Swelling of the legs of an 84-year-old woman can be seen in diseases such as poor venous return of the lower limbs, cardiovascular disease and renal disease. 1. Poor venous return of the lower limbs: Older people are less active and like to be sedentary. The lower limbs are in a prolonged sagging state, which is easy to have poor venous return of the lower limbs and cause leg swelling. 2. Cardiovascular disease: elderly patients who have underlying cardiovascular disease, such as previous myocardial infarction, coronary heart disease, cardiac insufficiency, can cause heart failure. In right heart failure, the right heart pumping ability decreases, blood accumulates, resulting in decreased blood return to the peripheral veins, and edema in the leg area will be observed. 3. Kidney diseases: such as renal insufficiency and nephrotic syndrome. When hypoproteinemia occurs, due to the decrease of plasma colloid osmotic pressure, tissue fluid is constantly gathering in the interstitial space of tissues, and edema of the lower limbs appears. In addition to the above, leg swelling in an 84-year-old woman can be seen for other reasons. It is recommended to consult a doctor for further examination, to clarify the cause with the help of the doctor, and to actively cooperate with the doctor in handling or treating the problem.