What is the recommended workup for a 40-year-old male with left calf swelling after a recent long-haul flight?

Workup for Left Calf Swelling After Long-Haul Flight

A complete duplex ultrasound (CDUS) from the inguinal ligament to the ankle is the recommended first-line diagnostic test for this patient with suspected deep vein thrombosis (DVT) after a long-haul flight. 1

Risk Assessment and Initial Evaluation

This 40-year-old male presents with classic risk factors for DVT:

• Recent 11-hour flight (prolonged immobility)
• Unilateral calf swelling

The Wells score should be calculated to assess pretest probability of DVT:

• Recent long-haul flight (+1 point)
• Unilateral calf swelling (+1 point)
• Possibly localized tenderness along deep venous system (+1 point if present)

With at least 2 points, this patient likely has a "DVT likely" pretest probability, warranting immediate imaging rather than D-dimer testing alone.

Recommended Diagnostic Algorithm

1. Complete Duplex Ultrasound (CDUS)

   • Compression ultrasound from common femoral vein to ankle (including posterior tibial and peroneal veins)
   • Color and spectral Doppler of common femoral veins bilaterally
   • Color and spectral Doppler of popliteal vein on symptomatic side
   • Evaluation of symptomatic areas 1

2. If CDUS is not immediately available:

   • Extended compression ultrasound (ECUS) from thigh to knee as a point-of-care test
   • Must be followed by complete duplex ultrasound within 5-7 days if negative 1
   • Consider empiric anticoagulation if CDUS will be significantly delayed

3. If iliocaval DVT is suspected (whole-leg swelling or abnormal spectral Doppler waveforms):

   • Additional pelvic venous imaging with CT venography or MR venography 1

Interpretation of Results

• Positive CDUS: Initiate appropriate anticoagulation therapy
• Negative CDUS: No further imaging needed unless symptoms persist or worsen
• Indeterminate CDUS: Repeat scan in 5-7 days 1

Important Considerations

• Limited ultrasound protocols (not including calf veins) are not recommended as they require a second study in 5-7 days to safely exclude DVT 1
• Long-haul flights of 8+ hours double the risk for calf muscle venous thrombosis, which can extend proximally if untreated 2
• In studies of long-haul travelers, DVT has been found in up to 10% of passengers, with most cases being asymptomatic 3
• This patient's presentation after an 11-hour flight puts him at significant risk, with studies showing a 2.8% incidence of venous thrombotic events after long-haul flights compared to 1.0% in non-travelers 2

Common Pitfalls to Avoid

• Relying solely on clinical examination (unreliable for DVT diagnosis)
• Ordering limited ultrasound protocols that exclude calf veins
• Failing to consider iliocaval DVT if symptoms are severe
• Not providing relevant clinical information to the radiologist (recent flight history)

By following this evidence-based approach with complete duplex ultrasound as the primary diagnostic test, you can accurately diagnose or exclude DVT in this patient with recent travel history and unilateral calf swelling.