Edema is the accumulation of excess water in the interstices of the body’s tissues resulting in swelling of the tissues. There are many causes of edema, which may be idiopathic, localized, or caused by diseases of the heart, liver, kidneys, and other organs. The main causes of edema are the following clear conditions: 1. Localized edema: As the name implies, edema occurs in a restricted part of the body (usually eyelids and lower extremities, symmetrical or asymmetrical), usually caused by problems such as varicose veins, cellulitis, venous embolism, and obstructed lymphatic return. This condition is very common in outpatients. 2. Systemic edema: (1) Renal disease: edema mostly occurs first in the tissue sparse areas, such as eyelids, face, and ankles, and is obvious in the morning with depressed acupressure, which can cause generalized edema, ascites, and pleural fluid in severe cases. It is usually accompanied by hematuria, proteinuria, hypertension, etc. Some patients also have abnormal kidney function. (2) Liver disease: ascites is the main cause. It may also first appear as edema in the foot and ankle and gradually spread upward, but the head, face and upper limbs are often free of edema. There is often a history of chronic liver disease. In addition to edema, clinical abnormalities of liver function such as decreased appetite, fatigue, aversion to oil and grease, and yellow sclera and skin staining are often associated. This is mainly seen in the advanced stage of various liver diseases, cirrhosis, and liver function decompensation. (3) Heart disease: Most of them have a history of heart disease, and before the appearance of edema, most of them already have manifestations of cardiac insufficiency such as feeling chest tightness and shortness of breath when walking or going up stairs, and inability to lie down at night. The edema first appears in the lower part of the body, and gradually spreads throughout the body from the lower extremities. No matter what kind of cardiac lesion is caused, as long as the heart function decreases, there will not be enough pressure to pump out the blood, resulting in stagnation of the body circulation, and the water in the blood will leak out from the blood vessels, thus causing edema. (4) Endocrine disorders: Abnormal thyroid function, primary aldosteronism, Cushing’s syndrome and other endocrine diseases may cause edema. In addition to edema, they are accompanied by manifestations of corresponding diseases and endocrine hormone abnormalities. (5) Edema caused by drugs: Some drugs may also cause edema, such as the familiar calcium antagonist antihypertensive drugs like nifedipine and loxoprogesterone, hormonal drugs, and traditional Chinese medicine containing licorice. If you take diet pills containing diuretics for a long time, once you stop taking them, they may also cause edema. (6) Malnutrition edema: Severe hypoproteinemia caused by excessive weight loss resulting in long-term protein intake and insufficient sodium and potassium intake, protein-losing gastrointestinal diseases, chronic wasting diseases, severe burns, etc. can cause sunken edema. (7) Idiopathic edema: The so-called idiopathic edema is edema without pathological factors. Such edema mostly occurs in the sagging parts of the body and is common in adult women, and may be related to endocrine disorders, menstrual cycle, mental changes, and long-term standing posture. Often lack of sleep, irregular life, lack of exercise, etc. can also cause edema. In summary, the etiology of edema is very complicated, and a comprehensive judgment must be made based on the location, degree, accompanying other symptoms and past medical history of the patient, and the necessary laboratory auxiliary tests must be performed.