What are the recommended investigations for popliteal artery entrapment syndrome (PAES)?

Recommended Investigations for Popliteal Artery Entrapment Syndrome (PAES)

The optimal diagnostic approach for PAES should begin with ultrasound duplex Doppler as the first-line investigation, followed by MRA for anatomical confirmation, with selective arteriography reserved for confirmatory purposes or pre-surgical planning. 1

Initial Diagnostic Evaluation

Ultrasound Duplex Doppler

• First-line investigation due to its:
  • Non-invasive nature
  • Ability to visualize flow dynamics and vessel caliber in real time
  • Capability to perform dynamic testing with plantar flexion/extension
  • No ionizing radiation exposure 1
• Should be performed both at rest and during active contraction of calf muscles
• Look for:
  • Flow disturbances during plantar flexion
  • Vessel compression or deviation
  • Stenosis, occlusion, or post-stenotic dilation 1, 2

MR Angiography (MRA)

• Recommended as confirmatory test after positive ultrasound findings
• Provides superior evaluation of:
  • Vascular abnormalities
  • Dynamic changes during plantar flexion
  • Abnormal musculotendinous structures
  • Complete anatomy of the popliteal fossa 1
• T1-weighted and T2-weighted sequences are the gold standard for defining complete popliteal fossa anatomy 1
• Should include both neutral position and provocative maneuvers (plantar flexion)

Advanced Imaging

CT Angiography (CTA)

• Alternative when MRA is contraindicated
• Benefits include:
  • Multiplanar reformation and 3D volume-rendered reconstructions
  • Visualization of vessel deviation, stenosis, occlusion, aneurysm formation
  • Identification of abnormal musculotendinous structures 1, 3
• Dynamic CTA with imaging at rest and during plantar flexion can be performed with a single contrast bolus 1
• Less preferred than MRA due to radiation exposure 1

Selective Arteriography

• Traditionally considered the gold standard for identifying:
  • Dynamic arterial deviation
  • Occlusion during plantar flexion
  • Vascular occlusion/stenosis, aneurysm, and thrombosis 1
• Limitations:
  • Invasive procedure
  • Limited ability to depict extravascular anatomy
  • Less specific in determining etiology of symptoms compared to MRI 1
• Best used as a confirmatory modality when PAES is suspected on cross-sectional imaging or ultrasound 1
• Can be combined with intra-arterial thrombolysis in cases with thrombotic complications 1

Emerging Diagnostic Techniques

Intravascular Ultrasound (IVUS)

• Emerging tool for functional PAES diagnosis
• Allows specific localization of compression site
• Particularly useful when other imaging modalities are nondiagnostic 4
• Can assist in operative planning by providing real-time visualization of compression points

Diagnostic Algorithm

1. Initial Screening: Ultrasound duplex Doppler with provocative maneuvers
2. Anatomic Confirmation: MRA with T1/T2 sequences for detailed popliteal fossa anatomy
3. Alternative/Supplemental: CTA if MRA contraindicated or unavailable
4. Pre-surgical Planning: Selective arteriography for confirmation and intervention planning
5. Special Cases: Consider IVUS for functional PAES when other modalities are inconclusive

Clinical Pearls and Pitfalls

• Important Pitfall: PAES is often underdiagnosed due to lack of awareness and can be mistaken for other causes of claudication 5
• Key Consideration: Up to 50% of popliteal artery aneurysms are bilateral, so always examine both limbs 6
• Technical Challenge: During MRA, many patients cannot maintain steady forced plantar flexion throughout lengthy sequences, resulting in motion artifacts and degraded image quality 1
• Clinical Warning: Thrombosis of popliteal arterial aneurysms (a complication of PAES) accounts for approximately 10% of acute arterial occlusions in elderly men and is commonly mistaken for an embolic event 6
• Measurement Criteria: Intraoperative duplex ultrasound showing peak systolic velocities ≥250-275 cm/sec and velocity ratios ≥2.0 may indicate severely injured popliteal arterial segments requiring bypass 7

By following this systematic approach to diagnosis, PAES can be identified early, allowing for appropriate surgical intervention before complications such as thrombosis, stenosis, distal embolism, or aneurysm formation occur.