In thrombophlebitis, in which the veins are inflamed, swollen, and tender, the affected veins can be seen as red tracks.
Thrombophlebitis is inflammation of a section of vein, usually just under the skin, with clot formation in the affected part. This can occur after minor injury to the vein or as a complication of varicose veins or Buerger's disease. The affected blood vessel is swollen, red, and tender, and feels hard. Fever and malaise may occur. A blood clot may develop.