Vascular Ultrasound Versus Intravascular Ultrasound for Diagnosing Iliac Vein Obstruction

Inclusion Criteria: * Advanced Chronic Venous Insufficiency (CEAP 3-6) submitted to clinical treatment for at least 1 year with no response. * Subject must be \> 18 and \< 80 years of age * Willing to participate in and able to understand, read and sign the informed consent document before the planned procedure * On duplex ultrasound: patent common femoral vein, and patent deep femoral vein, and/or femoral vein of the study leg Exclusion Criteria: * Subject cannot or will not provide written informed consent * Previous venous stent implantation involving the study leg or inferior vena cava * Previous venovenous bypass surgery involving the study leg * Known reaction or sensitivity to iodinated contrast that cannot be managed with premedication * Subjects who are pregnant (women of childbearing potential must have a negative pregnancy test within 7 days prior to enrollment * Acute deep venous thrombosis involving either leg * Known history of chronic total occlusion of the common femoral vein of the study leg. * Known history of thrombophilia (e.g., protein C or S deficiency, anti-thrombin III deficiency, presence of lupus anticoagulant, etc.) * Venous compression caused by tumor encasement * Venous outflow obstruction caused by tumor thrombus * Life expectancy of less than 6 months * Lower Extremity Arterial Insufficiency * Elevated baseline blood creatinine (value greater than the upper limit of the normal range) * Any concurrent disease or condition that, in the opinion …