Blood Clot in the Legs

Deep venous thrombosis (DVT) refers to a blood clot embedded in one of the major deep veins of the lower legs, thighs, or pelvis. A clot blocks blood circulation through these veins, which carry blood from the lower body back to the heart. The blockage can cause pain, swelling, or warmth in the affected leg.

Blood clots in the veins can cause inflammation (irritation) called thrombophlebitis. The most worrisome complications of DVT occur when a clot breaks loose (or embolizes) and travels through the bloodstream and causes blockage of blood vessels (pulmonary arteries) in the lung. This can lead to severe difficulty in breathing and even death, depending on the degree of blockage.

In the United States, about 2 million people per year develop DVT. Most of them are aged 40 years or older. Statistics reveal that at least 200,000 patients die each year from blood clots in their lung.

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

• Damage to the inside of a blood vessel
  
  
• 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 1 or more of these 3 criteria can cause DVT. 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 an injury or during an 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 replacement therapy, or HRT) or birth control pills
  
  
• Malignant tumors (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

If you have one DVT, you are more likely than the average person to have a second DVT.

Symptoms occur in the affected leg when a clot obstructs blood flow and causes inflammation. Symptoms may include the following: 

• Swelling
  
  
• Gradual onset of pain
  
  
• Redness
  
  
• Warm to touch
  
  
• Worsening leg pain when bending the foot
  
  
• Leg cramps, especially at night
  
  
• Bluish or whitish discoloration of skin
  
  

Almost 30-50% of individuals have no complaints.

Call your health care provider immediately if you suspect a clot.

• Although a DVT may resolve on its own, the life-threatening consequences of a clot reaching the lung, called pulmonary embolism, are severe enough to warrant seeking medical attention at once.
  
  
• Your health care provider may tell you to go immediately to a hospital emergency department.

If you have leg pain or swelling with any of the risk factors, go to a hospital emergency department immediately.

Call 911 if you or someone you know with a current DVT, previous DVT, or risk factor begins having chest pain, shortness of breath, difficulty breathing, fainting, or any other symptom that concerns you.

Upon hearing your symptoms, your health care provider will suspect that you have a DVT, especially if you have any of the risk factors.

No accurate blood test is available to diagnose DVT. Therefore, a variety of imaging tests are used to confirm the diagnosis.

• Doppler ultrasound: Using high-frequency sound waves, this system can visualize the large, proximal veins and detects a clot if one is present. Painless and without complications, this is the most commonly used method to diagnose DVT. Sometimes, though, the test can miss finding a clot, especially in the distal, smaller veins.
  
  
• Venography: A liquid dye is injected into the veins. This makes the veins show up better and allows them to be mapped. It highlights blockage of blood flow by a clot. This is the most accurate test, but also the most uncomfortable and invasive. It is rarely done today because of the availability of better Doppler machines.
  
  
• Impedance plethysmography: Electrodes detect volume changes within veins. Because this test detects clots no better than ultrasound and is harder to perform, it is rarely used.
  
  
• CT scan: This is a type of x-ray that gives a very detailed look at the leg veins in cross section and can detect clots. It is, however, rarely used for this purpose as it is more difficult to interpret and is time consuming. The CT scan is more useful to identify blood clots in the lung.

|Self-Care at Home|

Medications are necessary to treat DVT. You must see a medical professional for treatment.

To increase comfort and lower the risk of the clot embolizing and moving to the lung, take the following measures:

• Keep the affected limb elevated.
  
  
• Avoid prolonged sitting or bed rest.
  
  
• Relieve pain by applying warm, moist heat to the area.

|Medical Treatment|

If you have a DVT, you will be treated with a blood-thinning medication (anticoagulant).

• These medications do not make the clot go away. They stabilize the clot and make it adhere to the vessel wall.
  
  
• The body normally lyses (breaks up) the clot on its own. This is a gradual process that may take several days or weeks. 
  
  
• Anticoagulants prevent further clotting and worsening of the condition.
  
  
• They do this by preventing factors in blood from coming together and clotting too easily.

