Venous hypertension causes leg swelling, throbbing, and capillary breakdown with extravasation of blood into the surrounding tissues.  Here the blood cells lyse releasing the components to be reabsorbed by the body.  However the iron in hemoglobin is not resorbed and is deposited in the tissues causing brownish discoloration(hemosiderin deposition) and results in tissue fibrosis an poor wound healing.  There are 2 venous systems in the legs, the superficial system involving the greater saphenous vein and varicose veins that are just under the surface, and the deep venous system which are veins that course with the arteries.  Deep venous thrombosis results in deep venous occlusions that permanently injure the valves resulting in reflux of the blood(blood going toward the foot instead of back to the heart ).  Greater saphenous vein reflux is caused by damaged valves, therefore the blood does not continue flowing to the heart and pools in the lower leg.  A venous ultrasound with reflux study identifies the refluxing veins. 

In the deep system, while there can be some recanalization over time, the valves are damaged preventing the normal flow back to the heart and compression therapy is the main treatment option.  If the greater saphenous vein is refluxing, and the deep system is normal, fibrosing this vein will allow the blood to be redirected to the deep system and progress out of the extremity.  Thermal ablation therapy using laser or radiofrequency fibroses the greater saphenous vein to obliterate it, but requires extensive anesthetic infiltration to narrow the vein and protect the surrounding tissue from thermal injury.  I use a catheter(clarivein) to abrade the inner vein lining mechanically causing the vein to constrict and then use a small amount of sclerosant to fibrose the vein without the need for extensive tumescent injection.  After the major refluxing vein is obliterated, therapy as directed to the medium  sized varicose veins usually with stab phlebectomy's(small incisions to remove the veins) and the small varicose veins using sclerotherapy.