Thrombus (clot) may form in the veins causing a condition called venous thrombosis. Depending on the size and location of the thrombus and the reasons for the thrombus, the symptoms may range from minor discomfort to severe pain and even death. Thrombus breaking loose from the site of its development and moving with blood flow through the heart to the lung is a process called pulmonary embolism. Pulmonary embolism may cause unexplained shortness of breath or chest pain and may block-blood flow through the lungs resulting in sudden death. Some patients have inherited clotting disorders or may be more prone to clots due to other medical conditions, injuries, or surgery.
Inherited disorders or gene mutations may cause clotting of deep or superficial veins, often occurring when some other event increases the risk of clotting. Some of these include:
Factor V Leiden mutation,
Prothrombin gene mutation,
Antithrombin III deficiency,
Protein S deficiency,
Protein C deficiency.
Other clotting disorders may develop due to other medical conditions such as lupus erythematosis with “lupus anticoagulant” which actually is a condition increasing the risk of clotting. Cancers increase the risk of venous thrombosis as do prolonged sitting or bed-rest, major injuries, and many surgical procedures. Smoking and hormonal medications, especially oral contraceptives, increase the risk of venous thrombosis.
Superficial Venous Thrombosis (SVT)
Clot forming in the veins of the skin or fatty tissues of the extremities is called superficial venous thrombosis (SVT). Symptoms often involve a tender lump under the skin at the location of a vein with a pink color in the skin overlying the thrombus. Superficial thrombus rarely is life-threatening since it usually forms in veins which are small. Any thrombus which migrates from small veins in the circulation is unlikely to significantly block flow in the veins of the lungs. However, 20% of patients who develop SVT will also be found to have extension of the thrombus into the deep veins of the extremity (DVT) which is a much more serious condition. For this reason, venous color duplex ultrasound examinations frequently are employed to evaluate the extent of the thrombus.
Deep Venous Thrombosis (DVT)
The deep veins of the extremities are the veins within the muscles. Deep vein thrombosis (DVT), clotting in the veins of the extremity muscles or in the pelvis, abdomen, or chest is a serious condition which can lead to major disability or death if the thrombus is extensive and obstructs venous blood flow through enough tissue or migrates to the lungs and obstructs flow (pulmonary embolism).
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