Thrombosis
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2008-07-14T19:26:50Z
Cyclonenim
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grammar fix
{{Unreferenced|date=March 2008}}
{{Infobox_Disease |
Name = Thrombosis |
Image = |
Caption = |
DiseasesDB = |
ICD10 = {{ICD10|I|80||i|80}}-{{ICD10|I|82||i|80}} |
ICD9 = {{ICD9|437.6}}, {{ICD9|453}}, {{ICD9|671.5}}, {{ICD9|671.9}}|
ICDO = |
OMIM = |
MedlinePlus = |
eMedicineSubj = |
eMedicineTopic = |
MeshID = D013927 |
}}
'''Thrombosis''' is the formation of a [[clot]] or [[thrombus]] within the [[lumen]] of a [[blood vessel]], obstructing the flow of [[blood]] through the [[circulatory system]]. '''Thromboembolism''' is a general term describing both thrombosis and its main complication which is [[embolism|embolisation]].
When a thrombus occupies more than 75% of surface area of the lumen of an artery, blood flow to the [[Tissue (anatomy)|tissue]] supplied is reduced enough to cause symptoms because of decreased [[oxygen]] ([[hypoxia]]) and accumulation of metabolic products like [[lactic acid]]. More than 90% of obstruction can result in [[anoxia]], the complete deprivation of oxygen, and [[infarction]], a mode of death of [[cell (biology)|cell]]s.
==Causes==
In classical terms, thrombosis is caused by abnormalities in one or more of the following ([[Rudolf Virchow|Virchow]]'s triad):
* The composition of the blood (hypercoagulability)
* Quality of the vessel wall (endothelial cell injury)
* Nature of the blood flow (hemostasis)
The formation of a thrombus is usually caused by Virchow's triad. To elaborate, the pathogenesis includes: an injury to the vessel's wall (such as by trauma, infection, or turbulent flow at bifurcations); by the slowing or stagnation of blood flow past the point of injury (which may occur after long periods of sedentary behavior - for example, sitting on a long airplane flight); by a blood state of hypercoagulability (caused for example, by genetic deficiencies or autoimmune disorders).
==Classification==
There are two distinct forms of thrombosis, each of which can be presented by several subtypes.
===Venous thrombosis===
{{main|Venous thrombosis}}
Venous thrombosis is the formation of a thrombus (blood clot) within a [[vein]]. There are several diseases which can be classified under this category:
====Deep vein thrombosis====
{{main|Deep vein thrombosis}}
Deep vein thrombosis (DVT) is the formation of a blood clot within a [[deep vein]]. It most commonly affects leg veins, such as the [[femoral vein]]. Three factors are important in the formation of a blood clot within a deep vein—these are the rate of blood flow, the thickness of the blood and qualities of the vessel wall. Classical signs of DVT include [[swelling]], pain and redness of the affected area.
====Portal vein thrombosis====
{{main|Portal vein thrombosis}}
Portal vein thrombosis is a form of venous thrombosis affecting the [[hepatic portal vein]], which can lead to portal [[hypertension]] and reduction of the blood supply to the liver. It ususally has a pathological cause such as [[pancreatitis]], [[cirrhosis]], [[diverticulitis]] or [[cholangiocarcinoma]].
====Renal vein thrombosis====
{{main|Renal vein thrombosis}}
Renal vein thrombosis is the obstruction of the [[renal vein]] by a thrombus. This tends to lead to reduced drainage from the kidney. [[Anticoagulation]] therapy is the treatment of choice.
====Budd-Chiari syndrome====
{{main|Budd-Chiari syndrome}}
Budd-Chiari syndrome is the blockage of the [[hepatic vein]] or the [[inferior vena cava]]. This form of thrombosis presents with [[abdominal pain]], [[ascites]] and [[hepatomegaly]]. Treatment varies between drug therapy and surgical intervention by the use of [[shunt]]s.
====Paget-Schroetter disease====
{{main|Paget-Schroetter disease}}
Paget-Schroetter disease is the obstruction of an [[upper extremity]] vein (such as the [[axillary vein]] or [[subclavian vein]]) by a thrombus. The condition usually comes to light after vigorous exercise and usually presents in younger, otherwise healthy people. Men are affected more than women.
====Cerebral venous sinus thrombosis====
{{main|Cerebral venous sinus thrombosis}}
Cerebral venous sinus thrombosis (CVST) is a rare form of [[stroke]] which results from the blockage of the [[dural venous sinuses]] by a thrombus. Symptoms may include [[headache]], abnormal vision, any of the symptoms of stroke such as weakness of the face and limbs on one side of the body and [[seizures]]. The diagnosis is usually made with a [[Computed Tomography|CT]] or [[Magnetic Resonance Imaging|MRI scan]]. The majority of persons affected make a full recovery.
