Ultrasound for Lower Leg Deep Vein Thrombosis
The standard ultrasound test for diagnosing deep vein thrombosis (DVT) in the lower leg is called Complete Duplex Ultrasound (CDUS). 1
What is Complete Duplex Ultrasound (CDUS)?
Complete Duplex Ultrasound is the preferred diagnostic test for DVT and includes:
- Compression ultrasound of the deep veins from the inguinal ligament to the ankle (including posterior tibial and peroneal veins in the calf)
- Right and left common femoral vein spectral Doppler waveforms (to evaluate symmetry)
- Popliteal spectral Doppler
- Color Doppler imaging
- Compression performed at 2-cm intervals 1
This comprehensive approach provides the highest diagnostic accuracy and is recommended by the Society of Radiologists in Ultrasound Consensus Conference.
Types of Lower Extremity Venous Ultrasound Examinations
Several variations of lower extremity venous ultrasound exist, with different extents of evaluation:
2-CUS (2-region compression ultrasound): Compression ultrasound of the femoral veins 1-2 cm above and below the saphenofemoral junction and the popliteal veins up to the calf veins confluence
ECUS (extended compression ultrasound): Compression ultrasound from common femoral vein through the popliteal vein up to the calf veins confluence
CCUS (complete compression ultrasound): Compression ultrasound from common femoral vein to the ankle
CDUS (complete duplex ultrasound): The most comprehensive test, including compression ultrasound from the common femoral vein to the ankle, plus color and spectral Doppler evaluation 1
Why CDUS is Preferred
CDUS is recommended over limited protocols because:
- It evaluates the entire venous system in one examination
- It eliminates the need for follow-up scans in most cases
- It detects calf DVTs that might be missed by limited examinations
- It provides better data to explain presenting symptoms 1
Limited protocols that don't include calf veins require a second study in 5-7 days to safely exclude DVT, which increases healthcare costs and may lead to missed diagnoses 1.
Point-of-Care Ultrasound Option
When CDUS is not immediately available, a point-of-care ultrasound consisting of extended compression ultrasound (ECUS) from thigh to knee is appropriate as an initial test. However, after a negative ECUS, a follow-up CDUS in 5-7 days is required to safely exclude DVT 1.
Diagnostic Accuracy
The diagnostic accuracy of venous ultrasound is high:
- For proximal compression ultrasound: sensitivity 90.1%, specificity 98.5%
- For whole-leg ultrasound: sensitivity 94.0%, specificity 97.3%
- For serial ultrasound: sensitivity 97.9%, specificity 99.8% 2
Important Clinical Considerations
Follow-up recommendations: If the initial CDUS is negative but symptoms persist or worsen, a repeat scan in 5-7 days is recommended 1
Iliocaval DVT: If iliocaval disease is suspected (e.g., whole-leg swelling with normal compression ultrasound), additional pelvic venous imaging should be considered 1
Incomplete examinations: Incomplete examinations due to patient factors (pain, edema, large leg circumference) should be followed up, as they may miss DVTs 3
Contralateral limb: Consider bilateral examination in patients with risk factors such as age >60 years, malignant disease, or lower extremity trauma, as there's an 18.6% prevalence of contralateral asymptomatic DVT 4
By using the appropriate ultrasound protocol (CDUS) for lower leg DVT diagnosis, clinicians can ensure accurate detection of thrombosis, appropriate treatment, and prevention of complications such as pulmonary embolism and post-thrombotic syndrome.