Ultrasound
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Dx: Multiple Clots Discovered by Ultrasound
 

The images show an abnormal internal jugular (IJ) vein that contains a large amount of clot, which renders the vein non-compressible. The image on the left is without compression and the image on the right is with probe compression. On the left you can see the small superficial external jugular (EJ) vein, which collapses completely during compression on the image on the right. The sternocleidomastoid (SCM) muscle is also shown as is the deeper common carotid (CC) artery. The IJ is not compressible due to clot occupying a large portion of its lumen. The patent part of the lumen is anechoic (black) and the clot is hypoechoic (grey). The lower images are comparison views of the normal right IJ with and without compression. Note how the IJ compresses almost completely when there is no luminal DVT. Because of this, the common carotid (CC) artery is closer to the ultrasound probe at the top of the screen on the right lower image.

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Following review of these images, you order a formal upper extremity venous duplex on the left side, which confirms your diagnosis and shows clot extending all the way to the PICC line in the left arm. The patient is admitted to the medicine service and you let them decide how to anticoagulate her and if and when to remove the PICC line, which is the likely precipitant of the DVT. You then move on to discover what your next trio will be. Maybe a PE, an MI and an aortic dissection in the same shift.  As you have discovered, although things do often come in threes, they may not all have the same final diagnosis!

Tips & Tricks for VENOUS (AND ARTERIAL) THROMBOEMBOLIC DISEASE

01 Probe Choice: Use a high frequency linear array transducer (10-13 MHz).

02 Know your limitations: Ultrasound may help clarify findings elicited by a thorough history and physical exam. When used correctly, it can lead to a more rapid diagnosis and/or improve diagnostic accuracy, especially for critical conditions or unstable patients.  If you use ultrasound in your ED, your department should have a quality improvement program set up that is approved by both ED administration and radiology.

03 Veins: Veins and arteries often run side by side.  You do not want to confuse them.  Veins tend to be thin walled and oval-shaped.  They will collapse with pressure from the ultrasound probe unless they contain a DVT.  In fact, your standard hold of the probe on the skin may be enough to compress the vein and make it non-visible until you let up on the pressure.  A “soft touch” is often required.  Veins should distend with dependent positioning (Trendelenberg) or a Valsalva maneuver. A vein should have non-pulsatile sluggish flow with use of color-Doppler.  Remember, if you cannot see a vein in the expected location, try releasing probe pressure a bit.  

04 Arteries: Arteries tends to be circular rather than oval-shaped, and have thicker walls that are relatively non-compressible.  Use of pulse-wave Doppler should show triphasic flow in an unobstructed artery.  Although anatomic variations may occur, location is also important.  For example, in the groin, the femoral artery is lateral and the femoral vein courses medially. This knowledge however can lead you astray if your probe orientation is reversed. To check orientation, touch the probe with your fingertip while watching the screen.

This should assure that your orientation on the screen is not reversed.  It is standard to have the orientation marker on the left side of the ultrasound screen, and to point the probe indicator marker towards the patient’s right side during the scan.

05 Identifying a clot.  A clot in the vein tends to have a similar echogenicity to the liver, however more acute clots will be relatively darker than more chronic clots.  Also remember that a clot may be non-occlusive, occupying only part of the vessel lumen.  Clots make the vein partially or completely non-compressible.  An arterial clot tends to be more hyperechoic (white) than venous clots.  Since arteries tend to be non-compressible to start with, check for loss of the normal triphasic arterial Doppler signal to confirm.

06 Confirmation: In addition to the steps above, obtain images in multiple planes (longitudinal, transverse, oblique) and utilize the contralateral side for comparison.

07 Augmentation: Squeeze the extremity distal to the site of the suspected clot and watch on ultrasound if there is increased flow under color-Doppler evaluation.  Normal veins should demonstrate good augmentation of flow.  If there is a large, obstructing clot in the vein, augmentation will be diminished.


Brady Pregerson (@TheSafetyDoc) manages a free online EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more info visit EMresource.org.

Teresa S. Wu (@TeresaWuMD) is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa EM Program in Phoenix.

 

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