Deep vein thrombosis: a perspective on anatomy and venographic analysis.

Pulmonary thromboembolism affects 750,000 Americans annually. DVT is the primary origin of PE, which results in approximately 150,000 patient deaths annually. Normal variants affect the incidence of DVT. Patients with duplicated or fenestrated superficial femoral veins and patients with five or more valves are at increased risk for development of DVT. Positive contrast venography performed in the radiology department under fluoroscopic control remains the "gold standard" for the diagnosis of DVT, despite the development of other modalities. Low-osmolar contrast agents, either nonionic or dilute ionic, and postprocedure infusion of 2,500 U of heparin mixed in 150 mL of physiologic saline should be used to reduce the incidence of postphlebography DVT. Positive venographic signs of DVT include filling defect, cutoff, nonvisualization, and collateralization.