Deep Vein Thrombosis

What is Deep Vein Thrombosis (DVT)?

Deep vein thrombosis, commonly referred to as “DVT,” occurs when a blood clot, or thrombus, develops in the large veins of the legs or pelvic area. Some DVTs may cause no pain, whereas others can be quite painful. With prompt diagnosis and treatment, the majority of DVTs are not life threatening. However, a blood clot that forms in the invisible “deep veins” can be an immediate threat to your life, as compared to a clot that forms in the visible “superficial” veins, the ones beneath your skin. A clot that forms in the large, deep veins is more likely to break free and travel through the vein. It is then called an embolus. When an embolus travels from the legs or pelvic areas and lodges in a lung artery, the condition is known as a “pulmonary embolism,” or PE, a potentially fatal condition if not immediately diagnosed and treated.

What are the causes of DVT?

Generally, a DVT is caused by a combination of two or three underlying conditions:

  • slow or sluggish blood flow through a deep vein
  • a tendency for a person’s blood to clot quickly
  • irritation or inflammation of the inner lining of the vein.

There are a variety of settings in which this clotting process can occur. First, individuals on bed rest (such as during or after a surgical procedure or medical illness, such as heart attack or stroke), or confined and unable to walk (such as during prolonged air or car travel) are common settings. It can occur in certain families in whom there is a history of parents or siblings who have suffered from prior blood clots. It can also occur in individuals whom active cancer or its treatment may predispose the blood to clotting.

Having a recent major surgical procedure, especially a hip and knee orthopedic surgeries or those requiring prolonged bed rest, predispose the blood to clotting. Irritation or inflammation occurs when a leg vein is injured by a major accident or medical procedure.

Also, there are specific medical conditions that may increase your risk of developing a DVT via these three mechanisms, such as congestive heart failure, severe obesity, chronic respiratory failure, a history of smoking, varicose veins, pregnancy and estrogen treatment. If you are concerned that you may be at risk due to any of these conditions, please consult with your physician.

Read the Surgeon General’s “Call to Action to Prevent Deep Vein Thrombosis and Pulmonary Embolism.”

Order, print, or read our Focus on Blood Clots brochure.