Noninvasive diagnosis of deep venous thrombosis.

Deep venous thrombosis of the lower extremity poses a diagnostic challenge. Clinical signs and symptoms are often misleading, and sensitive and specific tests are essential for diagnosis. The cost, patient discomfort and risk of morbidity associated with contrast venography have led to the development of noninvasive diagnostic techniques such as Doppler ultrasound, impedance plethysmography and duplex ultrasound scanning. If noninvasive tests unequivocally indicate deep venous thrombosis, treatment may be started without the need for contrast venography.