Deep Vein Thrombosis Causes

Three factors may lead to formation of a clot inside a blood vessel.

• Damage to the inside of a blood vessel due to trauma or other conditions
  
  
• Changes in normal blood flow, including unusual turbulence, or partial or complete blockage of blood flow
  
  
• Hypercoagulability, a rare state in which the blood is more likely than usual to clot

Any component that contributes to one or more of these three criteria can cause deep vein thrombosis. The more common risk factors are as follows:

• Prolonged sitting, such as during a long plane or car ride
  
  
• Prolonged bed rest or immobility, such as after injury or during illness (stroke)
  
  
• Recent surgery, particularly orthopedic, gynecologic, or heart surgery
  
  
• Recent trauma to the lower body, such as fractures of the bones of the hip, thigh, or lower leg
  
  
• Obesity
  
  
• Heart attack or heart failure
  
  
• Recent childbirth
  
  
• Being at very high altitude, greater than 14,000 feet
  
  
• Use of estrogen replacement (hormone therapy, or HT) or birth control pills
  
  
• Cancer
  
  
• Rare inherited genetic changes in certain blood clotting factors
  
  
• Disseminated intravascular coagulation (DIC), a medical condition in which blood clotting occurs inappropriately, usually caused by overwhelming infection or organ failure
  
  
• Certain heart or respiratory conditions
  
  
• Advanced age

If an individual has one deep vein thrombosis, they are more likely to have a second deep vein thrombosis.