Until very recently, most people were treated with anticoagulants for 3-6 months following their first episode of DVT.

• It isn't that the risk of a second DVT goes away after 6 months, but that the risks of taking these medications outweigh the clot-preventing benefits.
  
  
• Because clotting is the body's natural way of preventing bleeding, these medications increase your risk of bleeding from anywhere in your body. Any trauma, fall, or injury can result in uncontrolled bleeding. 
  
  
• You may have received anticoagulant medication for longer than 6 months if you had a repeat DVT.

Treatment standards changed in early 2003 with the finding that lower doses of anticoagulants would prevent recurrent DVTs.

• That means that it is safe to continue treating people who have had one DVT with clot-preventing medications for much longer than 6 months.
  
  
• The lower doses do not carry such a high bleeding risk.
  
  
• Now the benefits of continuing treatment outweigh the risk of bleeding.
  
  
• One can decrease the chance of having a second DVT without creating such a serious bleeding risk.

If you have a clot above the knee, you most likely will be admitted to a hospital for treatment. While in the hospital, you will be given an anticoagulant medication called heparin (Hep-Lock, Liquaemin). Heparin is available only as a subcutaneous injection or through an IV. It rapidly stops your blood from clotting further. It is generally used only in hospitals and not for home use.

• Another oral anticoagulant, called warfarin (Coumadin), usually is started within 1-3 days. For more information about warfarin, see Medications. You will probably be discharged from the hospital once you have started taking warfarin. Warfarin can be taken as an outpatient.
  
  
• Low molecular weight heparin (Lovenox) is a newer option for treating DVT at home. This form of heparin is given twice daily by injecting into your skin. The pharmacy dispenses the drug in prefilled, easy-to-use syringes. You or a family member will be taught how to give the injections. It is very easy to do, and you don't have to check clotting times.
  
  
• Once you have been discharged, you should return to a hospital emergency department or call 911 if you have any concerns over bleeding, especially if you have red or black bowel movements, red or brown urine, faintness, dizziness, severe headache, or any bleeding that does not stop.

In rare cases, your health care provider may elect to dissolve the clot with special "clot-busting" medications. This is done only when the clot is identified within the first 6-12 hours and rapidly reverses the symptoms of a DVT and pulmonary embolism.

• Because these medications carry a significant risk of causing bleeding, their use for DVT is not first choice.
  
  
• Examples of these medications are urokinase (Abbokinase), streptokinase (Kabikinase, Streptase), or alteplase (Activase).

Some people should not take anticoagulant medication. They include people who have had bleeding in the brain (a type of stroke), recent brain surgery, or bleeding from the gastrointestinal tract. People who also have very high blood pressure or those involved in recent trauma or any recent surgery are not candidates for thrombolytic therapy.

• If you are one of these people, your health care provider may instead recommend placement of a filter in your inferior vena cava, the main vein returning to the heart.
  
  
• This prevents clots in the lower body from traveling to the heart and lungs, where they can do more damage.

|Medications|

Warfarin is by far the most widely used anticoagulant medication.

• It is taken by mouth and thus does not work as quickly as heparin. It takes about 48 hours to become effective.
  
  
• The dosage of warfarin is important for successful treatment. Low doses may not be effective and high doses can cause bleeding. The dosage is adjusted on a daily basis for the first few days and then on a weekly basis. The dosage is adjusted by assessing clotting parameters, which are found in the blood.
  
  
• While taking warfarin, you may undergo frequent blood tests to check your prothrombin time. The prothrombin time is reported in a standardized form called the international normalized ratio (INR). Your health care provider will aim to keep your INR within a certain range (usually between 2-2.5) by adjusting your dose of warfarin.

|Surgery|

Thrombectomy is surgical removal of the clot. Much controversy surrounds using this treatment instead of anticoagulation. Thrombectomy is performed when a large blood clot is obstructing the vessels in the lung and the patient is in critical condition. Surgery is effective, and the results are immediate.

