Thrombophlebitis: Blood Clots in Your Legs

When one of your legs becomes swollen and sore, your doctor worries if the swelling is caused by infection, or whether some of the blood inside one of the deep veins of the leg has clotted.

Your doctor's concern about the clot is real, because when a clot forms in the veins of the calf there is a risk that it will extend into the vein in the thigh. If this occurs, then a real risk exists that portions of the clot will break off and lodge in the lungs. The latter situation can be dangerous for life, and requires intensive treatment. Treating the blood clot in the leg is almost without risk and is easy, so recognition of such a clot is important.

What is phlebitis?

Phlebitis describes an inflammation of a vein, whereas thrombophlebitis is an inflammation of a vein with the formation of a blood clot (thrombus). Thrombophlebitis most commonly occurs in the leg, and it may cause pain and redness or swelling of the leg but in some situations it may not produce any symptoms.

How do blood clots occur?

Blood circulates in large and small blood vessels, reaching every corner of the body, bringing life-sustaining nourishment and oxygen to your body's tissues and organs. If blood stops flowing to a sector, that sector dies. Blood is precious, and we try not to lose it. A complex mechanism has developed which seals leaks and prevents loss of too much blood when a blood vessel is damaged. When that system goes awry, clots may form which occlude blood vessels and cause illness.

Blood clots may form when there is injury to the leg, when the blood becomes more likely to clot, such as after lower abdominal surgery or slowing of blood flow in the veins due to long airplane flights, or may occur without obvious provocation. When clots form without provocation, your doctor usually tests to determine if one of the inherited or acquired abnormalities is present which make blood clotting unstable and increase the risk of such clots.

How is phlebitis diagnosed?

When a clot forms in blood that flows slowly (e.g. in a vein), it may or may not cause inflammation along with associated pain, redness, and swelling in the area. It is clearly easier to appreciate the presence of something that hurts and is red and swollen then something which does none of these. Doctors do not know how often clots are silent (without symptoms), but it certainly occurs.

If your doctor suspects you have a blood clot, he or she will try to prove or disprove its presence using a simple and fairly reliable test called a Doppler test. This test uses high-pitched sound waves or ultrasound and has almost completely replaced previous techniques that compressed the leg or injected test materials into it. It is reasonably accurate, not dangerous, and not painful but, as with all tests, will miss some cases.

If clot is found in a deep vein in the leg, your doctor will treat it. Because clots that break off and block blood vessels in the lung are dangerous, your doctor may also choose to test the blood circulation in your lungs using a technique called a V/Q scan. The scan uses radioactive materials to determine if all areas into which you breathe air also are perfused with blood.

Why is treatment necessary?

When a blood clot forms in a vein, a new clot is deposited on it so that the body's defense against such clotting is bypassed. The clot will usually extend until some begins to break off. If clot formation is stopped, the remaining clot will scar and attach to the wall of the vein, usually will become smaller and occasionally will disappear completely. Your doctor will try to stop clot extension by reducing the clotting of the blood, not so much that bleeding will occur but enough to slow things down.

Before treatment was available, many patients died of the complications of phlebitis. Some were dramatic and happened suddenly, for example two to five days after surgery or childbirth when the patient felt well and was ready to go home, all of a sudden the patient died.

Others were not recognized, and people had long periods of shortness of breath, and chest pain, or died without warning. Such events are very uncommon now that measures are taken to prevent and recognize blood clots.

How is phlebitis treated?

Your doctor will treat phlebitis by reducing the tendency of the blood to clot. Since blood clotting is a defense against bleeding, careful control of these treatments is necessary to achieve just the desired effect on the clotting mechanism. How long one must take this type of treatment depends on the cause of the phlebitis and the risk of recurrence.

Clots in veins are usually treated with anticoagulants: heparin, which blocks some of the clotting reactions, or coumarins (warfarin) that cause the body to make less of some of the active proteins which are necessary to form a clot. New "low-molecular weight" heparins are convenient, effective, and in widespread use.

After the clot is controlled, it takes time for the vein to heal so that new clots will not form. For clots that form after surgery or injury, 6 to 12 weeks seems adequate; for those that occur without such provocation, six months seems to be better. Some people have inherited abnormalities of some of the proteins that control clotting, and in them, anticoagulant treatment may have to continue for life.

What are the risks of treatment?

There is probably no medical treatment that does not have some danger. The risk/benefit ratio must always be considered before starting treatment. Predictably, interference with the clotting mechanism may cause bleeding, especially from wounds or surgical sites.

Careful control of how much the anticoagulants have interfered with clotting usually will prevent problems, but bruising or bleeding or blood in the urine if they occur when you take anticoagulants must always be reported to your doctor quickly. Occasionally, an allergic type reaction to heparin may occur which causes clotting rather than stopping it.

Prompt attention to this potentially fatal complication is very important. Even less frequently, in some persons with inherited abnormalities of some clotting proteins (protein C), coumarin treatment may be followed by blueness and even severe damage to fingers, toes, or certain other sites. As indicated above, prompt reporting of such unusual occurrences to your doctor is very important.

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