Lower Extremity DVT
DVT is a common clinical problem with significant associated mortality from pulmonary embolism. There are approximately 2 million cases per year and nearly 60,000 related deaths per year. DVT can be a difficult disease to diagnose because the signs and symptoms are non-specific and unreliable. Some of the signs and symptoms include calf tenderness, unilateral limb swelling, tachycardia, and tachypnea.


Diagram of the venous drainage of the lower extremity: A-Plantar venous arch; B-Posterior tibial veins; C-Peroneal veins; D-Anterior tibial veins; E-Popliteal vein; F-Femoral vein; G-Deep femoral vein; H-Common femoral vein.

Exam
1-Have the patient âs upper body elevated 10¡-20¡ and examine the leg in external rotation. Do both legs in high risk patients. In low risk symptomatic patients, do the symptomatic leg only. If the Doppler flow is continuous or dampened, sample the contralateral CFV for comparison.
2-In the transverse plane, compress each centimeter of the CFV, SFV and popliteal vein down to the trifurcation. Also identify and compress the central portions of the deep femoral and greater saphenous where these vessels join the CFV. In cases where portions of the deep venous system are poorly visualized in grey scale, longitudinal color images with color filling the vessel can be used to exclude acute DVT. Obtain representative Doppler tracings from the CFV, SFV and popliteal veins. Spontaneous and phasic flow is normal. If the flow is not phasic, assess response to augmentation. If acute thrombus is identified, determine the extent with gentle compression.
3-Calf veins should be examined in patients with anatomic calf pain and a negative femoral-popliteal exam. Follow paired posterior tibilal vein from the medial malleolus proximal. Assess peroneal veins if possible. Greater and lesser saphenous, perforators, calf muscle veins and varicosities may be evaluated if symptomatic. The region of the leg that is tender should be imaged.

Sonographic Findings of DVT:

1) Lack of complete compressibility of vein (beware: a normal femoral vein in adductor canal region may not compress).

2) Visualization of intraluminal thrombus with complete or partial obstruction of the vein lumen.

3) Distention of the vein compared to the adjacent artery

Figure A. Acute thrombus (red arrows) in lower extremity vein is hypoechoic and is commonly indistinguishable from flowing blood. The vein is distended at the site of the acute thrombus (red arrows). Figure B. Inability to compress the vein at the junction of the thrombusis (red arrows) is prime evidence of thrombus.

4) Abnormal venous Doppler signals, i.e. continuous nonphasic flow, reduced or absent flow with distal augmentation, or no obtainable signal.

A

B

A. Longitudinal color Doppler demonstrating normal blood flow in a peripheral vein. B. Longitudinal color Doppler image with transducer compression applied shows flow in the femoral artery (red arrow) and very minimal flow in the femoral vein (red arrowhead). The femoral vein does not compress with transducer pressure, indicating intraluminal thrombus.

5) Continuous, nonphasic flow in CFV unilaterally, with phasic flow in contralateral CFV, suggesting iliac vein outflow obstruction, i.e. DVT of extrinsic compression.



A

B

A. Duplex Doppler demonstrating phasic flow in a normal peripheral vein. B. Duplex Doppler demonstrating non-phasic flow in a peripheral vein with thrombosis



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