Complete Duplex Ultrasound (CDUS) from Groin to Ankle
For suspected leg DVT, obtain a complete duplex ultrasound (CDUS) that includes compression of all deep veins from the inguinal ligament to the ankle at 2-cm intervals, plus color and spectral Doppler evaluation—this single comprehensive study is the safest and preferred diagnostic strategy. 1
Essential Components of the Ultrasound
The complete duplex ultrasound must include:
- Compression ultrasound performed at 2-cm intervals from the common femoral vein through the popliteal vein down to the ankle, specifically including the posterior tibial and peroneal veins in the calf 1
- Spectral Doppler waveforms of both the right and left common femoral veins to evaluate symmetry 1
- Spectral Doppler of the popliteal veins 1
- Color Doppler imaging throughout the examination to assess venous filling patterns 1
- Evaluation of symptomatic areas for superficial venous thrombosis or other pathology, particularly if the deep veins appear normal 1
Why Limited Protocols Are Inadequate
Avoid limited protocols that only examine the common femoral and popliteal veins. 1 Here's why this matters clinically:
- Limited examinations miss 30.3% of all DVTs, including isolated superficial femoral vein and calf vein thromboses 2
- Limited protocols require a mandatory second ultrasound in 5-7 days to safely exclude DVT, adding cost, inconvenience, and risk of loss to follow-up 1
- Approximately 15% of untreated calf DVTs propagate proximally, mostly within the first 2 weeks 3
- A single complete study eliminates the need for routine follow-up imaging in most patients 1
When to Order the Ultrasound
First assess pretest probability using the Wells score before ordering any imaging. 1
For Low Pretest Probability (Wells score <2):
- Obtain a high-sensitivity D-dimer first 1
- If D-dimer is negative, no ultrasound is needed—DVT is safely excluded 1
- If D-dimer is positive, proceed to complete duplex ultrasound 1
For High Pretest Probability (Wells score ≥2):
- Proceed directly to complete duplex ultrasound without D-dimer testing 1
For Patients Not Risk-Stratified:
- Complete duplex ultrasound is appropriate 1
Safety of a Single Negative Complete Study
A negative complete duplex ultrasound safely rules out DVT without need for repeat imaging in most patients. 4 The evidence supporting this is strong:
- The risk of venous thromboembolism at 3 months after a negative whole-leg ultrasound is only 0.80% (95% CI 0.16%-2.33%) 4
- No routine follow-up ultrasound is required after a negative complete study unless new or progressive symptoms develop 4
When Repeat Ultrasound IS Mandatory
Despite a negative initial study, repeat imaging within 5-7 days (or sooner) is required if: 3, 5
- Symptoms persist or worsen after the initial negative study 3, 5
- New symptoms of redness, inflammation, or increased swelling develop 3
- The initial study was technically compromised or suboptimal 5
- An isolated calf DVT was found but not treated—repeat in 1 week or sooner if symptoms progress 1, 3
Critical Pitfalls to Avoid
Do not assume bilateral leg examination is always necessary. 6 Ultrasound of the asymptomatic leg is unnecessary in unilateral DVT diagnosis and adds no clinical value 6
Do not miss iliocaval DVT. 3, 5 If the patient has whole-leg swelling but a normal compression ultrasound, this suggests iliocaval disease that standard ultrasound cannot adequately visualize—proceed to CT or MR venography 3, 5
Do not overlook clinically significant non-thrombotic findings. 7 Among positive ultrasound studies requiring immediate treatment, 26% show important findings other than DVT, including pseudoaneurysm, arterial occlusive disease, compartment syndrome, and tumors 7