Inflammation of the wall of a vein. Causes include nearby infection, trauma, surgery, and childbirth. The area over the vein is painful, swollen, red, and hot. A tender, cordlike mass may be felt under the skin. It usually occurs in surface veins in the lower leg and can be treated with pain relievers and bed rest, with mild exercise after inflammation subsides. Phlebitis can last for years; in such cases, irritation of the vein's inner lining leads to blood-clot formation, a condition known as thrombophlebitis (seethrombosis). In deeper veins, this requires anticoagulants to prevent embolisms.