What is the workup for bilateral lower extremity discoloration?

Workup for Bilateral Lower Extremity Discoloration

The initial workup for bilateral lower extremity discoloration should include a thorough vascular examination with palpation of lower extremity pulses, auscultation for femoral bruits, inspection of the legs and feet, and measurement of ankle-brachial index (ABI) to evaluate for peripheral artery disease (PAD). 1

Initial Assessment

History

• Assess for exertional leg symptoms:
  • Claudication or walking impairment
  • Fatigue, aching, numbness, or pain in buttock, thigh, calf, or foot
  • Relation of discomfort to rest or exertion
  • Ischemic rest pain
• Evaluate for risk factors of PAD:
  • Age ≥65 years
  • Age 50-64 years with risk factors (diabetes, smoking, hyperlipidemia, hypertension)
  • Known atherosclerotic disease in other vascular beds
  • Family history of PAD 1, 2

Physical Examination

• Measure blood pressure in both arms (to identify subclavian stenosis and establish highest systolic pressure for ABI calculation) 1
• Perform vascular examination:
  • Palpate lower extremity pulses (femoral, popliteal, dorsalis pedis, posterior tibial)
  • Rate pulse intensity (0=absent, 1=diminished, 2=normal, 3=bounding)
  • Auscultate for femoral bruits
  • Inspect legs and feet for:
    • Nonhealing wounds or gangrene
    • Skin color changes (pallor, rubor, cyanosis)
    • Trophic changes (hair loss, nail changes)
    • Temperature differences 1, 2

Diagnostic Testing

First-Line Testing

1. Ankle-Brachial Index (ABI) with segmental pressures and waveforms 1

   • Normal: 1.00-1.40
   • Borderline: 0.91-0.99
   • Abnormal (PAD): ≤0.90
   • Noncompressible vessels: >1.40

2. If ABI >1.40 (noncompressible vessels):

   • Perform Toe-Brachial Index (TBI) with waveforms 1
   • Normal TBI: >0.70
   • Abnormal TBI: ≤0.70

3. If ABI normal (0.91-1.40) but symptoms present:

   • Perform exercise treadmill ABI testing 1

Additional Testing Based on Initial Results

If PAD Confirmed:

• Duplex ultrasound, CT angiography (CTA), or MR angiography (MRA) if:
  • Symptoms are functionally limiting
  • Response to guideline-directed management is inadequate
  • Revascularization is being considered 1

If PAD Not Confirmed:

Consider alternative causes of bilateral lower extremity discoloration:

• Venous insufficiency (assess for edema, varicosities, skin changes)
• Inflammatory conditions (vasculitis, cellulitis)
• Systemic diseases (diabetes, renal disease)
• Medication side effects 3

Special Considerations

For Suspected Critical Limb Ischemia

• In patients with nonhealing wounds or gangrene:
  • Measure TBI with waveforms
  • Consider transcutaneous oxygen pressure (TcPO2) or skin perfusion pressure (SPP) measurements 1

For Suspected Deep Venous Thrombosis

• Bilateral lower extremity ultrasound if symptoms or risk factors for DVT present 4

For Suspected Systemic Disease

• Laboratory testing:
  • Complete blood count
  • Comprehensive metabolic panel
  • Lipid profile
  • HbA1c
  • Consider inflammatory markers (ESR, CRP) if vasculitis suspected 2

Common Pitfalls to Avoid

1. Relying solely on pulse examination - The absence of dorsalis pedis pulse can be normal in some healthy individuals, while absence of posterior tibial pulse is more specific for PAD 1

2. Missing non-atherosclerotic causes - Consider other etiologies such as vasculitis, thromboembolism, or compression syndromes 1

3. Overlooking coexisting disease - Patients with PAD often have coronary artery disease and cerebrovascular disease 1

4. Neglecting ABI measurement in both legs - Bilateral measurements are essential as PAD can be asymmetric 1

5. Failing to screen for AAA - Consider abdominal ultrasound for AAA screening in patients with symptomatic PAD 1

By following this systematic approach, you can effectively evaluate bilateral lower extremity discoloration and determine appropriate management based on the underlying cause.