In the evaluation of patients with suspected pulmonary embolism (PE), the focus is generally on echocardiography and evidence of right heart strain, but this post covers the frequently neglected utility of lower extremity deep venous thrombosis (DVT) ultrasound.
- It is a quick bedside test that requires little training
- If a proximal DVT is found in a patient suspected of having a PE, then it is very likely that the patient does indeed have a PE1. Therefore, a positive DVT scan can preclude the need for a CTPA, thereby reducing time to treatment, cost of stay, and radiation exposure
- In patients with suspected PE, DVT ultrasound can help guide difficult decisions such as thrombolysis
- It can also be used in cardiac arrest (although there is no data on this) to decide whether to give thrombolysis, as right heart strain can occur in cardiac arrest and not necessarily due to PE– read Jeff Pippin’s post (Dilated RV? Proceed with caution) on this for more information
Convinced? Ok – so how do we do it?
There are lots of different protocols for DVT ultrasound. Let’s talk about how to do extended compression ultrasound.
- Place your linear probe where you would feel a femoral pulse locate the venous saphenofemoral junction. Here you have the common femoral artery, common femoral vein, and saphenous vein creating the classic mickey mouse appearance.
- Compress the vein with your probe. If both venous walls touch and the vein fully collapses, then this excludes a DVT at this point.
- Follow the femoral vein all the way into the popliteal area, compressing at 2cm intervals.
- Finally, at the popliteal level, it is helpful to get the patient to bend their knee (or even prone themselves if possible) so the probe can be placed in the popliteal fossa.
- If you have done this on both legs, then you have excluded most DVT’s (does not rule out iliac vein thrombus)
- Here is a side by side example of a normal popliteal vein and an occlusive popliteal DVT.
- In patients with larger body habitus, using the curvilinear probe may be necessary
- If you are struggling to compress the vein, try pushing the patient’s thigh up towards and against the probe
- A negative DVT study does not exclude a PE!
- Is this test going to alter your management of the patient? if not, probably time to put the probe down
- I’ll say it again, a negative DVT study does not exclude a PE!
- DVT ultrasound can be very useful in patients with suspected PE.
- It can help guide difficult clinical decisions such as thrombolysis, preclude the need for more advanced testing, and allow for more timely initiation of therapeutics.
- So, after you’ve done that echo at the bedside, make sure you have a look at the lower limbs too!
- Roy PM, Colombet I, Durieux P, Chatellier G, Sors H, Meyer G. Systematic review and meta-analysis of strategies for the diagnosis of suspected pulmonary embolism. BMJ. 2005 Jul 30;331(7511):259. doi: 10.1136/bmj.331.7511.259. PMID: 16052017; PMCID: PMC1181264