IVC and Iliac Thrombosis

So this is something I think is easy to do but often not taught during education of clinicians who wish to investigate for DVT at the bedside. There is a lot of discussion and literature and controversy over the use of an abbreviated 2 point technique (the femoral vein from saphenofemoral junction to bifurcation, and popliteal vein through trifurcation) vs. a "3 point" technqiue (entire femoral and superficial femoral vein as well as the popliteal vein).

One thing that is not often talked about however is checking for phasicity in the common femoral vein as a marker of proximal venous thrombosis. The idea is that diaphragmatic movement results in changes in intra-thoracic and proximal IVC pressure and will result in increases and decreases in femoral vein flow over the course of the respiratory cycle. The absence of these changes implies that something is blocking the transmission of these pressure changes to the proximal femoral vein. If bilateral femoral veins lack phasicity, thrombus or ocmpression of the IVC is most likely. If unilateral phasicity is absent, iliac thrombosis or compression is most likely on that side.

I've checked for this hundreds of times in patients with leg swelling, but just recently saw my first case of iliac vein thrombosis (where femoral and popliteal exams were completely normal aside from the lack of phasicity). The image above demonstrates normal phasic respiratory flow (on the left side of the pulse wave Doppler tracing), and a flow response to deep breathing (on the right side of the pulse wave Doppler tracing.)

The image above demonstrates absent phasic respiratory flow in the proximal femoral vein on the ipsilateral side of the iliac vein thrombosis. Remember that absent phasicity suggests occlusion of the vein (iliac or IVC) and that this can be due to thrombus or any number of causes of external compression.

References:

Lin EP, Bhatt S, Rubens D, Dogra VS.The importance of monophasic Doppler waveforms in the common femoral vein: a retrospective study. J Ultrasound Med. 2007 Jul;26(7):885-91

Selis JE, Kadakia S. Venous Doppler sonography of the extremities: a window to pathology of the thorax, abdomen, and pelvis. AJR Am J Roentgenol. 2009 Nov;193(5):1446-51.

Willeput R, Rondeux C, De Troyer A. Breathing affects venous return from legs in humans. J Appl Physiol. 1984 Oct;57(4):971-6.