Varicose veins of the lower extremities are usually caused by tortuous dilatation of the veins due to abnormal function of the venous valves. 1. Abnormal function of primary venous valves: Veins have valves that normally open only in one direction, so that the veins can prevent backflow of blood through the valves. However, varicose veins are often caused by damage to the valves or primary venous valve insufficiency, which results in blood pooling in the veins, which appears as swollen and tortuous veins. 2. Secondary venous valve dysfunction: In addition, after deep vein thromboembolism, superficial venous compensatory varicose veins may occur due to obstruction of deep vein return. 3. Others: Excessive body weight, female hormone secretion during pregnancy, arteriovenous fistula of the lower limbs, Bugart’s syndrome, etc. may also lead to superficial varicose veins of the lower limbs. If you have varicose veins, you need to actively consult the doctor and follow the doctor’s instructions for reasonable treatment.