A duplex ultrasound is two ultrasounds in one pass: the familiar grey-scale picture of the vein's structure, plus Doppler, which colours in the direction and speed of blood flow. That combination is exactly what vein disease requires — the whole question is whether blood flows the wrong way, and duplex shows it happening live.
It's painless, radiation-free, and the standard first test for leg veins and often pelvic veins. Two details determine its quality:
- Position. Valves leak under gravity, so leg studies should be done standing (or steeply tilted). A lying-down vein exam can miss the reflux entirely — one of the main reasons for "normal" scans in symptomatic women.
- Provocation. For pelvic veins, manoeuvres like bearing down (Valsalva) make hidden reflux show itself.
It's also operator-dependent — a sonographer who knows to hunt reflux finds things a routine abdominal scan won't. Where duplex sits in the full testing sequence: how PeVD is diagnosed.