There are many causes of lower extremity edema, including functional and pathological edema and localized edema, and relevant tests need to be performed to identify the cause. Lower extremity edema, or edema, is a common symptom, which is seen in some functional edema caused by non-organic disease changes, and may also be pathological edema and local edema caused by certain diseases. 1. Functional edema: including edema caused by high temperature, edema caused by obesity, edema of old age, traveler’s edema, or sedentary edema. Functional edema is related to the environment in which a person lives and the physiological state of a person, so avoiding high temperature and sedentary edema will improve, and hospital consultation is not required. 2. Pathological edema: including cardiogenic edema mainly caused by right heart failure, nephrogenic edema caused by various nephritis and nephropathy, hepatogenic edema caused by cirrhosis, edema caused by endocrine metabolic abnormalities such as hypothyroidism, hyperthyroidism, Cushing’s syndrome, hypopituitarism, diabetes, etc., edema caused by pregnancy, edema caused by drugs, edema caused by premenstrual tension syndrome, etc. Edema caused by pregnancy, edema caused by medication, edema caused by PMS, etc. The cause of pathological edema should be discovered early and the primary disease should be treated early, and most of the edema will improve after the primary disease is treated. 3.Localized edema: inflammatory edema includes cellulitis, dermatitis, boils, carbuncles, high temperature and chemical burns; lymphatic reflux obstructive edema includes filariasis and lymphangitis; venous reflux obstructive edema includes venous thrombosis and varicose veins; angioneurotic edema, etc. Unlike the first two types of edema, local causes of edema tend to appear unilaterally and asymmetrically on both sides. Local edema should also be clarified early to identify the cause and treated symptomatically. There are many causes of lower extremity edema, which should not be generalized, but should be combined with other clinical manifestations and relevant laboratory tests and examinations to further clarify the cause, so as to provide symptomatic treatment.