Acute Unilateral Leg Swelling After Fall: Diagnostic and Management Approach

Immediate Life-Threatening Assessment

The first priority is to rule out acute limb ischemia (ALI), which represents a vascular emergency requiring intervention within 4-6 hours to prevent permanent tissue damage and limb loss. 1

Critical "6 Ps" Bedside Evaluation

Immediately assess for the six classic signs of acute limb ischemia 1:

Pain – Sudden, severe leg pain
Pallor – White or mottled skin appearance 1
Pulselessness – Absent femoral, popliteal, dorsalis pedis, or posterior tibial pulses 1
Poikilothermia – Cold limb compared to contralateral side 1
Paresthesia – New sensory loss distal to the lesion 1
Paralysis – Motor weakness or inability to move the limb 1

Use a handheld Doppler immediately at the bedside to assess arterial signals at the dorsalis pedis and posterior tibial arteries. Loss of arterial signal indicates a threatened limb requiring emergent intervention. 1

If ANY Sign of Acute Limb Ischemia is Present:

Start unfractionated heparin immediately without waiting for imaging 1
Obtain emergent vascular surgery consultation before imaging is completed 1
Proceed directly to CT angiography (CTA) of the entire lower extremity as the preferred rapid diagnostic test 1
If motor weakness or paralysis is present (Rutherford Category IIb or III), proceed directly to the operating room or catheter suite without imaging to avoid treatment delays 1

Deep Vein Thrombosis (DVT) Evaluation

If arterial pulses are present and the limb is warm, the most likely diagnosis is deep vein thrombosis, which is the leading cause of acute unilateral leg swelling after trauma. 2

Immediate Diagnostic Steps:

Obtain compression duplex ultrasound of the entire affected leg from the common femoral vein to the calf veins as the first-line diagnostic test 2
Duplex ultrasound is portable, readily available in emergency departments, and can rapidly confirm or exclude DVT 2

Clinical Risk Factors Supporting DVT:

The combination of trauma (fall), immobility, and chronic venous changes (discoloration, chronic edema) significantly increases DVT risk 2. The presence of 2+ pitting edema extending from hip to foot suggests extensive venous obstruction 2.

Compartment Syndrome Consideration

Compartment syndrome must be excluded in any patient with acute leg swelling after trauma, especially if pain is disproportionate to physical findings. 2

Red Flags for Compartment Syndrome:

Severe pain disproportionate to examination findings 2
Pain with passive stretch of muscles in the affected compartment 2
Tense, swollen compartments on palpation 2
Progressive sensory deficits 2
Motor weakness developing over hours 2

If compartment syndrome is suspected clinically, proceed immediately to surgical consultation for compartment pressure measurement and potential fasciotomy. Do not delay for imaging. 2

Fracture and Musculoskeletal Injury Assessment

Imaging Protocol:

Obtain plain radiographs (AP and lateral views) of the entire leg from hip to ankle as the initial imaging study to exclude fracture, especially given the mechanism of fall 3. Weight-bearing films are not appropriate in this acute setting with significant swelling 3.

Special Considerations:

Hip fractures in elderly patients may present with leg swelling and discoloration due to soft tissue hemorrhage 3
Occult fractures may not be visible on initial radiographs; if clinical suspicion remains high despite negative X-rays and DVT is excluded, obtain MRI without contrast 3

Chronic Venous Insufficiency with Acute Decompensation

The chronic discoloration and dryness suggest underlying chronic venous insufficiency, which may have acutely worsened after the fall 2. However, this diagnosis can only be made after excluding acute limb-threatening conditions (ALI, DVT, compartment syndrome, fracture). 2

Structured Diagnostic Algorithm

Step 1: Immediate Bedside Assessment (Within Minutes)

Check all six "Ps" of acute limb ischemia 1
Palpate pulses bilaterally; use handheld Doppler if pulses not palpable 1
Assess compartments for tension and pain with passive stretch 2

Step 2: If Arterial Pulses Absent or Doppler Signals Lost

Start IV heparin immediately 1
Call vascular surgery emergently 1
Obtain CTA lower extremity (unless Category IIb/III, then go directly to OR) 1

Step 3: If Arterial Pulses Present and Compartments Soft

Obtain compression duplex ultrasound to evaluate for DVT 2
Obtain plain radiographs (AP/lateral) of entire leg to exclude fracture 3

Step 4: If DVT Confirmed

Start therapeutic anticoagulation 2
Elevate leg above heart level 4
Apply compression as tolerated 4

Step 5: If DVT and Fracture Excluded

Consider chronic venous insufficiency with acute exacerbation 2
Evaluate for soft tissue injury, hematoma, or cellulitis 2
If concern for occult fracture persists, obtain MRI 3

Common Pitfalls to Avoid

Do not assume chronic venous changes explain acute swelling – Always exclude acute limb-threatening conditions first 2
Do not delay anticoagulation or vascular consultation while awaiting imaging if acute limb ischemia is suspected 1
Do not rely on palpable pulses alone in high-risk patients (diabetes, elderly, prior vascular disease) – obtain objective ABI or Doppler assessment 1
Do not order ABI as the primary investigation for acute limb ischemia – it confirms occlusion but provides no anatomic information for revascularization planning 1
Do not miss compartment syndrome – if clinical suspicion exists, proceed directly to surgical evaluation without imaging delays 2

Risk Factors Increasing Urgency

Age ≥70 years or ≥50 years with smoking or diabetes 1
History of peripheral artery disease or prior claudication 1
Atrial fibrillation or recent myocardial infarction (embolic source) 1
Chronic kidney disease 2
Prolonged immobility after fall 2

What is the appropriate evaluation and management for acute unilateral leg swelling from the hip to the foot after a fall, with chronic discoloration, dryness, and mild chronic edema?

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