First of all, we should exclude the edema caused by renal disease, the edema caused by renal disease usually occurs in the eyelids or face, or ankles, obvious in the morning, when serious, it can involve the edema of the lower limbs, and there will be non-disappearance of foam during urination, this kind of patients may also have high blood pressure and reduced urine output, and the blood creatinine may be elevated in the laboratory test. It is also necessary to exclude edema caused by heart disease, edema in heart failure usually starts from the feet and lower limbs first, and will be depressed when pressed, and laboratory tests may find that the heart and liver are large, and some patients will have obvious breath-holding. There is also the need to exclude endocrine-induced edema, such as hypothyroidism, can also appear edema, mainly calves and orbits have obvious swelling, when pressed will seldom have depression, there will be no pleural fluid and ascites, this type of patients are afraid of cold, slow reaction, there is constipation or diarrhea, easy to sweat, and there will be abnormalities in the function of the thyroid gland. Cirrhosis, malnutrition, the late occurrence of edema will involve the lower limbs, go to the hospital to do a specialized examination, basically can identify the cause.