Clinically, most patients do not pay much attention to the symptoms of sudden swelling and pain in the lower limbs. Unbeknownst to them, this is a typical manifestation of lower extremity deep vein thrombosis, which may lead to life-threatening pulmonary embolism if it is not treated in a timely and effective manner. If not treated in time and effectively, pulmonary embolism may occur, which may be life-threatening. In the later stage, deep vein obstruction or venous valve insufficiency in the lower limbs is often left behind, resulting in lower limb swelling and ulcers, which seriously affects the work and life. In the mid-nineteenth century, famous German pathologists have pointed out that the three major causes of lower extremity deep vein thrombosis (DVT) are: stagnant blood flow, damage to blood vessel walls, and hypercoagulability of blood components. Sedentary life and prolonged bed rest in the elderly, after trauma and surgery, as well as pregnancy and gestation, and after cerebral infarction and stroke are the main reasons for the development of this disease. In particular, the incidence of this disease increases with age. If a venous thrombus is dislodged, it can cause obstruction of the pulmonary artery and its branches, interrupting the blood flow to its corresponding blood-supplying lung tissues, and pulmonary embolism. The clinical manifestations of pulmonary embolism are varied and are actually a broader clinical spectrum. The main decision depends on the amount of vascular blockage, the speed of occurrence and the basic state of the heart and lungs, the light can be no symptoms; the more serious can appear cough, chest pain, difficulty in breathing, etc., serious shock or sudden death. Therefore, for patients with lower limb swelling, if the above symptoms occur, do not take them lightly, and should quickly go to the vascular surgery department.