Venous reflux

Reflux is a mechanism, not a disease. It describes a flow that heads back in the wrong direction. It is the common starting point of superficial chronic venous disease, and the target that ablation treatments aim at.

The mechanism

In a healthy vein of the lower limbs, blood flows in a single direction, from the bottom up toward the heart. Valves mark out the course and close between two pushes, preventing the blood from flowing back down.

Reflux appears when these valves become incompetent. They no longer close completely, and the blood flows back down under the effect of gravity. This reflux increases the pressure in the downstream segment, contributes to the dilation of the vein, and sustains the venous hypertension at the origin of symptoms and complications.

Measurement on duplex ultrasound

Reflux is demonstrated and quantified by duplex ultrasound, an examination that visualizes the vein and measures the direction and duration of flow. A venous flush is induced, then the duration for which the blood flows back is measured before the valves stop it.

A duration threshold separates physiological reflux, brief, from pathological reflux. This threshold depends on the network considered.

In the superficial network, where varicose veins are seated, reflux is considered pathological beyond 0.5 seconds. This measurement guides the decision to treat and determines the segments to manage.

The target of treatments

Reflux is the mechanism that venous ablation techniques aim at. All of them seek to eliminate the incompetent segment that lets the blood flow back, in order to restore correct drainage through the remaining healthy veins.

The modalities differ by their access route and their agent, thermal or chemical, endovenous or extracorporeal. HIFU treatment targets this same reflux, by closing, from outside the body, the vein that carries it. The mapping of reflux by duplex ultrasound precedes the procedure and defines its path.