Deep vein thrombosis

Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis.

Using blood thinners is the standard treatment. Typical medications include rivaroxaban, apixaban, and warfarin. Beginning warfarin treatment requires an additional non-oral anticoagulant, often injections of heparin. though they can develop suddenly or over a matter of weeks. The legs are primarily affected, with 4–10% of DVT occurring in the arms. In those who are able to walk, DVT can reduce one's ability to do so. The pain can be described as throbbing and can worsen with weight-bearing, prompting one to bear more weight with the unaffected leg.

Additional signs and symptoms include tenderness, pitting edema (see image), dilation of surface veins, warmth, discoloration, a "pulling sensation", and even cyanosis (a blue or purplish discoloration) with fever. Rarely, a clot in the inferior vena cava can cause both legs to swell. Superficial vein thrombosis, also known as superficial thrombophlebitis, is the formation of a blood clot (thrombus) in a vein close to the skin. It can co-occur with DVT and can be felt as a "palpable cord".

Potential complications

A pulmonary embolism (PE) occurs when a blood clot from a deep vein (a DVT) detaches from a vein (embolizes), travels through the right side of the heart, and becomes lodged as an embolus in a pulmonary artery that supplies deoxygenated blood to the lungs for oxygenation. and can vary based upon where the embolus is lodged in the lungs. An estimated 30–50% of those with PE have detectable DVT by compression ultrasound. It is life-threatening, limb-threatening, and carries a risk of venous gangrene. Phlegmasia cerulea dolens can occur in the arm but more commonly affects the leg. If found in the setting of acute compartment syndrome, an urgent fasciotomy is warranted to protect the limb. Superior vena cava syndrome is a rare complication of arm DVT.

File:SaddlePE.PNG|alt=A computed tomography image depicting PE in the pulmonary arteries|A CT image with red arrows indicating PE (grey) in the pulmonary arteries (white)

File:PCD2016.jpg|alt=Image showing marked discoloration of a leg with phlegmasia cerulea dolens|A case of phlegmasia cerulea dolens in the left leg

Patent-foramen-ovale-en.png|alt=A drawing depicting a patent foramen ovale|A depiction of a patent foramen ovale

</gallery>

Differential diagnosis

In most suspected cases, DVT is ruled out after evaluation. Cellulitis is a frequent mimic of DVT, with its triad of pain, swelling, and redness. superficial vein thrombosis, muscle vein thrombosis, and varicose veins.

Classification

thumb|upright=1.4|The iliac veins (in the pelvis) include the external iliac vein, the internal iliac vein, and the common iliac vein. The common femoral vein is below the external iliac vein. (It is labeled simply "femoral" here.)|alt=Drawing showing that moving down the body, the inferior vena cava branches into 2 common iliac veins. The common iliac veins split into the internal iliac and external iliac veins. The external iliac veins give rise to the common femoral veins.

DVT and PE are the two manifestations of the cardiovascular disease venous thromboembolism (VTE).

DVT is classified as acute when the clots are developing or have recently developed, whereas chronic DVT persists for more than 28 days. An episode of VTE after an initial one is classified as recurrent. Bilateral DVT refers to clots in both limbs while unilateral means only a single limb is affected.

DVT in a leg above the knee is termed proximal DVT (proximal). DVT in a leg below the knee is termed distal DVT (distal), also called calf DVT when affecting the calf, and has limited clinical significance compared to proximal DVT. Calf DVT makes up about half of DVTs. Iliofemoral DVT is described as involving either the iliac, or common femoral vein; elsewhere, it has been defined as involving at a minimum the common iliac vein, which is near the top of the pelvis.

DVT can be classified as provoked and unprovoked. The distinction between these categories is not always clear.

Causes

thumb|left|Depiction of DVT|alt=Artistic rendering of DVT

Traditionally, the three factors of Virchow's triad—venous stasis, hypercoagulability, and changes in the endothelial blood vessel lining—contribute to VTE and were used to explain its formation. More recently, inflammation has been identified as playing a clear causal role. Other related causes include activation of immune system components, the state of microparticles in the blood, the concentration of oxygen, and possible platelet activation. Previous VTE, particularly unprovoked VTE, is a strong risk factor. Major surgery and trauma increase risk because of tissue factor from outside the vascular system entering the blood. hip fracture, and long bone fractures are also risks. paralysis, sitting, long-haul travel, bed rest, hospitalization, catatonia, and in survivors of acute stroke. Conditions that involve compromised blood flow in the veins are May–Thurner syndrome, where a vein of the pelvis is compressed, and venous thoracic outlet syndrome, which includes Paget–Schroetter syndrome, where compression occurs near the base of the neck.

