Comparison of Intravascular Ultrasound With Venography in the Diagnosis and Treatment of Iliac Vein Compression Syndrome

Inclusion Criteria: * Age: 18 to 90 years * Willing to participate in and sign the informed consent * Patients with suspicious iliac vein stenosis or compression presented by preoperative magnetic resonance venography (MRV) * Patent common femoral vein and/or femoral vein of the study leg * Undergoing iliofemoral venography with the intend to treat potential iliac vein compression syndrome Exclusion Criteria: * Not providing informed consent * Venous compression caused by pelvic tumors or fibroid uterus * Previous stent implantation or venovenous bypass surgery of the study leg * Known metal allergy precluding the possibility of stent implantation * Known iodine allergy or severe renal insufficient function which are unsuitable for venography * Pregnant or planning to be pregnant recently * Acute deep vein thrombosis or tumor thrombus involving the study leg * Know history of thrombophilia (e.g. protein C or S deficiency, anti-thrombin III deficiency, etc ) * Any concurrent disease, for example, heart failure, might make the patients unsuitable for surgery