===Arterial thrombosis===
Arterial thrombosis is the formation of a thrombus within an [[artery]]. In most cases, arterial thrombosis follows rupture of [[atheroma]], and is therefore referred to as ''atherothrombosis''. There are two diseases which can be classified under this category:
====Stroke====
{{main|Stroke}}
A stroke is the rapid decline of brain function due to a disturbance in the supply of blood to the brain. This can be due to [[ischemia]], thrombus, [[embolus]] (a lodged particle) or [[hemorrhage]] (a bleed). In thrombotic stroke, a thrombus (blood clot) usually forms around [[atherosclerotic]] plaques. Since blockage of the artery is gradual, onset of symptomatic thrombotic strokes is slower. Thrombotic stroke can be divided into two categories—large vessel disease and small vessel disease. The former affects vessels such as the [[internal carotid]]s, [[vertebral]] and the [[circle of Willis]]. The latter can affect smaller vessels such as the branches of the circle of Willis.
====Myocardial infarction====
{{main|Myocardial infarction}}
Myocardial infarction (MI) is caused by an [[infarct]] (death of tissue due to ischemia), often due to the obstuction of the [[coronary artery]] by a thrombus. MI can quickly become fatal if emergency medical treatment is not recieved promptly. If diagnosed within 12 hours of the initial episode (attack) then [[thrombolysis|thrombolytic therapy]] is initiated.
==Embolisation==
If a bacterial infection is present at the site of thrombosis, the thrombus may break down, spreading particles of infected material throughout the [[circulatory system]] ([[pyemia]], [[septic embolus]]) and setting up metastatic abscesses wherever they come to rest. Without an infection, the thrombus may become detached and enter circulation as an [[Embolism|embolus]], finally lodging in and completely obstructing a blood vessel (an [[infarction]]). The effects of an infarction depend on where it occurs.
Most thrombi, however, become [[Fibrinolysis|organized into fibrous tissue]], and the thrombosed vessel is gradually recanalized.
==Prevention==
Thrombosis and embolism can be partially prevented with anticoagulants in those deemed at risk. Generally, a risk-benefit analysis is required, as all anticoagulants lead to a small increase in the risk of major bleeding. In [[atrial fibrillation]], for instance, the risk of [[stroke]] (calculated on the basis of additional risk factors, such as advanced age and [[hypertension|high blood pressure]]) needs to outweigh the small but known risk of major bleeding associated with the use of [[warfarin]].<ref>{{NICE|36|Atrial fibrillation|June 2006}}</ref>
In people admitted to hospital, thrombosis is a major cause for complications and occasionally death. In the UK, for instance, the Parliamentary [[Health Select Committee]] heard in 2005 that the annual rate of death due to hospital-acquired thrombosis was 25,000.<ref name=Hunt>{{cite journal |author=Hunt BJ |title=Awareness and politics of venous thromboembolism in the United kingdom |journal=Arterioscler. Thromb. Vasc. Biol. |volume=28 |issue=3 |pages=398–9 |year=2008 |month=March |pmid=18296598 |doi=10.1161/ATVBAHA.108.162586 |url=http://atvb.ahajournals.org/cgi/content/full/28/3/398}}</ref> In patients admitted for surgery, graded [[compression stockings]] are widely used, and in severe illness, prolonged immobility and in all [[orthopedic surgery]], [[clinical practice guideline|professional guidelines]] recommend [[low molecular weight heparin]] administration, mechanical calf compression or (if all else is contraindicated and the patient has recently suffered deep vein thrombosis) the insertion of a [[Inferior vena cava filter|vena cava filter]].<ref>{{NICE|46|Venous thromboembolism (surgical)|April 2007}}</ref><ref name=ACCP>{{cite journal |author=Geerts WH, Pineo GF, Heit JA, ''et al'' |title=Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy |journal=Chest |volume=126 |issue=3 Suppl |pages=338S–400S |year=2004 |month=September |pmid=15383478 |doi=10.1378/chest.126.3_suppl.338S |url=http://www.chestjournal.org/cgi/content/full/126/3_suppl/338S}}</ref> In patients with medical rather than surgical illness, LMWH too is known to prevent thrombosis,<ref name=ACCP/><ref>{{cite journal |author=Dentali F, Douketis JD, Gianni M, Lim W, Crowther MA |title=Meta-analysis: anticoagulant prophylaxis to prevent symptomatic venous thromboembolism in hospitalized medical patients |journal=Ann. Intern. Med. |volume=146 |issue=4 |pages=278–88 |year=2007 |month=February |pmid=17310052 |url=http://www.annals.org/cgi/reprint/146/4/278.pdf |format=PDF}}</ref> and in the [[United Kingdom]] the [[Chief Medical Officer (United Kingdom)|Chief Medical Officer]] has issued guidance to the effect that preventative measures should be used in medical patients, in anticipation of formal guidelines.<ref name=Hunt/>
==See also==
* [[Anticoagulant]]s
==References==
{{reflist}}
==External links==
* [http://www.nattinfo.org/ National Alliance for Thrombosis and Thrombophilia] - National organization dedicated to thrombosis and thrombophilia.
{{Vascular diseases}}
[[Category:Hematology]]
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