 Whether isolated distal DVT IDDVT, DVT confined to the calf, should be looked for and diagnosed to allow them to be treated with anticoagulants remains one of the still unsolved issues in vascular medicine, especially because of the insufficient data on clinical risks of untreated distal DVT. Management studies have shown that it is safe to withhold anticoagulation in outpatients with suspected DVT if compression ultrasonography CUS limited to the proximal deep veins yields normal results on presentation and on repeated examination after 5 to 7 days. This strategy is based on the premise that IDDVT do not need to be diagnosed and treated, what is necessary when they extend involving the proximal veins. There is no general agreement, however, on the assumption that the non-extending IDDVT do not need to be diagnosed and treated, and many authors recommend to perform a single CUS examination extended to the distal deep veins. All the available studies have treated with anticoagulants the diagnosed IDDVT and no adequate information is available on the risk of IDDVT left untreated. 