Spider veins are fine, under the skin surface, visible blood vessels. They occur mainly on the legs, and are formed when underlying venous valves are leaking and cannot pump the blood towards the heart. Spider veins are often the first indication of disease in the deep vein system. Therefore entire superficial vein system and deep vein system should always be examined before treatment to diagnose if there is a varicose vein or any another form of chronic venous insufficiency (CVI).
One possible cause of a superficial phlebitis (Medical: superficial thrombophlebitis) may be the formation of a blood clot (thrombus). Signs of phlebitis are a significant redness, swelling, heat or pain along the vein.