Deep Vein Thrombosis (DVT)
Based on this clinical presentation of progressive unilateral leg pain with swelling developing over 3 days in the absence of trauma, the most likely diagnosis is deep vein thrombosis (DVT).
Clinical Reasoning
The patient's presentation follows a classic DVT pattern:
- Progressive unilateral leg pain starting in the anterior shin and extending proximally to involve the entire right lower extremity
- Pain present at rest (a key distinguishing feature from exertional compartment syndromes)
- Development of significant swelling over the shin area with tenderness to palpation
- Inability to ambulate due to pain severity (10/10)
- Absence of trauma, fever, or systemic signs that would suggest infection or other acute processes
Key Distinguishing Features
The temporal progression over 3 days with pain at rest from the onset is critical. This distinguishes DVT from:
- Acute compartment syndrome 1 - which typically follows trauma, crush injury, or reperfusion and presents with the "4 P's" (pain, pain with passive stretch, paresthesia, paresis) requiring urgent fasciotomy within hours
- Chronic exertional compartment syndrome 2, 3 - which presents with reproducible exertional pain that resolves with rest, not pain at rest that progressively worsens
- Soft tissue infection/cellulitis 4 - which would typically show erythema, warmth, and fever
Immediate Next Steps
Obtain urgent lower extremity venous duplex ultrasound to confirm DVT. This is the first-line diagnostic test for suspected DVT.
If DVT is confirmed:
- Initiate anticoagulation immediately (unless contraindicated)
- Assess for pulmonary embolism risk factors and symptoms 5
- Evaluate for underlying thrombophilia or malignancy risk factors
Common Pitfalls to Avoid:
- Do not delay imaging for D-dimer testing in high pretest probability cases
- Do not assume absence of erythema or warmth excludes DVT - these signs are inconsistent
- Do not attribute symptoms to musculoskeletal causes without excluding DVT in patients with progressive unilateral leg swelling and rest pain
The absence of chest pain, dyspnea, or palpitations is reassuring but does not exclude concurrent pulmonary embolism, which should be assessed if DVT is confirmed 5.