Should I start with a duplex ultrasound of the veins or arteries to diagnose and manage a patient with symptoms of potential venous or arterial disease?

Duplex Ultrasound for Venous Disease Should Be Performed First in Patients with Suspected Lower Extremity Vascular Disease

For patients with suspected vascular disease of the lower extremities, a complete duplex ultrasound (CDUS) of the venous system should be performed first, as this provides the most comprehensive assessment with minimal risk and can diagnose deep vein thrombosis (DVT) with high accuracy. 1

Diagnostic Approach to Suspected Vascular Disease

Initial Assessment

1. Assess pretest probability for DVT using validated clinical prediction rules:

   • Wells score for DVT (active cancer, paralysis/immobilization, recent surgery, localized tenderness, leg swelling, calf swelling, pitting edema, collateral veins, previous DVT, alternative diagnosis) 1
   • Score ≥2 indicates likely DVT; score <2 indicates unlikely DVT

2. Diagnostic pathway based on pretest probability:

   • Low/unlikely pretest probability: D-dimer testing followed by ultrasound if positive
   • High/likely pretest probability: Proceed directly to ultrasound

Venous Ultrasound Protocol

The Society of Radiologists in Ultrasound consensus recommends:

• Complete duplex ultrasound (CDUS) as the preferred initial test for venous evaluation 1
• Components include:
  • Compression ultrasound from inguinal ligament to ankle
  • Evaluation of posterior tibial and peroneal veins in the calf
  • Right and left common femoral vein spectral Doppler waveforms
  • Popliteal spectral Doppler
  • Color Doppler images

Why Venous Ultrasound First?

1. High diagnostic accuracy: CDUS has high sensitivity and specificity for DVT
2. Safety: No radiation or contrast exposure
3. Comprehensive assessment: Can evaluate the entire venous system from groin to ankle
4. Alternative diagnoses: Can identify other causes of symptoms (12% of studies reveal significant non-thrombotic findings) 2
5. Mortality reduction: Early diagnosis of DVT prevents potentially fatal pulmonary embolism

Arterial Evaluation

Arterial studies should be performed after venous assessment if:

1. Clinical presentation suggests arterial disease (claudication, rest pain, tissue loss)
2. Venous studies are normal but symptoms persist
3. Physical examination findings suggest arterial insufficiency (diminished pulses, pallor, cool extremity)

Important Considerations

Pitfalls to Avoid

• Limited protocols examining only proximal veins are not recommended as they require follow-up studies in 5-7 days 1
• Point-of-care ultrasound without proper training may miss calf DVT
• Bilateral scanning is recommended for inpatients even with unilateral symptoms, as 5% of inpatients have isolated DVT in the asymptomatic leg 3
• Outpatients with unilateral symptoms rarely have isolated DVT in the asymptomatic leg (0% in one study) 3

Special Situations

• Suspected iliocaval DVT: If whole-leg swelling is present with normal compression ultrasound, additional imaging of iliac and pelvic veins is warranted (CT or MR venography) 1
• Recurrent DVT: Can be difficult to distinguish from chronic post-thrombotic changes; look for abnormalities in previously normal vein segments 1

Evidence Quality and Recommendations

The Society of Radiologists in Ultrasound consensus statement provides the strongest evidence for this approach, recommending a single standardized complete duplex ultrasound examination to simplify workup and follow-up 1. This recommendation is based on extensive review of the literature and expert consensus.

The American Society of Hematology guidelines similarly support ultrasound as the primary imaging modality for suspected DVT, with D-dimer testing recommended as an initial step only for patients with low pretest probability 1.

By starting with venous ultrasound, clinicians can effectively diagnose or exclude DVT, which is a common and potentially life-threatening condition, before proceeding to arterial evaluation if necessary.