The most common cause of pulmonary embolism is
About half of the patient with pelvic vein thrombosis or proximal leg deep vein thrombosis have pulmonary thromboembolism. Isolated calf vein thrombosis pose a lower risk of pulmonary embolism. The majority of pulmonary emboli arise from the propagation of lower limb deep vein thrombosis (p. 186). Rare causes include septic emboli (from endocarditis affecting the tricuspid or pulmonary valves), tumour (especially choriocarcinoma), fat following fracture of long bones such as the femur, air, and amniotic fluid, which may enter the mother's circulation following delivery. Ref Davidson edition23rd pg 620
Amniotic fluid embolism
Calf vein thrombi
Pelvic vein thrombosis
Cardio thoracic surgery
Respiratory system