Evidence suggests that patients can be classified as having a high, intermediate, or low probability of having venous thrombosis according to the presence or absence of risk factors, such as recent immobilization, hospitalization within the past 6 months, or malignancy, as well as the clinical manifestations at presentation. Thus, a diagnosis of venous thrombosis can be excluded in patients with a low pretest probability of venous thrombosis and negative findings on noninvasive testing, obviating further testing. A high pretest clinical probability and positive findings on noninvasive testing provide a definitive diagnosis of venous thrombosis. Patients with low pretest probabilities and positive findings on noninvasive testing and those with high pretest probabilities and negative findings on noninvasive testing should undergo venography. Of these, venography and venous ultrasonography are most widely used.
Venography detects both proximal vein and calf vein thrombosis.
For these reasons, this test has been replaced by IPG and venous ultrasonography for the diagnosis of most cases of suspected venous thrombosis. Venous ultrasonography is the noninvasive method of choice for diagnosing venous thrombosis. It is less painful and more convenient to perform than venography. The common femoral vein, superficial femoral vein, popliteal vein, and proximal deep calf veins are compressed with the transducer probe, and the results are observed on the monitor and reproduced in hard copies. Although venous ultrasonography fails to detect a substantial number of calf vein thrombi and small thrombi of the popliteal vein, this limitation is readily overcome.