The cause of swollen legs and feet, first of all, should be distinguished whether both legs and feet swell at the same time, or one side of the leg and foot swelling phenomenon. If swelling occurs in one leg or foot, it may be due to the formation of deep vein thrombosis in the lower extremity or incomplete closure of the venous valves, which can cause stagnation of venous blood, especially in the legs. The legs are in the lowest position of the body, so they are most likely to be swollen. It is also possible to have swollen legs and feet bilaterally due to Bu-ga syndrome, right heart insufficiency, pulmonary hypertension, cardiac insufficiency, liver insufficiency, and renal insufficiency. Therefore, when swelling of the legs and feet occurs, it is necessary to take a medical history, and to examine the patient and perform some auxiliary tests to clarify the diagnosis.