Venogram vs. Intravascular Ultrasound (IVUS) for Diagnosing Iliac Vein Obstruction

Inclusion Criteria: * Subject must be \> 18 and \< 85 years of age * Willing to participate in and able to understand, read and sign the informed consent document before the planned procedure * CEAP clinical classification: C4, C5, or C6 (enrollment of C4 and C5 subjects will be capped at 50, such that at least 50 C6 subjects can be enrolled) * On duplex ultrasound: patent common femoral vein, and patent deep femoral vein, and/or femoral vein of the study leg * Undergoing iliofemoral and inferior vena caval venography with the intent to treat obstructive lesions 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 metal allergy precluding endovascular stent implantation * 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 * Severe, untreated (and readily treatable) superficial venous reflux (great saphenous vein \>7 mm in diameter, and/or small saphenous vein \>4 mm in diameter) * 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 l…