If there is an ultrasound confirmation of deep venous thrombosis (DVT) associated with pulmonary symptoms, this may indirectly confirm the diagnosis of PE. Since therapy is often the same for both conditions, further investigation to exclude PE may not be necessary. Prevalence of DVT is 82% in patients with PE. Compression Duplex ultrasound is the primary diagnostic test for DVT in patients having proximal leg symptoms, with a reported sensitivity and specificity of 97 and 94%, respectively. Although the diagnosis of a DVT below the knee is more controversial, reported prevalence of lower limb (infra-popliteal level) DVT is as low as 13% in the patients with proven acute PE. Major restrictions of US imaging limiting its sensitivity in the diagnosis of DVT are the challenging evaluation of calf veins, iliac veins and the inferior vena cava as well as its operator/equipment dependency.