurements—this descriptor is clinically meaningless without dimensions 2, 3
• Do not assume normal resting ABIs exclude iliac arterial disease—exercise testing is essential 5, 1
• Do not dismiss unilateral left leg symptoms as simple venous insufficiency—May-Thurner syndrome requires specific imaging and treatment 5, 6
• Do not order venography as a first-line test—it is now reserved for cases where intervention is planned 4