phlebitis (fləbĪˈtĭs) [key], inflammation of a vein. Phlebitis is almost always accompanied by a blood clot, or thrombus, in the affected vein, a condition known as thrombophlebitis (see thrombosis). Blood-clot formation may follow injury or be associated with infections. Thrombophlebitis of deep veins, usually in the legs or pelvis, may occur in patients recovering from childbirth, surgery, or other conditions requiring prolonged bedrest; the clotting mechanism is thought to be impaired when the legs are immobilized. Pregnancy or the use of oral contraceptives predisposes some women to thrombophlebitis. The major danger is that a clot originating in the leg vein may dislodge and travel to the lung, a condition known as pulmonary embolism (see embolus). To avoid the risk of embolism, thrombophlebitis is usually treated with anticoagulants.