Sclerotherapy is a procedure used to treat blood vessel malformations (vascular malformations) and also malformations of the lymphatic system. A medicine is injected into the vessels, which makes them shrink. It is used for children and young adults with vascular or lymphatic malformations. In adults, sclerotherapy is often used to treat spider veins, smaller varicose veins, hemorrhoids and hydroceles. 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.  wikipedia.org