Infections, including sepsis, COVID-19, HIV, and active tuberculosis, increase risk. Chronic inflammatory diseases and some autoimmune diseases, such as inflammatory bowel disease, systemic sclerosis, Behçet's syndrome, primary antiphospholipid syndrome, increase risk. SLE itself is frequently associated with secondary antiphospholipid syndrome.

Cancer can grow in and around veins, causing venous stasis. It can also stimulate higher levels of tissue factor. Cancers of the blood, lung, pancreas, brain, stomach, and bowel are associated with high VTE risk. Solid tumors such as adenocarcinomas can contribute to both VTE and disseminated intravascular coagulation. In severe cases, this can lead to simultaneous clotting and bleeding. Chemotherapy treatment also increases risk. Obesity increases the potential of blood to clot, as does pregnancy. In the postpartum, placental tearing releases substances that favor clotting. Oral contraceptives and hormonal replacement therapy increase the risk through various mechanisms, including altered blood coagulation protein levels and reduced fibrinolysis.

thumb|350px|The [[coagulation system, often described as a "cascade", includes a group of proteins that regulate clotting. Abnormalities in the cascade can alter the risk of DVT. The regulators, antithrombin (ᾳTHR) and activated protein C (APC), are shown in green above the clotting factors they affect.|alt=Imagine showing the coagulation, which includes a group of proteins that regulate clotting. Abnormalities in the cascade can alter the risk of DVT.]]

Dozens of genetic risk factors have been identified, mildly increases VTE risk by about three times. Having a non-O blood type roughly doubles VTE risk. Individuals without O blood type have higher blood levels of von Willebrand factor and factor VIII than those with O blood type, increasing the likelihood of clotting. The genetic variant prothrombin G20210A, which increases prothrombin levels, hyperhomocysteinemia, paroxysmal nocturnal hemoglobinuria, nephrotic syndrome, chronic kidney disease, polycythemia vera, essential thrombocythemia, intravenous drug use, and smoking.

Some risk factors influence the location of DVT within the body. In isolated distal DVT, the profile of risk factors appears distinct from proximal DVT. Transient factors, such as surgery and immobilization, appear to dominate, whereas thrombophilias and age do not seem to increase risk. Common risk factors for having an upper extremity DVT include having an existing foreign body (such as a central venous catheter, a pacemaker, or a triple-lumen PICC line), cancer, and recent surgery.

Pathophysiology

thumb|500px

Blood has a natural tendency to clot when blood vessels are damaged (hemostasis) to minimize blood loss. Clotting is activated by the coagulation cascade, and the clearing of clots that are no longer needed is accomplished by the process of fibrinolysis. Reductions in fibrinolysis or increases in coagulation can increase the risk of DVT. DVT most frequently affects veins in the leg or pelvis including the popliteal vein (behind the knee), femoral vein (of the thigh), and iliac veins of the pelvis. Extensive lower-extremity DVT can even reach into the inferior vena cava (in the abdomen). Upper extremity DVT most commonly affects the subclavian, axillary, and jugular veins. This is the preferred process. Aside from the potentially deadly embolization process, a clot can resolve through organization, which can damage venous valves, cause venous fibrosis, and result in non-compliant veins.

thumb|350px|left|Upper extremity DVTs can occur in the subclavian, axillary, brachial, ulnar, and radial veins (pictured) and the [[Jugular vein|jugular and brachiocephalic veins (not pictured). The cephalic and basilic veins, however, are superficial. but clotting in the veins mostly occurs without any such mechanical damage. NETs provide "a scaffold for adhesion" of platelets, red blood cells, and multiple factors that potentiate platelet activation. In addition to the pro-coagulant activities of neutrophils, multiple stimuli cause monocytes to release tissue factor. Monocytes are also recruited early in the process. Hospitalized patients often have elevated levels for multiple reasons.

==Diagnosis==

A clinical probability assessment using the Wells score (see column in the table below) to determine if a potential DVT is "likely" or "unlikely" is typically the first step of the diagnostic process. The score is used in suspected first lower extremity DVT (without any PE symptoms) in primary care and outpatient settings, including the emergency department. it does have drawbacks. The Wells score requires a subjective assessment regarding the likelihood of an alternate diagnosis and performs less well in the elderly and those with a prior DVT. The Dutch Primary Care Rule has also been validated for use. It contains only objective criteria but requires obtaining a D-dimer value. With this prediction rule, three points or less means a person is at low risk for DVT. A result of four or more points indicates an ultrasound is needed. Three compression ultrasound scanning techniques can be used, with two of the three methods requiring a second ultrasound some days later to rule out the diagnosis. Whole-leg ultrasound is the option that does not require a repeat ultrasound, Ultrasound methods including duplex and color flow Doppler can be used to characterize the clot further) distal to the branching point of the deep femoral vein. When compared to this clot, clots that instead obstruct the common femoral vein (proximal to this branching point) cause more severe effects due to impacting a significantly larger portion of the leg.

