[Etiology of deep venous thrombosis of the leg].

50% of all patients with deep venous thrombosis (DVT) are simultaneously suffering from other diseases, which might support or cause the thrombogenesis. In the other 50% no etiological factor can be identified. There are several factors predisposing to DVT, such as immobilisation, surgery, old age of the patient, estrogen treatment. These factors are risk factors but not etiological factors. DVT is not only initiated by the three main factors (hypercoagulability, stasis, endothelial lesion) already described by Virchow. A very complicated balance of several complex single systems (endothelium, vessel wall motion, thrombocytes, hemostatic and fibrinolytic systems with their inhibitors) has to be disturbed in order to initiate venous thrombosis.