Bedside Ultrasound for DVT. Linear Probe. Leg Veins

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1 Bedside Ultrasound for DVT J. Christian Fox, MD, RDMS, FAAEM, FAIUM Director of Emergency Ultrasound Fellowship University of California, Irvine Linear Probe High frequency transducer 5-10 MHz Superficial structures Superb resolution Leg Veins Paired Superficial and Deep Femoral ARTERIES Deep Femoral Vein NOT seen on ultrasound - caliber too small Common Femoral Vein courses with the paired femoral arteries

2 Leg Veins Paired Superficial and Deep Femoral ARTERIES Deep Femoral Vein NOT seen on ultrasound - caliber too small Common Femoral Vein courses with the paired femoral arteries Femoral Vessels CFV SFA DFA Femoral Vessels CFV SFA DFA

3 Popliteal Veins PV PA Popliteal Vein PV PA

4 Full Compression = No Clot Enough pressure to collapse the vein Excessive pressure when artery is compressed Non-compressibility = DVT Normal veins completely collapse, while DVT prevents venous wall coaptation Failure to wink back = DVT Vein comes to the TOP in the POP Normal veins completely collapse, while DVT prevents venous wall coaptation

5 Vein comes to the TOP in the POP Failure to wink back = DVT Traditional Technique Compression is performed at the level of the inguinal ligament to the bifurcation of the popliteal vein Involves marching all the way through the superficial femoral canal and down through the smaller caliber calf veins This is time consuming How far apart do I space my compressions? It is not necessary to compress every continuous millimeter of the venous lumen searching for a clot In symptomatic patients clot usually involves whole or multiple venous segments Is generally adequate to compress every 1 cm of the femoral and popliteal leg veins

6 Two-point Compression vs Traditional Technique 1. Compression is performed from insertion of great saphenous vein & common femoral vein and distally at least 5cm 2. Compression is performed from proximal popliteal and distal to bifurcation What about Doppler? Duplex term refers to ability to simultaneously perform gray scale imaging with superimposed color flow from structures containing moving RBCs The body of published literature suggests compression ultrasound alone is satisfactory as a diagnostic technique for lower extremity DVT Augmentation Compress a more distal part of the leg A normal vein should fill with color while thrombus appears as a filling defect Suggests patency between the point of compression and the sampling site

7 What about Doppler? Spontaneity Detection of flow in the larger vessels should occur spontaneously without squeezing the calf Phasic Variation Variation of venous flow occurring during the respiratory cycle Increase in Doppler signal during expiration Decrease in Doppler signal during inspiration Pitfalls - Clot Echogenicity Gray scale visualization of the clot would seem to be the most direct method of diagnosis Clot echogenicity is variable and dependent on probe frequency, age of clot, and extent of thrombolytic process Unreliable and not used to diagnose age of clot Slow flowing blood can often appear sufficiently echogenic to mimic the appearance of a clot Sonographic Diagnostic Criteria for DVT Primary Diagnostic Criterion Noncompressibility of a vein Secondary Diagnostic Criterion Echogenic Thrombus Venous Distention Filling Defect Loss of Phasicity Loss of Valsalva Loss of Augmentation

8 Pitfalls - Getting Hung up on Tendon In the popliteal fossa it can be difficult to compress Biceps tendon Muscular groups Pitfalls - Wrong Vein If large patient, make sure you see the paired arterial/venous structures Pitfalls: Bakers Cyst

9 Popliteal vein Pitfalls: Large BMI use C60 Probe Femoral vein Pitfalls: Large BMI use C60 Probe Lymph Node

10 Multiple Inguinal Lymph Nodes Bilateral Femoral Veins Negative for DVT Popliteal DVT

11 Positive DVT Left Femoral Negative Popliteal DVT DVT Conclusions Compress CFV for at least 5 cm distance Compress POP through bifurcation Primary Diagnostic Criterion Noncompressibility of a vein Secondary Diagnostic Criterion Echogenic Thrombus Venous Distention Filling Defect Loss of Phasicity Loss of Valsalva Loss of Augmentation