Venous thrombosis

A venous thrombosis is a blood clot that forms within a vein. (Thrombosis is a medical term for blood clotting (Haemostasis) occurring in the wrong place, i.e. a thrombus forming on the inside wall of a blood vessel.

Classification
Superficial venous thromboses can cause discomfort but generally do not cause serious consequences, unlike the deep venous thromboses (DVTs) that form in the deep veins of the legs or in the pelvic veins.

Since the veins return blood to the heart, if a piece of a blood clot formed in a vein breaks off it can be transported to the right side of the heart, and from there into the lungs. A piece of thrombus that is transported in this way is an embolism: the process of forming a thrombus that becomes embolic is called a thromboembolism. An embolism that lodges in the lungs is a pulmonary embolism (PE). A pulmonary embolus is a very serious condition that can be fatal if not recognized and treated promptly.

Systemic embolisms of venous origin can occur in patients with an atrial or ventricular septal defect, through which an embolus may pass into the arterial system. Such an event is termed a paradoxical embolism.

Risk factors

 * General
 * Older age
 * Female sex
 * Smoking
 * Obesity
 * Dehydration
 * Pregnancy
 * Immobilization
 * Minor injuries
 * Height, in men


 * Medical
 * Surgery
 * Trauma
 * Use of combined (containing both estrogen and progestin) forms of hormonal contraception
 * Varicose veins
 * Malignancy
 * Kidney disorders
 * Lupus anticoagulant
 * Paroxysmal nocturnal hemoglobinuria
 * Inflammatory bowel disease
 * Thromboangiitis obliterans (Mb Bürger)
 * Disseminated intravascular coagulation


 * Familial
 * Antithrombin III deficiency
 * Protein C deficiency/Protein S deficiency
 * APC resistance (Factor V Leiden)
 * Dysfibrogenemia
 * Hypoplasminogenemia
 * Familial hyperhomocysteinemia

Prevention and treatment
Evidence-based guidelines have been published for the treatment and prevention of venous thromboembolism. Recommendations include mechanical thromboprophylaxis methods and devices such as frequent ambulation, intermittent pneumatic compression and specially-designed compression stockings. Medications used to treat and prevent this condition include anticoagulants such as heparin, fondaparinux and more recently dabigatran has shown promise. Vitamin K antagonists such as warfarin are also commonly used. Vitamin E may prevent venous thrombosis.