People who cannot take anticoagulant medication may undergo a placement of an umbrellalike device (filter), which is usually placed via the veins in the leg or neck, under local anesthesia.

• A small, metal, umbrellalike filter is inserted into the inferior/superior vena cava, the main large vein that carries blood back to the heart from the upper/lower body.
  
  
• This technique is performed in a hospital.
  
  
• The umbrella should catch any clots that break loose from the veins of your lower body before they travel to your lung.

|Follow-up|

You may be asked to return for follow-up Doppler ultrasounds or other imaging studies if the leg swelling persists of if your symptoms recur.

During anticoagulant treatment, you should take the following measures:

• Take the prescribed amount of medication. Do not miss or add doses.
  
  
• If your health care provider does not explain signs and symptoms of bleeding, ask him or her.
  
  
• Follow your health care provider’s instructions closely about when to get lab checks for blood coagulation.
  
  
• Ask your health care provider before starting or stopping any medication, including over-the-counter medications. Many medicines increase or otherwise interfere with the effect of anticoagulants.
  
  
• Ask about what foods you should avoid, because some foods may change the effectiveness of blood-thinning drugs.
  
  
• Wear a Medic-alert bracelet with information about which anticoagulant you are taking.
  
  
• Inform any other medical professionals, dentist, or podiatrist that you are taking an anticoagulant before any procedure.

|Prevention|

The key to prevention is to reverse any risk factors, as follows:

• If you are obese, try to lose weight.
  
  
• Avoid periods of prolonged immobility.
  
  
• Keep your legs elevated while sitting down or in bed.
  
  
• Avoid high-dose estrogen pills, unless they are deemed necessary by your health care provider.

If you had surgery recently, preventive treatment may be prescribed for you to avoid formation of a clot.

• You may be instructed to get out of bed several times a day during the recovery period.
  
  
• Sequential compression devices (SCDs) may be placed on your legs. Their squeezing action has been shown to reduce the probability of clot formation. You also may be given elastic stockings to wear.
  
  
• Low molecular weight heparin or low-dose warfarin may be prescribed to prevent clot formation.

|Outlook|

Most DVTs resolve on their own.

• However, nearly 20% of untreated DVTs located above the calf embolize to the lung (pulmonary embolus), and 10-20% of those are fatal.
  
  
• More than 90% of life-threatening pulmonary emboli arise from DVTs in the legs.

If you have one DVT, you are more likely than the average person to have another DVT.

• A second DVT occurs within 3 months in 5-8% of people who have had one DVT and within 2 years in 20%.
  
  
• Therefore, you should closely follow the prevention instructions your health care provider gives you.

Anticoagulant therapy lowers the death rate from pulmonary embolism by a 5- to 10-fold factor.

anticoagulants, anticoagulation, deep venous thrombophlebitis, deep venous thrombosis, DVT, emboli, embolism, embolize, embolus, thromboembolism, hypercoagulability, hypercoagulable state, venous blood clot, blood clot in the legs, pulmonary embolism, heparin, warfarin, low molecular weight heparins, vena cava filter, Greenfield filter, thrombectomy, prothrombin time, INR

Author: Shabir Bhimji, MD, Consulting Surgeon, Cardiac Surgical Associates of West Texas.

Coauthor(s): Scott G Weiner, MD, MPH, Assistant Professor, Department of Emergency Medicine, Tufts-New England Medical Center; Jonathan L Burstein, MD, Assistant Professor of Population and International Health, Harvard School of Public Health; Director and Chair, Section of Disaster Medicine, Division of Emergency Medicine, Harvard Medical School; Kathryn L Hale, MS, PA-C, Medical Writer, .com, Inc.

Editors: Alan D Forker, MD, Program Director of Cardiovascular Fellowship, Professor of Medicine, Department of Internal Medicine, University of Missouri at Kansas City School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, ; Steven L Bernstein, MD, Vice-Chair, Academic Affairs, Department of Emergency Medicine, Newark Beth Israel Medical Center; Assistant Professor, Department of Emergency Medicine, Mt Sinai School of Medicine.