A vein doctor is a physician trained to diagnose and treat disorders of the veins, such as varicose veins, spider veins, and chronic venous insufficiency. They use non-surgical, minimally invasive techniques like ultrasound-guided sclerotherapy, endovenous ablation, or ClariVein® to improve circulation and relieve discomfort. USA Vein Clinics is a major network of vein treatment centers in the U.S. offering these services at over 160 locations.