May 26, 2017
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Deep Vein Thrombosis (DVT, Blood Clot in the Legs)

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Deep vein thrombosis (DVT) definition and facts

  • There are both superficial and deep veins in the limbs or extremities (arms and legs). A blood clot in the deep veins is a concern because it can cause life-threatening complications.
  • A blood clot (thrombus) in the deep venous system of the leg becomes dangerous if a piece of the blood clot breaks off or travels through the blood stream, through the heart, and into the pulmonary arteries forming a pulmonary embolism. A person may not have signs or symptoms of a small pulmonary embolism (blood clot in the lungs), but a large embolism can be fatal.
  • Risk factors for blood clot formation include immobility, a genetic tendency toward blood clotting, and injury to veins or adjacent tissues occurs.
  • Symptoms of deep vein thrombosis include:
    • pain,
    • swelling,
    • warmth,
    • tenderness, and
    • redness of the leg or arm.
  • The diagnosis of DVT can be suggested by blood tests and confirmed by ultrasound or other imaging tests.
  • Treatment of DVT typically involves blood thinning medications (anticoagulants) unless they cannot be used in a patient (contraindicated). In that situation, an inferior vena cava filter is potentially considered.
  • Complications of DVT include pulmonary embolism (PE) and post-phlebitic syndrome.
  • There are other types of thrombosis such as:
    • cerebral venous thrombosis (CVT),
    • portal vein thrombosis, and
    • cavernous sinus thrombosis.

What is deep vein thrombosis (DVT)?

A deep vein thrombosis describes a blood clot that forms in the deep veins located in the arm or leg. It is important to know the body's anatomy and function to understand why clots form in veins and why they can be dangerous.

  • Arteries have thin muscles within their walls to be able to withstand the pressure of the heart pumping blood to the far reaches of the body. Veins don't have a significant muscle lining, and there is nothing pumping blood back to the heart except physiology. Blood returns to the heart because the body's large muscles squeeze the veins as they contract in their normal activity of moving the body. The normal activities of moving the body returns the blood back to the heart. Being mobile causes this blood return system to fail, and the resulting stagnated blood may clot.
  • There are two types of veins in the arm or leg; superficial veins and deep veins. Superficial veins lie just below the skin and are easily seen on the surface. Deep veins, as their name implies, are located deep within the muscles of the extremity. Blood flows from the superficial veins into the deep venous system through small perforator veins. Superficial and perforator veins have one-way valves within them that allow blood to flow only in the direction of the heart when the veins are squeezed.
  • A blood clot (thrombus) in the deep venous system of the leg or arm, in itself, is not dangerous. It becomes potentially life-threatening when a piece of the blood clot breaks off and embolizes, travels through the circulation system through the heart, and enters into one of the pulmonary arteries and becomes lodged. This can prevent blood from flowing properly through the lung and decreasing the amount of oxygen absorbed and distributed back to the body.
  • Diagnosis and treatment of a deep venous thrombosis (DVT) is meant to prevent pulmonary embolism.
  • Blood clots in the superficial veins do not pose a danger of causing pulmonary emboli because the perforator vein valves act as a sieve to prevent clots from entering the deep venous system. They are usually not at risk of causing pulmonary embolism.

What does DVT (blood clot) look like?

Picture of how red blood cells and platelets form a blood clot
Picture of how red blood cells and platelets form a blood clot
Medically Reviewed by a Doctor on 9/16/2016


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