Doppler ultrasound of the veins is a widely used test to search for the presence of deep vein thrombosis (phlebitis) that requires anticoagulation and that may result in pulmonary embolism. This test is often ordered for a patient with signs or symptoms of a suspected pulmonary embolism (pleuritic chest pain, tachypnea, tachycardia, hypocapnia, hypoxia, hypotension) or deep vein thrombosis (leg swelling, calf pain, positive Homan sign) or for a fever workup. Commonly, a preliminary reading that identifies which veins may be harboring clots is placed in the chart or reported verbally by the technician. The decision to anticoagulate a patient hinges on these results. In this setting, it is important to know the venous anatomy of the leg and the risk of pulmonary embolism for phlebitis of the relevant veins.