Unusual swelling, pain, and varicose veins in the lower extremities can be caused by venous thrombosis. This article will tell you about the blood case caused by the “running thrombus”. 1, the formation of deep vein thrombosis: when blood clots are formed in the veins of the leg muscles, there is a venous thrombosis (DVT). Normally, it is helpful when the blood clots to block the wound to prevent life-threatening bleeding. However, sometimes this clot formation process (also called coagulation) can be improperly triggered, forming clots in the venous vessels when they are not needed to stop bleeding. Common risk factors that predispose to such conditions include surgery, tumors, braking, obesity, smoking, pregnancy, family history, and the effects of medications. 2, symptoms of deep vein thrombosis: most of the deep vein thrombosis has insidious nature and no obvious symptoms, a few patients can have symptomatic deep vein thrombosis. The symptoms are one or more of the following: (1) sudden swelling, hardness, pain and abnormal touch of the affected limb (aggravated by activity, reduced by elevating the affected limb, and often accompanied by pressure pain at the site of venous thrombosis); (2) unilateral (or bilateral, mostly left lower limb), hip, lower abdomen or external genital edema of the lower limb; (3) elevated skin temperature. 3. Dangers of deep vein thrombosis: Regardless of the trigger, deep vein thrombosis can become large enough to block blood flow like a dam, leading to the typical symptoms of swelling as well as pain. A more serious consequence is the result of pulmonary embolism and also the possibility of post-thrombotic syndrome. Some or all of the blood clots shed by a pulmonary embolism may travel with the blood flow through the heart to the lungs, blocking the blood vessels in the lungs and causing respiratory dysfunction, resulting in a potentially fatal condition called “pulmonary embolism (PE)”. ”Pulmonary embolism (PE) can be fatal, so it is important to be alert to the symptoms of PE, which include shortness of breath, chest pain, coughing up blood, and a rapid heartbeat. Studies have shown that nearly 50% of proximal DVTs progress to PE, and 79% of pulmonary embolism patients have a combination of DVT in the lower extremities, which is why it is so important to treat DVT quickly and effectively so that you have strong protection against DVT and PE recurrence. Post-thrombotic syndrome (PTS) can occur in the chronic phase of DVT with an incidence of 20% to 50%. The main symptoms are swelling and pain in the lower extremities (the severity of which varies with time). Signs include lower extremity edema, hyperpigmentation, eczema, varicose veins, and in severe cases, lipodermatous scleroderma and ulcers in the foot and boot area.