A commonly performed non-surgical treatment for varicose and "spider" leg veins is sclerotherapy. It has been used in the treatment of varicose veins for over 150 years. Sclerotherapy is often used for telangiectasias (spider veins) and varicose veins that persist or recur after vein stripping. Sclerotherapy can also be performed using microfoam sclerosants under ultrasound guidance to treat larger varicose veins, including the greater and short saphenous veins. A study by Kanter and Thibault in 1996 reported a 76% success rate at 24 months in treating saphenofemoral junction and great saphenous vein incompetence with STS 3% solution. A Cochrane Collaboration review concluded sclerotherapy was better than surgery in the short term (1 year) for its treatment success, complication rate and cost, but surgery was better after 5 years, although the research is weak. A Health Technology Assessment found that sclerotherapy provided less benefit than surgery, but is likely to provide a small benefit in varicose veins without reflux. Complications of sclerotherapy are rare but can include blood clots and ulceration. Anaphylactic reactions are "extraordinarily rare but can be life-threatening," and doctors should have resuscitation equipment ready. There has been one reported case of stroke after ultrasound guided sclerotherapy when an unusually large dose of sclerosant foam was injected.

From http://en.wikipedia.org/wiki/Varicose_veins#Sclerotherapy