What is the management approach for multiple small cystic lesions in the right popliteal fossa surrounding the right popliteal artery?

Management of Multiple Small Cystic Lesions in the Right Popliteal Fossa

The primary diagnosis to establish is whether these represent cystic adventitial disease (CAD) versus popliteal artery aneurysm with mural thrombus, as this fundamentally determines management—CAD may be treated with cyst excision alone while aneurysms ≥2.0 cm require bypass grafting. 1

Initial Diagnostic Workup

Obtain duplex ultrasound immediately to characterize the cystic lesions, measure the popliteal artery diameter, assess for stenosis or occlusion, and evaluate for mural thrombus. 2, 3, 4 The ultrasound should specifically:

• Measure the popliteal artery diameter at its widest point (aneurysm defined as ≥2.0 cm or twice normal diameter for age/gender) 2, 1
• Identify whether cysts are within the arterial wall (adventitial) versus surrounding structures 4
• Document presence or absence of intraluminal thrombus 1
• Assess flow dynamics and degree of stenosis 4

Screen for bilateral disease and associated aneurysms with imaging of the contralateral popliteal artery and abdominal aorta, as 50% of popliteal aneurysms are bilateral and 50% have associated abdominal aortic aneurysms. 1, 5

Differential Diagnosis Considerations

If Popliteal Artery Aneurysm (≥2.0 cm diameter):

Proceed directly to surgical repair regardless of symptoms, as aneurysms ≥2.0 cm have a 14% complication rate versus 3.1% for smaller aneurysms, with 50% becoming symptomatic within 2 years and 75% within 5 years. 1, 5 Delaying repair until symptoms develop results in 56% experiencing persistent distal ischemia and 19% requiring amputation due to prior emboli destroying runoff vessels. 1

• Surgical approach: Bypass with saphenous vein graft (superior long-term patency compared to synthetic grafts) 1, 5
• If acute thrombosis with absent runoff occurs, perform catheter-directed thrombolysis or mechanical thrombectomy first to restore distal vessels before definitive repair 2, 1, 5

If Cystic Adventitial Disease (CAD):

CAD presents as mucin-containing cysts in the adventitial layer causing arterial compression, typically in young to middle-aged men without atherosclerotic risk factors. 3, 6 Key distinguishing features include:

• Hypoechoic cystic lesions surrounding or within the arterial wall on ultrasound 3, 4
• Crescent-shaped cysts compressing the lumen eccentrically or circumferentially 4
• Absence of atherosclerotic disease in other vessels 3, 6

Surgical options for CAD (in order of preference):

1. Complete cyst excision without arterial reconstruction if the remaining arterial wall is healthy and solid—this provides better short- and long-term outcomes than arterial reconstruction, particularly important in young patients 7

2. Arterial resection with interposition grafting (saphenous vein preferred over prosthetic) if the arterial wall is compromised or cyst cannot be completely excised 3, 6

3. Percutaneous ultrasound-guided aspiration is an alternative but carries risk of local recurrence 6

If Small Aneurysm (<2.0 cm) Without Thrombus:

Annual ultrasound surveillance is reasonable, though recognize that 31% of small untreated aneurysms eventually require intervention due to symptoms or expansion beyond 2.0 cm. 2, 1, 5 The growth rate averages 1.5 mm/year for aneurysms >2.0 cm versus 0.7 mm/year for smaller ones. 1

Critical Pitfalls to Avoid

• Do not assume atherosclerotic disease in young patients without risk factors presenting with claudication—CAD must be excluded 3, 6
• Do not delay aneurysm repair waiting for symptoms, as outcomes dramatically worsen once thromboembolism occurs 1, 5
• Do not rely solely on CT angiography or standard angiography for CAD diagnosis, as these may underestimate disease severity; intravascular ultrasound (IVUS) provides superior characterization of cystic lesions 4
• Do not miss bilateral disease—always screen the contralateral limb and abdomen 1, 5

When Imaging is Equivocal

If duplex ultrasound cannot definitively characterize the lesions, obtain MR angiography with dynamic plantar flexion maneuvers to define complete popliteal fossa anatomy and evaluate for vascular abnormalities. 8 Consider intravascular ultrasound during angiography if CAD versus aneurysm remains unclear, as IVUS can definitively distinguish extravascular cysts from intraluminal pathology. 4