Swelling and irritation of a vein due to a blood clot, often in the legs.

Thrombophlebitis is swelling and irritation of surface or deep veins due to a blood clot. The blood clot can change or block blood flow. Thrombophlebitis usually affects the legs. It can be deadly if the clot moves to a lung. Causes include injury, surgery or not being active for a long time.

Symptoms include warmth, pain, and swelling. The skin may look red, depending on skin color.

Treatments may include blood-thinning medicines, compression stockings, and surgery.