Superficial. Usually presents as a firm red area over the track of the vein
Usually not a major issue unless it extends towards the groin where the risk of dvt increases
Dvt is an issue as possible pulmonary embolism.
Color changes / pain. Superficial thrombophlebitis can cause some of the changes and symptoms of deep vien thrombosis. Usually on physical exam and a good quality doppler it can be sorted out. Dvt is the dangerous one and travel to lung as a pulmonary embolus. Superficial not life threatening.