Sclerotherapy is one method (along with surgery, radiofrequency and laser ablation) for the treatment of spider veins, occasionally varicose veins, and venous malformations. In ultrasound-guided sclerotherapy, ultrasound is used to visualize the underlying vein so the physician can deliver and monitor the injection. Sclerotherapy often takes place under ultrasound guidance after venous abnormalities have been diagnosed with duplex ultrasound. Sclerotherapy under ultrasound guidance and using microfoam sclerosants has been shown to be effective in controlling reflux from the sapheno-femoral and sapheno-popliteal junctions.