These risk factors include recent malignancy, major surgical procedures, trauma, prolonged immobilization, pregnancy or use of oral contraceptives, underlying inflammatory states, or a previous history of venous thromboembolism. Before the 1970s, the diagnosis of DVT was made entirely on clinical grounds. With the availability of venography, it became recognized that errors were made when the diagnosis of DVT was based on the clinical examination alone. Venography Ascending venography was the first imaging procedure available for the diagnosis of DVT and has been regarded as the reference-standard technique. Venography remains the only diagnostic test that enables reliable detection of DVT isolated to the calf veins, the iliac veins, or the inferior vena cava.
Venography is also the most accurate method for the diagnosis of asymptomatic thrombi.
However, it has a number of limitations that make it less practical and attractive than noninvasive methods. In addition to the technical challenges associated with obtaining an adequate venogram, there are both minor and serious adverse side effects associated with this invasive procedure. These include local pain, skin reactions, and postinjection superficial phlebitis. Nausea, vomiting, and dizziness may also occur. In the absence of DVT, the entire deep venous system between the common femoral vein and the trifurcation of the popliteal vein should collapse with complete apposition of the vein walls during gentle compression.