The swelling of the feet in the elderly can be due to a variety of causes, and is generally common for the following reasons: 1. heart failure, patients have swelling of the feet in addition to panic, chest tightness, chest pain, wheezing, dyspnea, etc. 2. renal failure, patients have swelling of the feet in addition to edema of the face and eyelids, which may be accompanied by proteinuria, hematuria, anemia, weakness, nadir, nausea, etc. 3. hypoproteinemia. In addition to swelling of both lower extremities, patients may also have edema of multiple parts of the body with hypoproteinemia. 4. Hypothyroidism, in addition to swelling of both feet, patients may also have edema of multiple parts of the body with a non-depressed nature. Ultrasound can reveal atherosclerosis or even deep vein thrombosis, and the edema can be localized with redness, swelling, heat and pain.