Blood Clots (Phlebitis)

Blood Clots (Phlebitis) 2017-09-29T02:39:53+00:00

Blood clots in the veins of the legs are frequently called phlebitis or thrombophlebitis. This is a potentially dangerous condition that may affect any vein in the body but is most frequent in the lower extremity veins. Blood clots in the legs are frequent problems occurring in about 2 million extremities each year in the USA. Their seriousness varies from a minor nuisance to a serious threat to life and a leading cause of death in hospital patients.

Awareness of the potential for blood clots is important for everyone because they may be a risk to health and life. The symptoms of acute phlebitis are often very mild, and sometimes there are no symptoms at all. Swelling or pain in one leg that is not explained by other cause should be investigated promptly with an ultrasound examination. Early diagnosis and treatment results in safety for the immediate problem and prevention of death in nearly all cases; it also is the best way to minimize the late long-term effects on the lower leg.


Blood clots can present as red tender lines on the legs or they can develop silently and grow extensively in the deep veins of the leg before being discovered. They are suspected by the physician when there is swelling or pain in just one leg that is not explainable by any other cause such as an injury or other event. The diagnosis requires an ultrasound examination for positive identification. This should be done for any extremity in which unexplainable symptoms of swelling or pain occurs.

Phlebitis occurs in superficial veins just under the skin or deep veins in the muscles of the legs. Superficial phlebitis is easily seen as an area of inflammation that is tender and red and swollen, and feels usually like an oblong lump near the skin. It often occurs in legs that have varicose veins. This kind of phlebitis is easier to diagnose and less serious than the phlebitis that develops in the deep veins where it has a high tendency to extend up and down the leg and give rise to pieces that break off and travel to the lungs.

In all cases the diagnosis is made by ultrasound testing when one leg is enlarged or tender.

Modern ultrasound has provided an ideal method of diagnosing blood clots in the extremities. This test is called ‘duplex scanning’; it is painless, non-invasive, affordable, and widely available throughout the world. It provides an actual picture of the blood clot on a computer screen and has become the standard of diagnosis for blood clots in the legs. When the diagnosis is made it is important to determine the length of the blood clot and the exact veins that are involved. If it is limited to the superficial veins just under the skin it is less dangerous than if it involves the deep veins buried in the muscles of the lower extremities. These are termed superficial phlebitis and deep phlebitis respectively.

Blood clots in the veins can be very long extending from the calf (where they most frequently begin) up to the groin or even into the abdomen. As the clot is found closer to the heart—in the thigh or abdomen—it becomes more and more likely to give rise to pieces that break off and go to the lungs.


Management of superficial phlebitis is simpler than deep phlebitis because superficial phlebitis has fewer serious consequences. No phlebitis, however, should be considered inconsequential and ignored because the problem is often found in both deep and superficial veins in the same or other leg; it may be symptomatic in the leg with mild superficial phlebitis at the same time it is ‘silent’ in another place that harbors a dangerous deep vein blood clot.

Superficial phlebitis involves the veins under the skin but outside of the muscles of the extremity. It is diagnosed by ultrasound which should be done in both legs. If there is no deep phlebitis, the superficial clot can be treated with elastic stockings for support of the leg, simple anti-inflammatory medications, and observation to be sure it does not extend too close to the groin or develop in the deep veins. Antibiotics and anticoagulants are seldom needed. It should resolve in a few days to a week or so. If it extends into the thigh toward the groin it warrants consideration for anticoagulants or interruption of the vein to prevent its extension into the deep central veins.

Blood clots that involve the deep veins in the calf are frequent and are silent most of the time. They tend to grow toward the groin and when they get to the knee level and above they become more and ore dangerous. If they involve the veins of the groin or above they give rise to embolisms in the lungs over half of the time and are a risk to health and life. As deep blood clots heal they leave scars in the deep veins over half of the time. These scars cause long term swelling and pain in the legs that may last a lifetime; some of these become disabling after several years have passed.

Because of these serious a effects of deep vein clots early diagnosis and intense treatment with medications to limit the growth of the clots is very important.

Fortunately, there are excellent medications called anticoagulants to limit the growth of the blood clots and even some that can melt the clots. These anticoagulants prevent 97% of the embolisms to the lungs and save many lives. For some blood clots in more central veins there are medications that can dissolve the blood clots, and in occasional instances surgical removal of blood clots in the groin and above is helpful.

The most important message about blood clots is to diagnose them early and treat them aggressively because this will limit the danger of embolism and minimize the damage to the deep veins that causes late swelling, pain and disability. Blood clots are more likely to occur in older persons, patients at bed rest, individuals with cancer or with surgical procedures on the hip or knee. They have also been identified in people who travel long air flights, especially if there is a problem in the leg before the flight begins.