What is the appropriate management for an adult patient with unilateral lower limb swelling localized to the ankle, present for 5 days, and potentially having underlying conditions such as hypertension, diabetes, or previous vascular issues?

Management of Unilateral Lower Limb Swelling at the Ankle (5 Days Duration)

The immediate priority is to rule out deep vein thrombosis (DVT) with proximal compression ultrasound or whole-leg ultrasound, as this is the most life-threatening cause of acute unilateral leg swelling and requires urgent anticoagulation to prevent pulmonary embolism. 1

Initial Critical Assessment

Immediate Life-Threatening Conditions to Exclude

• Perform urgent DVT evaluation with compression ultrasound as the first-line diagnostic test, as DVT is the most common vascular cause of acute unilateral leg swelling and can be fatal if untreated 1
• Assess for compartment syndrome or necrotizing soft tissue infection by evaluating for severe pain disproportionate to physical findings, systemic toxicity, or rapid progression—these require immediate surgical consultation 1
• Measure ankle-brachial index (ABI) to determine arterial perfusion status; an ABI <0.6 indicates critical limb ischemia requiring urgent vascular evaluation 2

Key Clinical Features to Document

• Check pedal pulses bilaterally (dorsalis pedis and posterior tibial)—presence of both pulses generally excludes significant peripheral artery disease 2
• Assess for infection signs including erythema, warmth, tenderness, or systemic symptoms (fever, tachycardia), maintaining high suspicion even without pain in patients with diabetes or peripheral artery disease 2
• Evaluate for trauma history, recent surgery, or immobilization as these increase DVT risk 1
• Document cardiovascular risk factors including hypertension, diabetes, smoking, and prior vascular disease 3

Diagnostic Algorithm

Step 1: Vascular Assessment (First 24 Hours)

If DVT suspected (unilateral swelling, calf tenderness, recent immobilization):

• Obtain proximal compression ultrasound or whole-leg ultrasound immediately 1
• Consider iliac vein imaging if extensive unexplained leg swelling without DVT on standard ultrasound 1
• Initiate anticoagulation immediately upon DVT diagnosis without waiting for confirmatory testing if clinical suspicion is high 1

If arterial insufficiency suspected (diminished pulses, cool extremity, pain):

• Measure ABI immediately—values <0.9 indicate peripheral artery disease, <0.6 indicates critical limb ischemia 2
• For ABI <0.6 or ankle pressure <50 mmHg, obtain expedited vascular surgery consultation for potential revascularization 2
• In diabetic patients, also check toe pressures and transcutaneous oxygen pressure (TcPO2) as ABI can be falsely elevated due to arterial calcification 2

Step 2: Infection Evaluation

Maintain extremely high suspicion for infection, especially in diabetic or immunocompromised patients:

• Look for deep-space infection signs including plantar wound with dorsal erythema, fluctuance, or crepitus—these require immediate surgical consultation 1
• Do not rely on fever or leukocytosis to determine infection severity, as these may be absent in severe infections 1
• Initiate empiric broad-spectrum antibiotics immediately covering Gram-positive, Gram-negative, and anaerobic bacteria if infection suspected 1
• If infection coexists with PAD (ABI <0.9), immediate interdisciplinary team referral is necessary as this combination increases amputation risk nearly 3-fold 2

Step 3: Non-Vascular Causes (If Above Excluded)

Consider alternative diagnoses only after excluding DVT, arterial insufficiency, and infection:

• Lymphedema (Stemmer sign positive—inability to pinch skin at base of second toe) 4, 5
• Venous insufficiency (varicose veins, skin changes, history of prior DVT) 5
• Lipedema (bilateral symmetric fat deposition sparing feet, family history, onset at puberty/pregnancy) 6
• Systemic causes (heart failure, renal disease, liver disease, medications)—typically bilateral but can be asymmetric 5

Management Based on Etiology

DVT Confirmed

• Initiate therapeutic anticoagulation immediately with low molecular weight heparin, unfractionated heparin, or direct oral anticoagulant 1
• Transition to long-term anticoagulation (minimum 3 months, potentially lifelong depending on risk factors) 1

Peripheral Artery Disease (ABI 0.6-0.9)

• Aggressive cardiovascular risk reduction: smoking cessation, statin therapy, blood pressure control, diabetes management 2
• Antiplatelet therapy (aspirin or clopidogrel) to reduce cardiovascular events 3
• Consider revascularization consultation, especially for iliac lesions which may benefit from early intervention 3

Critical Limb Ischemia (ABI <0.6)

• Urgent vascular surgery consultation for revascularization evaluation 2
• Initiate unfractionated heparin if acute limb ischemia suspected 3
• Endovascular therapy or surgical bypass depending on lesion characteristics and patient factors 3

Venous or Systemic Causes (ABI ≥0.9, DVT excluded)

• Treat underlying systemic condition (optimize heart failure management, adjust medications) 2
• Graduated compression therapy (20-30 mmHg) for venous insufficiency 2
• Leg elevation when possible to reduce hydrostatic pressure 2

Lymphedema

• Conservative management with compression therapy, manual lymphatic drainage, and skin care 4
• Treat any concurrent cellulitis with antibiotics before initiating compression 4

Critical Pitfalls to Avoid

• Never apply compression without first checking ABI—compression in the setting of significant PAD (ABI <0.5) can precipitate gangrene 2
• Never delay surgical consultation waiting for imaging results if necrotizing infection is suspected—clinical diagnosis takes precedence 1
• Never attribute unilateral swelling to "just venous stasis" without ruling out DVT, PAD, and infection first 2
• Do not use D-dimer alone as a stand-alone test in high pretest probability DVT—proceed directly to ultrasound 1
• Do not be falsely reassured by absence of fever or leukocytosis in diabetic or elderly patients with suspected infection 1

Special Considerations for High-Risk Patients

Diabetic patients:

• Biannual foot examination mandatory even without symptoms 2
• Lower threshold for infection workup and treatment 2
• Check toe pressures if ABI >1.3 (falsely elevated due to arterial calcification) 2

Elderly or immunocompromised patients:

• Lower threshold for infection workup and treatment 2
• More frequent surveillance recommended 2
• Consider broader differential including malignancy-related causes 5