Edema (edema) refers to excessive sodium and water retention in the tissue spaces outside the blood vessels and is one of the common clinical symptoms. Unlike obesity, edema is manifested as a distinct depression when fingers are pressed on areas with little subcutaneous tissue (e.g., at the ankle), and the skin is removed when fingers are held away. Systemic edema can be classified according to the etiology: (1) Cardiogenic edema: It is often symmetrical, starting from the ankle and gradually rising to involve the calf, thigh, genitalia and abdominal wall. When the patient is bedridden for a long time, it is mostly confined to the sacrococcygeal region. It is commonly seen in bruising heart failure and pericarditis. (2) Nephrogenic edema: common in glomerulonephritis, pyelonephritis and nephrotic syndrome, etc. (3) Hepatogenic edema: first manifested as abdominal edema. Commonly seen in viral hepatitis, cirrhosis, etc. (4) Malnutrition edema: commonly seen in hypoproteinemia, vitamin Bl deficiency, etc. Edema in children with precocious heart disease can also be caused by this, such as intestinal-derived protein loss after Fontan surgery. (5) Edema due to connective tissue disease: common in lupus erythematosus, scleroderma, and dermatomyositis, etc. (6) Allergic edema: such as serum sickness. (7) Endocrine edema: common in Silhan’s disease, hypothyroidism and Cushing’s syndrome, etc. (8) Idiopathic edema: such as functional edema, etc. (9) Drugs: Drug-induced edema is caused by the use of anti-inflammatory and analgesic agents that affect the excretory function of the kidneys, or steroid preparations “American Elixir” that harm the adrenal function. Others include anemic edema and toxic edema of pregnancy. Restricted edema includes: (1) venous obstructive edema: common in thrombophlebitis, varicose veins of the lower extremities, etc. (2) Lymphatic obstructive edema: commonly seen in elephantiasis of filariasis, chest edema due to mumps, etc. (3) Inflammatory edema: common in local edema caused by dengue, boils, cellulitis, etc. (4) Reactive edema: common in angioneurotic edema, contact dermatitis, etc.