Case #9: Leg pain

HPI: 44yo female without PMH presents to the ED from her primary doctor's office with a chief complaint of "left lower extremity swelling." The patient had noted increased swelling and discoloration to her entire left leg over the past several days. She has no risk factors for blood clots.

Physical Exam:

Extremities: Unremarkable bilateral upper extremities and right lower extremity. Left lower extremity reveals a swollen leg with 1+ pitting edema extending to the proximal thigh; leg is painful to the touch with a "milk white" appearance consistent with phlegmasia alba dolens; 1+ DP pulse with delayed cap refill

Bedside Ultrasound:

What is abnormal about this ultrasound?

What structures do you see?

Under compression, the vein does not completely compress. Actually it doesn't compress at all!

Diagnosis:

DVT found to be a result of May-Thurner Syndrome

May-Thurner Syndrome (MTS), also known as Iliac Vein Compression Syndrome, occurs when the common iliac vein is compressed because of the overlying common iliac artery. This is typically compression of the left common iliac vein caused by the right common iliac artery. As the aorta descends along the left lateral side of the inferior vena cava, its terminal branch will cross on top of (and sometimes compress) the left terminal branch of the IVC against the lumbar spine. This compression can lead to discomfort, decreased venous return, and ultimately deep venous thrombosis. As the DVT initiates at a proximal location in the lower extremity, the thrombus can be very large and propagate quickly.

Ultrasound Education:

Lower extremity venous compression via ultrasound is compression of the venous system at 1cm increments to evaluate for DVT. A linear probe is used in this process.

Starting at the proximal thigh within the groin, the vein is compressed by pressing the probe into the skin surface at a 90 degree angle and noting the collapsing of the vein under external pressure. Arteries near to the vein will most likely not compress. Arteries are thick-walled, pulsatile and "bouncing" in comparison to the thin-walled easily collapsible veins. The bedside ultrasonographer will start the exam at the point where the Greater Saphenous Vein (GSV) of the superficial venous system meets with Common Femoral Vein (CFV) of the deep venous system. The EM provider then tracks the vein distally through the Femoral Vein, and finally moves the probe to the posterior aspect of the knee to evaluate the Popliteal Vein.

During compression with the probe, the anterior and posterior walls must touch for the vein to be called completely compressible. If they do not touch during compression with the probe, there is concern for a thrombus at that location. Following each vein as distally as possible until no longer able to discern the vein ensures evaluation of the entire deep venous system via ultrasound.

Additional resources:

1. http://www.emdocs.net/case-rare-cause-dvt-young-healthy-patient/ -a great review on May-Thurner written by an expert in the field ;)

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3377287

-Bristol Schmitz MD