Persistent urinary excretion of sodium belongs to the syndrome of abnormal secretion of antidiuretic hormone is a syndrome in which antidiuretic hormone continues to be secreted when plasma osmolality and blood sodium are normal or low, resulting in a series of clinical manifestations, such as decreased free water clearance, water retention, hyponatremia, and low osmolality blood pressure. What are the diagnostic criteria for persistent sodium excretion in urine? In addition to the manifestations of the original disease, children with SIADH are parallel to the degree of low blood sodium, serum sodium can be clinically asymptomatic when the serum sodium is above 120 mmol/L. When the blood sodium drops below 120 mmol/L, symptoms such as loss of appetite, nausea, vomiting can appear, and when the urinary sodium content is high and the blood sodium is below 110 mmol/L, neuropsychiatric symptoms, or even convulsions, coma until death, can be seen. When the blood sodium is lower than 95～109mmol/L, it can cause irreversible brain damage if it lasts for 3 days, so when hyponatremia occurs, it should be corrected in time. Diagnostic criteria are as follows: 1. Medical history often reveals a history of primary disease or medication. 2.Clinical manifestations have symptoms of hyponatremia. 3.High urinary sodium content, often >20mmol/L, low blood sodium <110mmol/L, or even up to 80mmol/L. 4.Higher than normal ADH in blood and urine measured by immunoassay. 5, Renal function and adrenocortical function are normal.