The causes of edema are divided into systemic and localized edema. The main causes of systemic edema, are the following: i. Cardiogenic edema, mainly due to the cause of right heart failure. Renal edema, which can be seen in all types of nephritis and nephropathy. Hepatogenic edema, cirrhosis of the liver is the most common cause of hepatogenic edema, mainly manifested as ascites, can also first appear ankle edema, gradually spread to the whole body. Edema caused by endocrine metabolic diseases, mainly hypothyroidism, hyperthyroidism, primary aldosteronism, Cushing’s syndrome, pituitary hypoplasia and diabetes mellitus. Fifth, malnutrition edema, is due to chronic disease long-term nutritional deficiency, protein loss. Sixth, gestational edema. Most women have edema in the second trimester of pregnancy, most of which is physiological, most of which subsides spontaneously after delivery, and some of which is pathologic. Edema caused by connective tissue diseases. Metabolic edema. Edema caused by drugs. Premenstrual tension syndrome. XI. Idiopathic edema, which is of unknown cause and may be related to endocrine disorders. XII. Functional edema, which has no organic pathology but is due to factors such as environment, constitution, and body position. Common causes of localized edema include inflammatory edema, lymphatic reflux disordered edema, venous reflux disordered edema, angioneurotic water, neurogenic edema, and localized mucous edema.