Venous Reflux is what causes varicose veins and symptoms of venous insufficiency such as swelling. Veins carry blood towards the heart from the legs. When valves become floppy and non-functional, gravity pulls the blood towards the feet in the wrong direction. Abnormal valves and the resultant “reflux” can be detected with an ultrasound. This lets the vein specialist know what treatment to recommend. An ultrasound exam done by an experienced examiner is advised before any varicose vein procedure and in a patient with leg pain or swelling.