Lower Extremity Venous Ultrasound Guide

Overview

This lecture provides a step-by-step guide for performing lower extremity venous ultrasound exams focused on detecting deep venous thrombosis (DVT), including proper technique, common pitfalls, and practical tips to avoid false positives.

Indications and Key Concepts

• Lower extremity venous ultrasound is primarily used to assess for DVT in patients with symptoms like calf pain, swelling, tenderness, and warmth.
• The exam's main goal is to confirm the presence or absence of a blood clot.
• Accurate exams rely on a thorough understanding of anatomy, correct compression technique, and using arteries as anatomical guides.

Protocol and Technique

• Position the patient supine with the knee slightly bent (frog leg) for optimal access.
• Begin with locating the common femoral vein, which is medial to the femoral artery, using a linear probe in transverse orientation.
• Identify veins by their thinner walls and compressibility; arteries are thicker-walled and pulsatile.
• Proper compressions are crucial: start above the saphenofemoral junction and progress down the leg, compressing every few centimeters.
• After transverse imaging, switch to longitudinal views for 2D, color Doppler, and spectral Doppler assessment.
• Use color Doppler with a slight probe angle to maximize vessel fill; spectral Doppler should show spontaneous and phasic blood flow.
• Augment flow by distal compression (squeezing the leg) to demonstrate venous patency.

Imaging Sequence and Tips

• Image the common femoral, proximal femoral, deep femoral, mid femoral, distal femoral, popliteal, gastrocnemius, posterior tibial, and peroneal veins sequentially.
• If veins are hard to locate, follow adjacent arteries or return to a known anatomical landmark and trace distally.
• For challenging compressions, use the back of the hand or apply pressure behind the leg to improve patient comfort.
• Adjust probe type (curved vs. linear) for larger limbs as necessary.
• Always compress all veins visualized, and use color Doppler and augmentation to confirm vein patency.

Common Pitfalls and How to Avoid Them

• Do not mistake sluggish or rouleau flow for DVT; true DVT prevents vein compression, while rouleau flow veins still fully compress.
• Incomplete vein compression may occur if the patient is holding their breath or tensing up; coach the patient to relax and exhale during compressions.
• Difficulty filling veins with color Doppler often results from shallow breathing or apnea; prompt deep breaths and capture images on exhalation.
• For consistent image orientation, confirm probe position (the great saphenous vein branches medially, with side varying by leg).

Tips and Tricks

• Use arteries as anatomical guides, especially if veins are hard to see.
• Employ color Doppler and augmentation to differentiate veins from arteries and confirm flow.
• For calf veins, scan in transverse and use color Doppler and artery location to assist identification.
• Adjust imaging for vessel depth and patient body habitus as needed.

Recommendations / Advice

• Always start at a known anatomical landmark and proceed methodically to avoid missing pathology.
• Use proper compression at each segment and verify with Doppler and augmentation techniques.
• Coach patients for optimal relaxation and breathing to improve exam accuracy and comfort.