Venous thromboembolism is a major national health problem, with an overall age- and sex-adjusted incidence of more than 1 per 1,000 annually.1 Because the incidence of this disease is so high and progression from deep vein thrombosis (DVT) to pulmonary embolism (PE) can lead to significant morbidity and mortality, the ability to rule in or rule out DVT in the emergency department is essential.
Explore This IssueACEP News: Vol 28 – No 03 – March 2009
Ultrasound is a sensitive and specific tool for the assessment of patients presenting with symptoms suggestive of lower extremity DVT.2 Focused ultrasound of the lower extremity can be performed quickly by emergency physicians using a simplified three-point compression technique that concentrates on the evaluation of those areas with highest turbulence and at greatest risk for developing thrombus: 1) the common femoral vein at the saphenous junction, 2) the proximal deep and superficial femoral veins, and 3) the popliteal vein.3
Previous research has suggested that the three-point compression technique allows emergency physicians to determine in as few as 4 minutes and with 98% correlation with the radiology-performed complete duplex ultrasound examination the presence or absence of lower extremity DVT.4
A more recent article found that in a heterogeneous group of emergency clinicians, including residents and mid-level emergency providers with different stages in training in ultrasound, the accuracy rate is closer to 85%.5 However, this study also noted that in cases when the clinical gestalt impression of the clinician was that the patient had a high pre-test probability for DVT, the combination with the three-point compression lower extremity ultrasound had a high positive likelihood ratio for DVT.
Emergency physicians should consider performing a three-point compression technique ultrasound of the lower extremity veins in patients presenting with:
- Lower extremity swelling and/or pain.
- Suspected pulmonary embolism, but clinically unstable or with other contraindications to obtaining CT of the chest or VQ scan.
- Pulseless electrical activity (PEA) as part of the assessment for a reversible cause.
How to Perform Ultrasound for DVT
- Patient Positioning: Position the patient as needed to maximize distention of the leg veins. An awake patient may be able to sit on the stretcher with the legs hanging off to the side. However, this manipulation may not be realistic in most instances when dealing with acutely ill patients. Elevating the head of the bed up to a 30-degree to 45-degree angle or positioning the stretcher in reverse Trendelenburg will also allow venous pooling in the lower extremities.6 Flex the patient’s leg at the knee and externally rotate the hip to allow the best exposure of the junction of the common, deep, and superficial femoral veins as well as the popliteal fossa. (See image 1, image 2.)
- Probe Selection: The preferred probe is the high-frequency linear array probe, because it provides better resolution, and its flat surface is ideal for achieving adequate compression. However, larger patients may require the increased penetration of the lower frequency curvilinear probe.
- Probe Positioning: Apply an adequate amount of ultrasound gel on the skin where the probe is located. Hold the probe in transverse position and perpendicular to the skin surface. Start the examination as proximally as possible—ideally at the inguinal ligament. Once the common femoral vein and artery are identified, scan distally until the great saphenous vein emptying into the common femoral vein can be seen. Proceed distally to the junction of the common femoral, superficial femoral, and deep femoral veins. Finally, place the probe in the popliteal fossa for visualization of the popliteal vein and artery.