What is the workup for lower extremity edema?

Workup for Lower Extremity Edema

The workup for lower extremity edema should begin with determining chronicity and laterality of edema, followed by basic laboratory tests (basic metabolic panel, liver function tests, thyroid function, BNP, urine protein/creatinine ratio), and appropriate imaging based on suspected etiology. 1

Initial Assessment

History

• Duration: Acute vs. chronic
• Laterality: Unilateral vs. bilateral
• Associated symptoms:
  • Pain, claudication, rest pain
  • Shortness of breath
  • Recent travel or immobility
• Medication review: Antihypertensives, NSAIDs, hormones 1
• Risk factors for PAD: Age ≥65 years, smoking, diabetes, hyperlipidemia, hypertension 2

Physical Examination

• Inspect legs and feet for:
  • Color changes, warmth, or erythema
  • Trophic skin changes (hair loss, skin thickening)
  • Ulcerations or wounds
  • Varicose veins
• Palpate:
  • Lower extremity pulses (dorsalis pedis, posterior tibial, popliteal, femoral)
  • Character of edema (pitting vs. non-pitting)
  • Tenderness
• Auscultate for femoral bruits 3, 2

Laboratory Testing

• Basic metabolic panel
• Liver function tests
• Thyroid function tests
• Brain natriuretic peptide (BNP)
• Urine protein/creatinine ratio
• D-dimer (if DVT suspected) 1, 4

Diagnostic Algorithm Based on Presentation

Acute Unilateral Edema

1. Immediate evaluation for DVT:
   • D-dimer testing
   • Compression ultrasonography 1
   • If clinical suspicion remains high despite negative ultrasound, consider MR venography to rule out pelvic or thigh proximal venous thrombosis 4

Chronic Bilateral Edema

1. Systemic causes assessment:

   • If elevated BNP or signs of pulmonary edema → Echocardiography for heart failure evaluation
   • Abnormal liver function tests → Further hepatic workup
   • Abnormal renal function → Nephrotic syndrome evaluation
   • Abnormal thyroid function → Appropriate thyroid management

2. Vascular assessment:

   • Ankle-Brachial Index (ABI) measurement
     • Normal: 1.00-1.40
     • Borderline: 0.91-0.99
     • Abnormal (PAD): ≤0.90
     • Noncompressible: >1.40 (requires Toe-Brachial Index) 3, 2
   • Duplex ultrasonography with reflux study for chronic venous insufficiency 1

3. Sleep apnea consideration:

   • STOP-Bang questionnaire if obstructive sleep apnea suspected 1

Chronic Unilateral Edema

1. Lymphedema assessment:

   • Clinical diagnosis based on brawny, non-pitting edema
   • Consider lymphoscintigraphy if diagnosis unclear 1, 4
   • Evaluate for secondary causes: malignancy, prior surgery, radiation, trauma

2. Lipedema consideration:

   • Evaluate for disproportionate fat deposition 5

Specialized Testing When Indicated

• Duplex ultrasound: For anatomic location and degree of stenosis in PAD 2
• CT angiography with runoff: For suspected vascular etiology requiring detailed anatomical information
• MR angiography with runoff: Alternative to CTA, especially with renal insufficiency
• Pulse volume recordings/plethysmography: For further vascular evaluation 2
• Exercise ABI: When resting ABI normal but clinical suspicion for PAD remains high 2

Common Pitfalls to Avoid

1. Failing to consider medication-induced edema
2. Missing DVT in patients with minimal symptoms
3. Overlooking systemic causes in bilateral edema
4. Assuming all unilateral edema is vascular in origin
5. Not recognizing noncompressible vessels (ABI >1.40) in diabetic or elderly patients, which require TBI instead 2
6. Treating with diuretics without identifying the underlying cause

By following this systematic approach to lower extremity edema evaluation, clinicians can efficiently diagnose the underlying cause and implement appropriate management strategies.