What are the key findings to look for when performing a duplex venous scan of the lower limbs?

From the Guidelines

A duplex venous scan of the lower limbs is a crucial diagnostic tool that reveals several key findings, including blood flow patterns, vein wall thickness, and valve competence, which are essential for diagnosing and managing chronic venous disease, as recommended by the American College of Radiology 1. When performing a duplex venous scan, several key aspects should be evaluated, including:

• Blood flow patterns through the veins, with normal veins displaying spontaneous flow that varies with respiration and increases with distal compression
• Vein wall thickness and compressibility, with healthy veins appearing thin and completely compressible
• Valve competence, with reflux testing used to identify valve dysfunction, where backward flow lasting more than 0.5 seconds indicates valve incompetence 1
• Presence of blood clots (deep vein thrombosis), which appear as echogenic material within the vein lumen, with affected veins showing reduced or absent compressibility
• Venous obstruction, post-thrombotic changes, varicose veins, and anatomical variants, which can be identified using grayscale ultrasound and color/spectral Doppler to assess blood flow direction and velocity 1 The scan should include evaluation of the deep venous system, great saphenous vein (GSV), small saphenous vein (SSV), and accessory saphenous veins, as well as the presence and location of clinically relevant perforating veins and extent of possible alternative refluxing superficial venous pathways 1. The duplex venous scan is a non-invasive and widely accepted imaging technique for assessing the lower extremity venous system, and its findings are essential for guiding treatment decisions and improving patient outcomes 1.

From the Research

Duplex Venous Scan in Lower Limbs

When performing a duplex venous scan in lower limbs, several things are looked for, including:

• Deep venous thrombosis (DVT) 2, 3, 4, 5, 6
• Superficial venous thrombosis (SVT) 2
• Other pathologies such as venous insufficiency or obstruction 2, 3
• The presence of risk factors for DVT, such as previous history of illness, cancer, or recent surgery 3, 5
• The location and extent of the thrombosis, including the involvement of specific veins such as the femoral or popliteal veins 2

Diagnostic Criteria

The diagnosis of DVT is typically made using a combination of clinical assessment, evaluation of pre-test probability, and objective diagnostic testing, including:

• Clinical decision rules to stratify DVT into "unlikely" or "likely" 4
• D-dimer testing to rule out DVT in patients with a low pre-test probability 4, 5
• Compression ultrasound to confirm the presence of DVT 2, 3, 4, 5, 6

Treatment and Management

The treatment and management of DVT typically involves anticoagulation therapy, including:

• Parenteral anticoagulants such as heparin or low molecular weight heparin (LMWH) 4, 5
• Direct oral anticoagulants (DOACs) such as rivaroxaban, apixaban, or edoxaban 4, 5, 6
• Compression therapy to prevent post-thrombotic syndrome 5
• Acute revascularization procedures in rare special cases 5