The most common causes of swelling of both feet are prolonged standing, lower extremity venous thrombosis, kidney disease, heart failure and so on. 1. Standing for a long time: If the patient’s lower limbs stand for a long time, it is easy to cause poor reflux in the lower limbs, causing blood to gather locally and swelling, usually with sufficient rest and proper elevation of the lower limbs in the supine position, the swelling can disappear. 2. Lower extremity venous thrombosis: Due to various reasons, the lower extremities show high coagulation state, and eventually thrombosis occurs, which can appear as localized skin bruising, accompanied by obvious pain and swelling. 3. Kidney disease: If the patient has chronic nephritis or glomerulonephritis and other kidney diseases, swelling of both feet may occur. 4. Heart failure: patients with heart failure are prone to a relative decrease in the amount of return blood peripheral blood volume is relatively increased, also prone to swelling of the feet. Causes of swelling of both feet are more reasons, may also be associated with malnutrition, local inflammation, trauma and other reasons, if the symptoms continue without relief, it is recommended to promptly go to the hospital to find out the cause of the disease, by the doctor targeted treatment.