Leg clots (aka deep-vein thrombosis): an immediate and long-term health hazard

When it comes to under-the-radar health conditions, deep-vein thrombosis is at the top of the list. Most of my patients have never heard of this common problem. Yet deep-vein thrombosis puts more than one-quarter million Americans in the hospital each year, and complications from it are responsible for upwards of 100,000 deaths.

Deep-vein thrombosis (DVT) is the medical term for a blood clot that forms in a leg vein. Some DVTs cause no symptoms; others hurt, or make the leg swell. There are two big worries with a DVT:

Pulmonary embolism. A piece of a clot can break away, travel through the bloodstream, and become lodged in the lungs. This is called a pulmonary embolism. Almost all DVT-related deaths are due to a pulmonary embolism.

Post-phlebitis syndrome. A clot can permanently damage the vein it is lodged in. This problem, called post-phlebitis syndrome, causes persistent leg pain, swelling, darkened skin, and sometimes hard-to-heal skin ulcers. Up to 40% of people with a DVT develop post-phlebitis syndrome.

Treating DVT

Deep-vein thrombosis is initially treated with an anticoagulant. Today there are many choices, such as one of the newer oral direct acting agents, intravenous heparin or subcutaneous low-molecular weight heparin or fondaparinux. Anticoagulants can stop a DVT from getting larger and can prevent new clots from forming. Use of these drugs substantially decreases the risk of developing a pulmonary embolism.

But anticoagulants can’t quickly dissolve a clot that has already formed. That’s the job of drugs called thrombolytics (commonly known as clot busters), such as streptokinase and alteplase. Studies have had mixed results. However, they are sometimes considered in people with massive leg clots to prevent long-term leg swelling and pain (called post-phlebitis syndrome).

Delivering a clot-dissolving drug directly into the clot—instead of having it circulate through the bloodstream via standard intravenous delivery—allows the use of a lower dose, which decreases the risk of bleeding elsewhere in the body.

Not everyone with a DVT needs direct clot-dissolving therapy. Anticoagulants, along with support stockings to reduce swelling and improve blood flow, are enough for most people. For those with a very large clot, especially one high up in the leg or in the pelvis, direct injection of a thrombolytic agent may help protect the affected vein from post-phlebitis syndrome.

Prevention is preferable to treatment

Anyone can develop a DVT, although some people are more likely to have one than others. You are at increased risk if you or a close family member have had a DVT before, have an inherited condition that causes your blood to clot more readily than normal, have cancer, are immobile for a long time (confined to bed, long-duration plane or car trip, etc.), or use birth control pills.

Here are some good ways that everyone can use to help prevent a DVT from forming:

  • Stay physically active. At work or at home, get up from your chair frequently. Short walks contract the muscles in your legs that help pump blood back toward your heart.
  • Avoid dehydration. This is especially important when you are going to be sitting for a prolonged time, such as in an airplane.
  • Move your legs. If you are bedridden and can’t take frequent walks, contracting your leg muscles will help prevent blood from pooling and clotting.
  • Maintain a healthy body weight. Obesity increases the risk of DVT.
  • If you are hospitalized for some reason, ask your doctors and nurses to make sure you are receiving measures—such as wearing special stockings or getting low-dose heparin—to prevent blood clots.

Related Information: Harvard Heart Letter


  1. Anonymous

    I am always looking online for information on leg clots and some health tips that can facilitate me. Thank you for this information!

  2. Rich LPL Driving

    Hi there, just wanted to say that if you are on a plane or driving your car these days there is no better thing than prevention over cure. Avoiding DVT is the best solution – if you’re reading this and already have DVT then I’m sorry for you. If you don’t – just follow the simple rules.

    When driving – stop every so often, get out and walk about. Go for a snack, use the bathroom, buy a newspaper.
    When flying – get up, go to the toilet, see the cock pit, visit the plane bar or just stole the isles.

  3. Doug W

    Can a blood clot form days after traveling? I had a D-Dimer test and ultra-sound the day afer driving 1200 miles, but still have pain in my calf.

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