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thrombosis

thrombosis (thrŏmbō´sĬs), obstruction of an artery or vein by a blood clot (thrombus). Arterial thrombosis is generally more serious because the supply of oxygen and nutrition to an area of the body is halted. Thrombosis of one of the arteries leading to the heart (heart attack; see infarction) or of the brain (stroke) can result in death and, in a vessel of the extremities, may be followed by gangrene. Acute arterial thrombosis often results from the deposition of atherosclerotic material in the wall of an artery, which gradually narrows the channel, precipitating clot formation (see arteriosclerosis). A thrombus that breaks off and circulates through the bloodstream is called an embolus.

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Thrombosis

Thrombosis

How Does Thrombosis Happen?

What Are the Signs and Symptoms of Thrombosis?

How Do Doctors Diagnose and Treat Thrombosis?

Resource

Thrombosis is the formation of a blood clot, called a thrombus, that blockspart or all of a blood vessel, such as a vein.

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Cardiovascular system

Circulatory system

Within moments after a finger is cut, platelets in the blood begin to gather at the injury. Platelets are tiny disc-shaped cells in the blood, much smaller than even a red blood cell. The platelets react with calcium and with other substances in the bodys tissues to form a semi-solid, stringy protein. The cut covers with a scab and eventually heals. For injuries like cuts, clots are good things. But when clots form inside blood vessels, the condition is called thrombosis, and it can be life threatening.

How Does Thrombosis Happen?

Phlebitis

Thrombosis usually begins as an inflammation of the vein known as phlebitis*. Phlebitis develops when blood flows slowly or pools in veins. This usually occurs in the legs and causes injury to the walls of the vein. Just as platelets gather to form clots on cut fingers, they also may start to form clots along the injured walls of veins. People with phlebitis may experience pain and tenderness along the vein, skin discoloration, swelling and edema, a rapid pulse, and mild fever. If untreated, many people with phlebitis develop thrombosis in the inflamed vein.

* phlebitis
(fle-BY-tis) refers to inflammation of a vein.

Causes

There are many possible causes. Inactivity, such as sitting for long periods of time or resting in bed, is a major cause. Surgery, tumors*, and injuries to the leg also may cause thrombosis. Certain infections and cancers may alter the clotting substances in the blood and cause thrombosis.

* tumor
refers to an abnormal growth of body tissue. Tumors may or may not be cancerous.

Women are especially at risk, because the female hormone estrogen is linked to thrombosis. Pregnant women have very high levels of estrogen. Estrogen is also found in birth control pills and in the hormone replacement medications that some women use after menopause, although thromboses due to these medications are not very common.

What Are the Signs and Symptoms of Thrombosis?

The major symptoms of thrombosis are pain in the affected area and swelling, which can occur suddenly. If the thrombosis involves a leg vein, the leg also might appear red and feel warm to the touch. Veins close to the skin surface may look larger than normal and reddish-blue in color.

The biggest danger is when a clot forms in the large veins that are deep within the legs. If the blood clot grows, it may break off. The clot may then travel toward and then through the heart and block the pulmonary* artery, which is a major blood vessel, causing a pulmonary embolism*. This serious complication of thrombosis may cause death if not treated rapidly and effectively.

* pulmonary
refers to the lungs.
* embolism
is a blockage in a blood vessel caused by a blood clot air bubble, fatty tissue, or other substance that traveled through the bloodstream from another part of the body.

How Do Doctors Diagnose and Treat Thrombosis?

Doctors use several tests to determine if patients have thrombosis. They may inject a dye into the veins and then use an x-ray to look for clots. They may use an ultrasound machine, which uses sound waves to create an internal view of veins similar to an x-ray. Or they may test blood pressure above and below the suspected location of the clot to measure differences.

Thrombosis can be treated with medications that prevent the blood from clotting as easily. This can stop the clot from growing larger and lower the risk that the clot will break free and cause an embolism. Clot-dissolving drugs also may be injected into the vein. A procedure called balloon angioplasty widens the vein around the clot by inserting and inflating a small balloon that pushes out the narrow walls of the vein. Another surgery involves inserting a small, mesh tube within the vein to keep it open.

