Phlebitis may occur with or without a blood clot. It can affect surface or deep veins. When caused by a blood clot, it's called thrombophlebitis. Trauma to the vein, for instance from an IV catheter, is a possible cause.
Symptoms include redness, warmth, and pain in the affected area.
Treatments may include a warm compress, anti-inflammatory medication, compression stockings, and blood thinners.