LEG VEINS
DVT: compression ultrasound
When to use it
- Check for a deep vein thrombosis before surgery in a patient with a swollen leg, for example after a fracture or long immobility.
- Look for a source of clot when pulmonary embolism is suspected during or after surgery.
- Probe
- Linear, high frequency
- Position
- Supine, 10–30° head up, leg turned out, knee slightly bent
- Depth
- 3–5 cm (deeper in large legs)
How to scan
- Point 1, groin: probe across the thigh at the inguinal crease. Find the common femoral artery and the vein medial to it, where the great saphenous vein joins.
- Press down gently until the artery just starts to change shape. A normal vein closes completely. Repeat every 1–2 cm, down to where the femoral vein splits.
- Point 2, behind the knee: patient on the side or knee bent. Find the popliteal vein (above the artery on the screen) and compress it down to where the calf veins branch off.
- A three-point scan adds the femoral vein in the mid-thigh.
Transverse view at the groin. Left: the vein (larger, medial) and artery. Right: gentle pressure closes a normal vein completely.
- CFA
- common femoral artery: round, pulsatile, does not squash
- CFV
- common femoral vein: larger, medial to the artery
- Pressing
- gentle pressure closes a normal vein completely. A vein that will not close, or has grey material inside, means DVT
Original schematic illustration © Nerve Blocks. Not to scale.
What you see and what it means
| On the screen | What it means |
|---|---|
| Vein closes completely | No DVT at that point |
| Vein doesn't close, even when the artery is squashed | DVT |
| Grey material inside a distended vein | Clot (fresh clot can be almost black) |
Pearls
- Two-point compression doesn't look at the calf veins. If the scan is normal but DVT is still likely, arrange a formal scan or repeat in about a week.
- Press just enough to close a normal vein, and stop when you see clot: no need to keep pressing.
- A lymph node or a Baker's cyst can look like a vein: follow it up and down.
References
- Lee JH, Lee SH, Yun SJ. Comparison of 2-point and 3-point point-of-care ultrasound techniques for deep vein thrombosis at the emergency department: a meta-analysis. Medicine (Baltimore) 2019;98:e15791. PubMed