For people at high risk for developing thrombosis, doctors sometimes recommend preventive measures such as the use of drugs that interfere with blood clotting and special compression stockings that help keep blood from pooling in the deep veins of the legs.

See also

Clotting

Embolism

Phlebitis

Stroke

Resource

The Venous Educational Institute of North America posts information and graphics about clots and surgical procedures at its website. http://www.venous-info.com/

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thrombosis

thrombosis (throm-boh-sis) n. a condition in which the blood changes from a liquid to a solid state in the cardiovascular system and produces a mass of coagulated blood (thrombus). Thrombosis in an artery obstructs the blood flow to the tissue it supplies (see coronary thrombosis, stroke). Thrombosis can also occur in a vein (deep vein t.; see phlebothrombosis), and it may be associated with inflammation (see thrombophlebitis).

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thrombosis

throm·bo·sis / [unvoicedth]rämˈbōsis/ • n. (pl. -ses / -ˌsēz/ ) local coagulation or clotting of the blood in a part of the circulatory system: increased risk of thrombosis | he died of a coronary thrombosis. DERIVATIVES: throm·bot·ic / -ˈbätik/ adj.

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thrombosis

thrombosis (path.) coagulation of the blood. XVIII. — Gr. thrómbōsis curdling, f. thromboûsthai become curdled or clotted, f. thrómbos, lump, clot. whence thrombus XVII; see- -OSIS.

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thrombosis

thrombosis Formation of a blood clot in an artery or vein. Besides causing loss of circulation to the area supplied by the blocked vessel, it carries the risk of embolism.

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thrombosis

thrombosis The obstruction of a blood vessel by a mass of blood cells and fibrin (thrombus), which can result from excessive blood clotting.

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thrombosis

thrombosis Formation of blood clots in blood vessels.

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thrombosis

thrombosisglacis, Onassis •abscess •anaphylaxis, axis, praxis, taxis •Chalcis • Jancis • synapsis • catharsis •Frances, Francis •thesis • Alexis • amanuensis •prolepsis, sepsis, syllepsis •basis, oasis, stasis •amniocentesis, anamnesis, ascesis, catechesis, exegesis, mimesis, prosthesis, psychokinesis, telekinesis •ellipsis, paralipsis •Lachesis •analysis, catalysis, dialysis, paralysis, psychoanalysis •electrolysis • nemesis •genesis, parthenogenesis, pathogenesis •diaeresis (US dieresis) • metathesis •parenthesis •photosynthesis, synthesis •hypothesis, prothesis •crisis, Isis •proboscis • synopsis •apotheosis, chlorosis, cirrhosis, diagnosis, halitosis, hypnosis, kenosis, meiosis, metempsychosis, misdiagnosis, mononucleosis, myxomatosis, necrosis, neurosis, osmosis, osteoporosis, prognosis, psittacosis, psychosis, sclerosis, symbiosis, thrombosis, toxoplasmosis, trichinosis, tuberculosis •archdiocese, diocese, elephantiasis, psoriasis •anabasis • apodosis •emphasis, underemphasis •anamorphosis, metamorphosis •periphrasis • entasis • protasis •hypostasis, iconostasis

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Thrombosis

Thrombosis

Thrombosis is the formation of a blood clot (thrombus) in a blood vessel. The process is an exaggeration of a normal and useful event by which the body prevents the loss of blood from veins and arteries as a result of an injury. During thrombosis, the blood

clotting process goes beyond the construction of a blockage for a damaged blood vessel and actually produces a solid clump (the clot) that reduces or even interrupts the flow of blood in the blood vessel.

Thrombosis most commonly occurs for several reasons. First, the bloods normal clotting system may become more active with the result that clots within a vein or artery are more likely to form. After childbirth, for example, a womans clotting mechanism becomes more active to reduce her loss of blood. If the system becomes too efficient, however, clots may form within a blood vessel.

