Deep vein thrombosis (throm-BO-sis), or DVT, is a
blood clot that forms in a vein deep in the body. Blood clots occur when blood
thickens and clumps together.
Most deep vein blood clots occur in the lower leg or
thigh. They also can occur in other parts of the body.
A blood clot in a deep vein can break off and travel
through the bloodstream. The loose clot is called an embolus. When the clot
travels to the lungs and blocks blood flow, the condition is called
pulmonary
embolism (PULL-mun-ary EM-bo-lizm), or PE.
PE is a very serious condition. It can damage the
lungs and other organs in the body and cause death.
Blood clots in the thigh are more likely to break
off and cause PE than blood clots in the lower leg or other parts of the body.
Blood clots also can form in the veins closer to the
skin's surface. However, these clots won't break off and cause PE.
The animation below shows a deep vein blood clot.
Click the "start" button to play the animation. Written and spoken explanations
are provided with each frame. Use the buttons in the lower right corner to
pause, restart, or replay the animation, or use the scroll bar below the
buttons to move through the frames.
The animation shows how a blood clot
in a deep vein of the leg can break off, travel to the lungs, and block blood
flow.
Other Names for Deep Vein Thrombosis
Blood clot in the legs.
Venous thrombosis.
Venous thromboembolism (VTE). This term is used
for both deep vein thrombosis and
pulmonary
embolism.
What Causes Deep Vein Thrombosis?
Blood clots can form in your body's deep veins
when:
Damage occurs to a vein's inner lining. This
damage may result from injuries caused by physical, chemical, and biological
factors. Such factors include surgery, serious injury, inflammation, or an
immune response.
Blood flow is sluggish or slow. Lack of motion
can cause sluggish or slowed blood flow. This may occur after surgery, if
you're ill and in bed for a long time, or if you're traveling for a long time.
Your blood is thicker or more likely to clot than
usual. Certain inherited conditions (such as factor V Leiden) increase blood's
tendency to clot. This also is true of treatment with hormone replacement
therapy or birth control pills.
Who Is At Risk for Deep Vein Thrombosis?
Many factors increase your risk for deep vein
thrombosis (DVT). They include:
A history of DVT.
Disorders or factors that make your blood thicker
or more likely to clot than normal. Certain inherited blood disorders (such as
factor V Leiden) will do this. This also is true of treatment with hormone
replacement therapy or using birth control pills.
Injury to a deep vein from surgery, a broken
bone, or other trauma.
Slow blood flow in a deep vein from lack of
movement. This may occur after surgery, if you're ill and in bed for a long
time, or if you're traveling for a long time.
Pregnancy and the first 6 weeks after giving
birth.
Recent or ongoing treatment for cancer.
A central venous catheter. This is a tube placed
in vein to allow easy access to the bloodstream for medical treatment.
Being older than 60 (although DVT can occur in
any age group).
Your risk for DVT increases if you have more than
one of the risk factors listed above.
What Are the Signs and Symptoms of Deep Vein
Thrombosis?
The signs and symptoms of deep vein thrombosis (DVT)
may be related to DVT itself or to
pulmonary
embolism (PE). See your doctor right away if you have symptoms of either.
Both DVT and PE can cause serious, possibly life-threatening complications if
not treated.
Deep Vein Thrombosis
Only about half of the people with DVT have
symptoms. These symptoms occur in the leg affected by the deep vein clot. They
include:
Swelling of the leg or along a vein in the leg
Pain or tenderness in the leg, which you may feel
only when standing or walking
Increased warmth in the area of the leg that's
swollen or in pain
Red or discolored skin on the leg
Pulmonary Embolism
Some people don't know they have DVT until they have
signs or symptoms of PE. Symptoms of PE include:
Unexplained shortness of breath
Pain with deep breathing
Coughing up blood
Rapid breathing and a fast heart rate also may be
signs of PE.
How Is Deep Vein Thrombosis Diagnosed?
Your doctor will diagnose deep vein thrombosis (DVT)
based on your medical history, a physical exam, and the results from tests. He
or she will identify your risk factors and rule out other causes for your
symptoms.
Medical History
To learn about your medical history, your doctor may
ask about:
Your overall health
Any prescription medicines you're taking
Any recent surgeries or injuries you've had
Whether you've been treated for cancer
Physical Exam
During the physical exam, your doctor will check
your legs for signs of DVT. He or she also will check your blood pressure and
your heart and lungs.
