Definition of Pulmonary embolus:

A pulmonary embolus is a blockage of an artery in the lungs by fat, air, blood clot, or tumor cells.

Causes, incidence, and risk factors:

Pulmonary emboli are most often caused by blood clots in the veins, especially veins in the legs or in the pelvis (hips). More rarely, air bubbles, fat droplets, amniotic fluid, or clumps of parasites or tumor cells may obstruct the pulmonary vessels.

The most common cause of a pulmonary embolism is a blood clot in the veins of the legs, called a deep vein thrombosis (DVT). Many clear up on their own, though some may cause severe illness or even death.

Risk factors for a pulmonary embolus include:

• Prolonged bed rest or inactivity (including long trips in planes, cars, or trains)
• Oral contraceptive use
• Surgery (especially pelvic surgery)
• Childbirth
• Massive trauma
• Burns
• Cancer
• Stroke
• Heart attack
• Heart surgery
• Fractures of the hips or femur

Persons with certain clotting disorders may also have a higher risk.