Diatriacal regurgitation in children may be a normal physiologic phenomenon, or it may be caused by related diseases, which can be categorized into acquired and congenital. 1. Physiological phenomenon: In infants and young children under three years of age, if there is mild regurgitation of the mitral valve, it is most likely a physiological phenomenon, which does not affect cardiac function and the normal growth and development of children. 2. Acquired diseases: Common diseases include rheumatic heart disease and infective endocarditis. Rheumatic heart disease is a heart valve disease caused by rheumatic fever activity, which involves the heart valves; infective endocarditis is an acute or subacute endocardial inflammation mostly caused by bacteria or fungi, etc., which may lead to valve damage. 3. Congenital diseases: Some congenital structural malformations of the heart and other connective tissue diseases such as Marfan’s syndrome may also lead to diatriacal valve. It is recommended to visit a specialized hospital to identify the cause of the disease and follow the doctor’s instructions.