Diagnostic Tests
You may need one or more tests to find out whether
you have DVT. The most common tests used to diagnose DVT are:
Ultrasound. This is the most common test for
diagnosing deep vein blood clots. It uses sound waves to create pictures of
blood flowing through the arteries and veins in the affected leg.
A D-dimer test. This test measures a substance in
the blood that's released when a blood clot dissolves. If the test shows high
levels of the substance, you may have a deep vein blood clot. If your test is
normal and you have few risk factors, DVT isn't likely.
Venography (ve-NOG-ra-fee). This test is used if
ultrasound doesn't provide a clear diagnosis. Dye is injected into a vein, and
then an x ray is taken of the leg. The dye makes the vein visible on the
x ray. The x ray will show whether blood flow is slow in the vein.
This may indicate a blood clot.
Other less common tests used to diagnose DVT include
magnetic resonance imaging (MRI) and computed tomography (CT) scanning. These
tests provide pictures of the inside of the body.
You may need blood tests to check whether you have
an inherited blood clotting disorder that can cause DVT. You may have this type
of disorder if you have repeated blood clots that can't be linked to another
cause, or if you develop a blood clot in an unusual location, such as a vein in
the liver, kidney, or brain.
If your doctor thinks that you have pulmonary
embolism (PE), he or she may order extra tests, such as a ventilation perfusion
scan (V/Q scan). The V/Q scan uses a radioactive material to show how well
oxygen and blood are flowing to all areas of the lungs.
For more about tests used to diagnose PE, see the
Diseases and Conditions Index
Pulmonary
Embolism article.
How Is Deep Vein Thrombosis Treated?
Goals of Treatment
The main goals of treating deep vein thrombosis
(DVT) are to:
Stop the blood clot from getting bigger
Prevent the blood clot from breaking off and
moving to your lungs
Reduce your chance of having another blood clot
Medicines
Medicines are used to prevent and treat DVT.
Anticoagulants
Anticoagulants (AN-te-ko-AG-u-lants) are the most
common medicines for treating DVT. They're also known as blood thinners.
These medicines decrease your blood's ability to
clot. They also stop existing blood clots from getting bigger. However, blood
thinners can't break up blood clots that have already formed. (The body
dissolves most blood clots with time.)
Blood thinners can be taken as either a pill, an
injection under the skin, or through a needle or tube inserted into a vein
(called intravenous, or IV, injection).
Warfarin and heparin are two blood thinners used to
treat DVT. Warfarin is given in pill form. (Coumadin® is a
common brand name for warfarin.) Heparin is given as an injection or through an
IV tube. There are different types of heparin. Your doctor will discuss the
options with you.
Your doctor may treat you with both heparin and
warfarin at the same time. Heparin acts quickly. Warfarin takes 2 to 3 days
before it starts to work. Once the warfarin starts to work, the heparin is
stopped.
Pregnant women usually are treated with heparin
only, because warfarin is dangerous during pregnancy.
Treatment for DVT with blood thinners usually lasts
from 3 to 6 months. The following situations may change the length of
treatment.
If your blood clot occurred after a short-term
risk (for example, surgery), your treatment time may be shorter.
If you've had blood clots before, your treatment
time may last longer.
If you have certain other illnesses, such as
cancer, you may need to take blood thinners for as long as you have the
illness.
The most common side effect of blood thinners is
bleeding. This happens if the medicine thins your blood too much. This side
effect can be life threatening.
Sometimes, the bleeding is internal (inside your
body). People treated with blood thinners usually receive regular blood tests
to measure their blood's ability to clot. These blood tests are called PT and
PTT tests.
These tests also help your doctor make sure you're
taking the right amount of medicine. Call your doctor right away if you have
easy bruising or bleeding. This may be a sign that your medicines have thinned
your blood too much.
Thrombin Inhibitors
These medicines interfere with the blood clotting
process. They're used to treat blood clots in patients who can't take heparin.
Thrombolytics
These medicines are given to quickly dissolve a
blood clot. They're used to treat large blood clots that cause severe symptoms.
Because thrombolytics can cause sudden bleeding,
they're used only in life-threatening situations.
Other Types of Treatment
Vena Cava Filter
A vena cava filter is used if you can't take blood
thinners or if you're taking blood thinners and still developing blood clots.
The filter is inserted inside a large vein called
the vena cava. The filter catches blood clots that break off in a vein before
they move to the lungs. This prevents
pulmonary
embolism. However, it doesn't stop new blood clots from forming.
Graduated Compression Stockings
These stockings can reduce the swelling that may
occur after a blood clot has developed in your leg. Graduated compression
stockings are worn on the legs from the arch of the foot to just above or below
the knee.
