1. A method of diagnosing an obstructive lesion in the iliac venous system, comprising the steps of a. non-invasively diagnosing from clinical evaluation alone the presence of chronic venous disease (“CVD”) in a patient, where said clinical evaluation consists of evaluation of one or more of pain, swelling, stasis dermatitis, or venous ulcer and b. performing an intravascular ultrasound (“IVUS”) procedure on said patient's venous system to c. identify any non-thrombotic or thrombotic iliac venous system lesions, d. where said IVUS procedure is performed prior to undertaking other procedures to test said CVD diagnosis where said other procedures consists of one or more of the following: a duplex scan, contrast venography, computed tomography (CT) venography, and magnetic resonance venography.