The foundation of every vein treatment plan.
You can't treat what you haven't mapped. The visible varicose veins on the surface are the downstream consequence of valve failures higher up — usually in the great saphenous vein or its branches. Without a venous reflux ultrasound, we'd be treating the surface bulges without knowing whether the underlying source is still pumping pressure into them.
The ultrasound traces the flow in every major vein of the leg, both at rest and under provocation (squeezing the calf, standing). When a valve fails, blood briefly flows backward instead of upward — that backward flow is reflux, and the ultrasound measures exactly how severe it is and which veins are affected.
That map is what determines whether EVLT, Varithena, micro-phlebectomy, or some combination is the right approach for you. It's also what insurance requires before authorizing treatment.