The aim of this study is to compare 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

Subjects with suspicious iliac vein compression syndrome