These stockings are tight at the ankle and become
looser as they go up the leg. This creates gentle pressure up the leg. The
pressure keeps blood from pooling and clotting.
These stockings should be worn for at least a year
after DVT is diagnosed.
How Can Deep Vein Thrombosis Be Prevented?
You can take steps to prevent deep vein thrombosis
(DVT).
Your risk of developing DVT while traveling is
small. The risk increases if the travel time is longer than 4 hours, or if you
have other risk factors for DVT.
During long trips, it may help to:
Walk up and down the aisles of the bus, train, or
airplane. If traveling by car, stop about every hour and walk around.
Move your legs and flex and stretch your feet to
encourage blood flow in your calves.
Wear loose and comfortable clothing.
Drink plenty of fluids and avoid alcohol.
If you're at increased risk for DVT, your doctor may
recommend wearing compression stockings during travel or taking a
blood-thinning medicine before traveling.
Living With Deep Vein Thrombosis
If you've had a deep vein blood clot, you're at
greater risk for another one. During treatment and after, it's important
to:
Check your legs for signs and symptoms of DVT.
These include swollen areas, pain or tenderness, increased warmth in swollen or
painful areas, or red or discolored skin on the legs.
Contact your doctor right away if you have signs
and symptoms of DVT.
Ongoing Health Care Needs
Medicines that thin your blood and prevent blood
clots are used to treat DVT. These medicines can thin your blood too much and
cause bleeding (sometimes inside the body). This side effect can be life
threatening.
Bleeding may occur in the digestive system or the
brain. Signs and symptoms of bleeding in the digestive system include:
Bright red vomit or vomit that looks like coffee
grounds
Bright red blood in your stools or black, tarry
stools
Pain in your abdomen
Signs and symptoms of bleeding in the brain
include:
Severe pain in your head
Sudden changes in your vision
Sudden loss of movement in your arms or legs
Memory loss or confusion
If you have any of these signs or symptoms, get
treatment right away.
You also should seek treatment right away if you
have a lot of bleeding after a fall or injury. This could be a sign that your
DVT medicines have thinned your blood too much.
Talk to your doctor before taking any medicines
other than your DVT medicines. This includes over-the-counter medicines.
Aspirin, for example, also can thin your blood. Taking two medicines that thin
your blood may raise your risk for bleeding.
Ask your doctor about how your diet affects these
medicines. Foods that contain vitamin K can change how warfarin (a
blood-thinning medicine used to treat DVT) works. Vitamin K is found in green,
leafy vegetables and some oils, like canola and soybean oil. Your doctor can
help you plan a balanced and healthy diet.
Discuss with your doctor whether drinking alcohol
will interfere with your medicines. Your doctor can tell you what amount of
alcohol is safe for you.
Key Points
Deep vein thrombosis (DVT) is a blood clot that
forms in a vein deep in the body. Most deep vein blood clots occur in the lower
leg or thigh. They also can occur in other parts of the body.
A blood clot in a deep vein can break off, travel
through the bloodstream to the lungs, and block blood flow. This condition is
called pulmonary
embolism (PE). PE is a very serious condition that can cause death.
Blood clots can form in your body's deep veins
when:
Damage occurs to a vein's inner lining
Blood flow is sluggish or slow
Your blood is thicker or more likely to clot
than usual
Many factors increase your risk for DVT. People
who have had DVT before or have more than one risk factor are at increased risk
for the condition.
Only about half the people with DVT have
symptoms. These symptoms occur in the leg affected by the deep vein clot. They
include swelling of the leg or along a vein in the leg, pain or tenderness in
the leg, increased warmth in the area of the leg that's swollen or in pain, and
red or discolored skin on the leg.
Other symptoms may relate to PE. These may
include unexplained shortness of breath, pain with deep breathing, and coughing
up blood.
Your doctor will diagnose DVT based on your
medical history, a physical exam, and the results from tests. He or she will
identify your risk factors and rule out other causes for your symptoms.
DVT is treated with medicines that thin the
blood, interfere with the blood clotting process, and dissolve blood clots.
Other treatments include filters to catch blood clots and compression stockings
that prevent blood from pooling and clotting.
You can take steps to prevent DVT. See your
doctor regularly. Follow your treatment plan as your doctor prescribes, stay
active if possible, and exercise your lower leg muscles during long trips.
Contact your doctor at once if you have any
symptoms of DVT or PE.
Links to Other Information About Deep Vein
Thrombosis
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