Blood clotting is a normal process
to prevent bleeding. The body makes blood clots and then breaks them down. Under certain
circumstances, the body may be unable to break down a clot. This may result in a serious
When blood clots in a vein, it may
be due to the slowed blood flow, an abnormality in clot forming, or from an injury to
the blood vessel wall.
Blood clots can form in arteries
and veins. Clots formed in veins are called venous clots. Veins of the legs can be
superficial veins (close to the surface of the skin) or deep veins (located near the
bone and surrounded by muscle).
Venous clots most often happen in
the deep veins of the legs. This is called deep vein thrombosis (DVT). Once a clot has
formed in the deep veins of the leg, there is a potential for part of the clot to break
off and travel through the blood to another area of the body, often the lung. DVT is the
most common cause of a pulmonary embolism.
Other less-common causes include:
- A fat embolus (often due to the breaking of a large bone)
- Amniotic fluid embolus
- Air bubbles
- Deep vein thrombosis in the upper body
- Clots on an indwelling intravenous (iv) catheter that break off
and travel to the lungs