File:Iliac vein deep vein thrombosis.JPEG|An abdominal CT scan demonstrating an iliofemoral DVT, with the clot in the right common iliac vein of the pelvis

File:Vascular anatomy lower extremity for DVT POCUS.png|Vascular anatomy for deep venous thrombosis (DVT) point of care ultrasound (POCUS)

</gallery>

Management

Treatment for DVT is warranted when the clots are either proximal, distal, and symptomatic, or upper extremity and symptomatic. Providing anticoagulation, or blood-thinning medicine, is the typical treatment after patients are checked to make sure they are not subject to bleeding. However, treatment varies depending upon the location of DVT. For example, in cases of isolated distal DVT, ultrasound surveillance (a second ultrasound after 2 weeks to check for proximal clots), might be used instead of anticoagulation. Although, those with isolated distal DVT at a high risk of VTE recurrence are typically anticoagulated as if they had proximal DVT. Those at low risk of recurrence might receive a four- to six-week course of anticoagulation, lower doses, or no anticoagulation at all. together with warfarin is given, which is followed by warfarin-only therapy. of 2.0–3.0, with 2.5 as the target. The benefit of taking warfarin declines as the duration of treatment extends, and the risk of bleeding increases with age. Periodic INR monitoring is not necessary when first-line direct oral anticoagulants are used. Overall, anticoagulation therapy is complex, and many circumstances can affect how these therapies are managed.

The duration of anticoagulation therapy (whether it will last 4 to 6 weeks, When proximal DVT is provoked by surgery or trauma a 3-month course of anticoagulation is standard. Those who finish warfarin treatment after idiopathic VTE with an elevated D-dimer level show an increased risk of recurrent VTE (about 9% vs about 4% for normal results), and this result might be used in clinical decision making. Thrombophilia test results rarely play a role in the length of treatment.

Treatment for acute leg DVT is suggested to continue at home for uncomplicated DVT instead of hospitalization. Factors that favor hospitalization include severe symptoms or additional medical issues. Early walking is suggested over bedrest. Graduated compression stockings—which apply higher pressure at the ankles and a lower pressure around the knees as the potential benefit of using them for this goal "may be uncertain". They are, however, recommended in those with isolated distal DVT. It is only about 33% as effective as anticoagulation in preventing recurrent VTE.

Investigations for cancer

An unprovoked VTE might signal the presence of an unknown cancer, as it is an underlying condition in up to 10% of unprovoked cases. It is not recommended practice to obtain tumor markers or a CT of the abdomen and pelvis in asymptomatic individuals. have not established a net benefit in those with acute proximal DVT. Drawbacks of catheter-directed thrombolysis (the preferred method of administering the clot-busting enzyme Catheter-directed thrombolysis with thrombectomy Phlegmasia cerulea dolens might be treated with catheter-directed thrombolysis and/or thrombectomy.

File:Gray966.png|The first rib, which is removed in a first rib resection surgery, is labeled 1 in this image

File:A-case-of-Paget-Schroetter-syndrome-(PSS)-in-a-young-judo-tutor-a-case-report-13256 2016 848 Fig1 HTML.jpg|A venogram before catheter-directed thrombolysis for Paget–Schroetter syndrome, a rare and severe arm DVT shown here in a judo practitioner, with highly restricted blood flow shown in the vein

File:A-case-of-Paget-Schroetter-syndrome-(PSS)-in-a-young-judo-tutor-a-case-report-13256 2016 848 Fig2 HTML.jpg|After treatment with catheter-directed thrombolysis, blood flow in the axillary and subclavian vein was significantly improved. Afterwards, a first rib resection allowed decompression. This reduces the risk of recurrent DVT and other sequelae from thoracic outlet compression. Other studies including a systematic review and meta-analysis did not find a difference in mortality with IVC placement. If someone develops a PE despite being anticoagulated, care should be given to optimize anticoagulation treatment and address other related concerns before considering IVC filter placement. Patients suspected of having an acute DVT are often referred to the emergency department for evaluation. Interventional radiology is the specialty that typically places and retrieves IVC filters, and vascular surgery might do catheter directed thrombosis for some severe DVTs. Walking increases blood flow through the leg veins. Excess body weight is modifiable, unlike most risk factors, and interventions or lifestyle modifications that help someone who is overweight or obese lose weight reduce DVT risk. Statins have been investigated for primary prevention (prevention of a first VTE), and the JUPITER trial, which used rosuvastatin, has provided some tentative evidence of effectiveness. Of the statins, rosuvastatin appears to be the only one with the potential to reduce VTE risk. If so, it appears to reduce risk by about 15%.

Hospital (non-surgical) patients

Acutely ill hospitalized patients are suggested to receive a parenteral anticoagulant, although the potential net benefit is uncertain.