Overview
This lecture covers the essential steps and key concepts for performing a lower extremity venous ultrasound examination to diagnose deep vein thrombosis (DVT).
Patient Positioning & Preparation
- Position the patient with knee slightly bent and hip externally rotated; support with towel if needed for comfort.
- Start with patient’s right side on the left of the ultrasound screen for orientation.
Anatomy & Initial Scanning
- Begin scanning at the groin crease to visualize the common femoral vein and artery.
- Identify the great saphenous vein (GSV) entry and the branching of femoral vessels.
- Properly label images: non-compressed and compressed views side by side for documentation.
Compression Technique
- Apply gentle pressure to compress the vein; full compression indicates no thrombus.
- Document compressibility at several levels: common femoral, GSV terminus, profunda femoral, upper/mid/distal femoral vein, and popliteal vein.
- Multiple femoral veins may be present; ensure all compress fully.
Doppler & Color Evaluation
- Use spectral Doppler at common femoral and popliteal veins; record augmentation with distal compression and Valsalva maneuver.
- Color Doppler is useful for confirming flow but secondary to compression for DVT diagnosis.
- Adjust Doppler angle, gain, and frequency for optimal signal; document normal phasic flow during respiration.
Scanning the Lower Leg
- Continue compression and documentation down the thigh, through the popliteal region, and into the calf.
- Identify small vessels such as gastrocnemius and peroneal veins; loops can help document small vein compressions.
- Use medial approach for posterior tibial and peroneal vessels; adjust pressure due to depth.
Anterior Tibial Vein
- Anterior tibial vein is rarely included but courses along the anterior-lateral compartment; can be visualized with increased depth.
Exam Completion & Clinical Tips
- Compression from groin to ankle is essential for DVT assessment.
- Keeping patient warm and using adequate gel improves image quality.
- Label and store images or clips showing full compression at all required sites.
Key Terms & Definitions
- DVT (Deep Vein Thrombosis) — blood clot formation in a deep vein, usually of the legs.
- Compression Ultrasound — technique where veins are compressed by the probe; complete collapse excludes DVT at that site.
- Doppler Ultrasound — assesses blood flow direction and velocity using sound waves.
- Phasic Flow — blood flow pattern that varies with respiration, indicating normal venous function.
- Valsalva Maneuver — patient breathes in and bears down to assess vein function on Doppler.
- Great Saphenous Vein (GSV) — major superficial vein of the leg.
Action Items / Next Steps
- Practice documenting compressions at each anatomic level.
- Review and familiarize with venous anatomy on ultrasound images.
- Ensure proper Doppler technique and settings during exams.