Venous insufficiency occurs when the one-way valves in the leg veins fail. Venous insufficiency can occur in any of the veins in the leg, from tiny microscopic veins to very large veins in the muscles, fatty tissues, or skin of the legs. The veins enlarge in diameter over a period of years due to a variety of factors such as age, genetics, obesity, pregnancy, injury from previous venous thrombosis (clotting), or venous obstruction.

Early signs of venous insufficiency may include development of spider veins (less than 1 mm in diameter), reticular veins (1-3 mm in diameter), or small varicose veins (over 3 mm in diameter). Other signs include swelling of the ankle at the end of the day, tenderness near the ankle, or pain in the legs with prolonged standing. More severe venous insufficiency may cause enlarging varicose veins, worsening swelling, pain, tenderness, venous stasis skin changes, or venous leg ulcers.

Venous insufficiency is treated after careful diagnostic mapping of the leg veins with reflux testing to determine the location of the leaking one-way valves in the larger veins of the legs. The principles of treatment involve either sealing shut or removing the largest of the abnormal veins. This improves venous outflow in the legs by stopping the venous reflux (the backward venous leak) in the larger veins.

Procedures which may be used to treat venous insufficiency include foam sclerotherapy, endovenous thermal ablation, and microphlebectomy. Compression therapy, usually with support hose, is an important component of managing venous insufficiency and is useful before and after treatment.