What is the need for a follow-up duplex ultrasound (US) in a 71-year-old male with a swollen left foot, positive D-dimer, and initial duplex US showing no deep vein thrombosis (DVT) after recent travel?

Follow-Up Duplex Ultrasound in a Patient with Swollen Foot, Positive D-dimer, and Initial Negative Ultrasound

A follow-up duplex ultrasound is strongly recommended within 5-7 days in this 71-year-old male with a swollen left foot, positive D-dimer, and initial negative ultrasound, especially given the recent travel history which increases DVT risk. 1, 2

Rationale for Follow-up Ultrasound

• Initial negative ultrasound does not definitively exclude DVT when clinical suspicion remains high:

  • Recent travel is a known risk factor for DVT
  • Positive D-dimer indicates active fibrin degradation
  • Persistent symptoms (swollen foot) warrant continued vigilance

• American Society of Hematology (ASH) guidelines specifically recommend:

  • Serial ultrasound when initial ultrasound is negative but clinical suspicion persists 1
  • Follow-up imaging within 5-7 days (or earlier if symptoms worsen) 1

Clinical Algorithm for Follow-up

1. Timing of Follow-up Scan: Schedule repeat duplex ultrasound in 5-7 days 1

   • Earlier follow-up if symptoms worsen
   • Do not wait longer than 7 days as thrombus may propagate

2. Type of Follow-up Ultrasound: Complete Duplex Ultrasound (CDUS) is preferred over limited examination 1

   • Should include compression of deep veins
   • Evaluation of posterior tibial and peroneal veins
   • Spectral Doppler waveforms
   • Color Doppler imaging

3. Expanded Evaluation if Symptoms Persist:

   • Consider iliocaval DVT if whole-leg swelling persists with normal compression ultrasound 2
   • Abnormal spectral Doppler waveforms should prompt pelvic imaging 1
   • CT venography or MR venography may be necessary if iliocaval DVT is suspected 2

Evidence Quality and Considerations

The recommendation for follow-up ultrasound is supported by multiple high-quality guidelines:

• The Society of Radiologists in Ultrasound consensus conference (2018) explicitly states: "A negative ECUS or 2-region test requires a follow-up CDUS in 5 days to 1 week because the calf is not evaluated." 1

• ASH guidelines (2018) note that "suboptimal D-dimer or duplex ultrasound results may require repeat testing" and emphasize that persistent symptoms warrant additional evaluation 1

• Praxis Medical Insights (2025) recommends "repeat scan should be performed in 1 week (or earlier if symptoms worsen)" for suspected DVT cases 2

Important Caveats

• False Negatives: Initial ultrasound may miss DVT, particularly in calf veins or iliocaval segments 1

• D-dimer Limitations: While sensitive, D-dimer has limited specificity and increases with age 3

• Propagation Risk: Studies show that untreated calf DVT can propagate proximally in up to 15% of cases, increasing pulmonary embolism risk 4

• Technical Factors: Suboptimal visualization during initial scan may contribute to false negatives 1

By following this approach, you can ensure appropriate follow-up care for this patient with persistent DVT risk factors despite an initially negative ultrasound.