One leg edema, one leg not swollen to consider three aspects of the problem: First, the leg vascular problems, of course, the leg vascular problems are divided into two cases: the first case, leg vein problems, under normal circumstances the veins will transport the rest of the body’s blood back to the heart, but if the venous valve function is abnormal, the veins are unable to send a sufficient amount of blood back to the heart, can cause calf edema. In the second case, thrombotic problems, blood clots blocking the veins in the legs can cause leg edema. Second, lymphedema, lymphedema is leg edema caused by having congenital lymphatic duct hypoplasia, or acquired disease that causes blockage of lymphatic fluid channels, making lymphatic return obstruction. Third, stroke, some stroke patients with long-term inactivity of one side of the limb will lead to impaired blood circulation, which will also appear edema. If one leg is swollen and one leg is not, you can check the leg ultrasound to see if there is any problem through relevant examination.