Secondly, a reduction in blood circulation can also result in the production of a clot. Primitive clots that might otherwise be swept away by the normal flow of blood may be left undisturbed on a vessel wall, allowing them to develop in size.

Finally, the normal aging of blood vessels may contribute to the formation of clots. The first signs of atheroma, or degeneration of blood vessels, can be observed as early as childhood. The more advanced stagehardening of the arteriesusually does not become a medical problem until old age, however. At this state, scarring of the interior walls of veins and arteries provides sites on which clots can begin to form.

A variety of medical problems can result from thrombosis depending on the location of the thrombus. When thrombosis occurs in a coronary artery of the heart, the result is a myocardial infarction, otherwise known as a heart attack. If a thrombus forms in the brain, a stroke occurs. Thrombosis in a leg vein, especially the long saphenous vein, causes the condition known as venous thrombosis or phlebitis.

A secondary consideration in thrombosis is the possibility that a piece of the thrombus may become detached and carried away by the blood. The embolus thus formed may lodge in another part of the body, such as the lungs, where it may cause further medical problems.

Researchers have identified a number of conditions that may lead to thrombosis. These include ones genetic make-up, bodily injury, surgery, pregnancy, smoking, stress, hypertension, and arteriosclerosis.

The most suitable form of treatment depends on the form of thrombosis that occurs. With phlebitis, for example, bed rest and elevation of the limb is recommended. In some instances, by-pass surgery may be required. For many cases of thrombosis, anticoagulant drugsdrugs that reduce the rate of blood clottingcan also be effective.

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Thrombosis

Thrombosis

Thrombosis is the formation of a blood clot, or thrombus, in a blood vessel. The process is an exaggeration of a normal and useful event by which the body prevents the loss of blood from veins and arteries as a result of an injury. During thrombosis, the blood clotting process goes beyond the construction of a blockage for a damaged blood vessel and actually produces a solid clump (the clot) that reduces or even interrupts the flow of blood in the blood vessel.

Thrombosis most commonly occurs for one of three reasons. First, the blood's normal clothing system may become more active with the result that clots within a vein or artery are more likely to form. After childbirth, for example, a woman's clotting mechanism becomes more active to reduce her loss of blood. If the system becomes too efficient, however, clots may form within a blood vessel.

A reduction in blood circulation can also result in the production of a clot. Primitive clots that might otherwise be swept away by the normal flow of blood may be left undisturbed on a vessel wall, allowing them to develop in size.

Finally, the normal aging of blood vessels may contribute to the formation of clots. The first signs of atheroma, or degeneration of blood vessels, can be observed as early as childhood. The more advanced stage—hardening of the arteries—usually does not become a medical problem until old age, however. At this state, scarring of the interior walls of veins and arteries provides sites on which clots can begin to form.

A variety of medical problems can result from thrombosis depending on the location of the thrombus. When thrombosis occurs in a coronary artery of the heart , the result is a myocardial infarction, otherwise known as a heart attack. If a thrombus forms in the brain , a stroke occurs. Thrombosis in a leg vein, especially the long saphenous vein, causes the condition known as venous thrombosis or phlebitis.

A secondary consideration in thrombosis is the possibility that a piece of the thrombus may become detached and carried away by the blood. The embolus thus formed may lodge in another part of the body, such as the lungs, where it may cause further medical problems.

Researchers have identified a number of conditions that may lead to thrombosis. These include one's genetic make-up, bodily injury, surgery , pregnancy, smoking, stress , hypertension , and arteriosclerosis .

The most suitable form of treatment depends on the form of thrombosis that occurs. With phlebitis, for example, bed rest and elevation of the limb is recommended. In some instances, by-pass surgery may be required. For many cases of thrombosis, anticoagulant drugs—drugs that reduce the rate of blood clotting—can also be effective.

See also Circulatory system.

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