Femoral Vein Doppler Ultrasound Probe Positioning | Lower Limb Veins USG Scanning Technique

Femoral Vein Doppler Ultrasound Probe Positioning | Lower Limb Veins USG Scanning Technique

- Patient Positioning: Have the patient lie supine (on their back) with the leg of interest externally rotated (leg turned outward).
Expose the groin area, ensuring privacy with draping.
- Probe Selection: For most adults, a linear high-frequency probe (often between 7-12 MHz) is ideal. It provides good resolution for superficial structures like the femoral vein.
- Probe Orientation: Start with the probe in the groin crease in a transverse (horizontal) orientation, also known as a short-axis view. This will allow you to view the vessel in cross-section.
- The indicator on the probe should be pointing towards the patient's right side for standard orientation.
- Search for the 'Mickey Mouse sign'. The femoral vein represents Mickey's head, while the femoral artery on the lateral side and the long saphenous vein on the medial side depict his ears. The femoral artery will be seen pulsating. The femoral vein and LSV will compress when probe pressure is applied. The femoral artery is not compressible with probe pressure.
- Press down on the vein using the probe. If the vein fully compresses, there's no thrombus. If there's only partial or no compression, a thrombus is present.
Capture an image without applying compression and another with compression.
- Move the probe down towards the mid thigh in transverse plane.
Apply intermittent compression, for instance, every 1 cm, to check for any thrombus.
- Continue scanning in a Transverse view.
Trace the path of the femoral vein towards the knee, applying compression at intervals.
- As you approach the bottom third of the thigh, the femoral vein moves into the adductor canal. This makes it harder to compress the vein against the femur. To aid compression, use your free hand beneath the leg, pushing upward against the probe.
Capture two images: one without applying compression and another while applying compression.
- Now examine the femoral vein in Longitudinal view. Return to the groin area, identify the femoral vein initially in Transverse view, then rotate the probe 90º clockwise to switch to LS.
Trace the femoral vein all the way down to the knee. Be on the lookout for small non-occlusive thrombi along the vessel wall, particularly near the valves.
- Activate the colour Doppler, and adjust the Pulse Repetition Frequency (PRF: often in the range of 1 to 3 kHz), colour gain (mid-range setting), and wall filter, etc., to enhance edge clarity and prevent colour flow from spilling out of the vein.
Re-scan the femoral vein in LS using colour, inspecting for filling defects, i.e., non-occlusive thrombi. Document any irregularities found (thrombus size, lymph nodes, etc.). Capture one or two illustrative images.