Pulmonary embolism (
PE) is a blockage of the
lung's main artery or one of its branches by a substance that has traveled from elsewhere in the body through the bloodstream (
embolism). PE results from a
deep vein thrombosis (commonly a blood clot in a leg) that breaks off and migrates to the lung, a process termed
venous thromboembolism (VTE). A small proportion of cases are caused by the embolization of
air,
fat, or
talc in drugs of intravenous drug abusers or
amniotic fluid. The risk of PE is increased in various situations, such as
cancer or prolonged
bed rest.