Persistent sodium excretion in urine belongs to the syndrome of abnormal antidiuretic hormone secretion, which refers to a series of clinical manifestations such as reduced free water clearance, water retention, hyponatremia, and low osmotic blood pressure when plasma osmolality and blood sodium are normal or low, but antidiuretic hormone is still continuously secreted. What are the reasons for the occurrence of persistent sodium excretion in urine? The cause of SIADH can be non-endocrine ectopic ADH secretion or ADH regulation disorder, such as lung disease; central nervous system diseases can produce ADH-like substances, in addition, in hypoxemia, the heart beat output decreases, which can also stimulate the secretion of ADH, some malignant tumors such as lung cancer, duodenal cancer, pancreatic cancer, prostate cancer, thymic cancer, etc., these tumor cells can produce Some malignant tumors such as lung cancer, duodenal cancer, pancreatic cancer, prostate cancer, thoracic cancer, etc., these tumor cells can produce ADH, which is a heterologous hormone-secreting tumor, and this condition is rare in pediatric patients. Due to increased secretion of ADH, increased water absorption by renal tubules, water retention in the body, increased fluid volume and dilutional hyponatremia, in order to maintain the balance of osmotic pressure inside and outside the cells, water enters the cells, causing intracellular edema, especially brain cell edema is more obvious, the disease is characterized by low blood sodium, but high urinary sodium, high osmotic pressure urine, urinary osmolality exceeds blood osmolality, causing high urinary sodium in addition to the causes of sodium absorption by renal tubules, decreased aldosterone secretion, and decreased sodium absorption by renal tubules. In addition to reduced sodium absorption by the renal tubules and inhibition of aldosterone secretion, it is also associated with increased sodium excretion factors and prostaglandins. When the serum sodium is above 120 mmol/L, the clinical symptoms may be asymptomatic. When the blood sodium drops below 120 mmol/L, symptoms such as loss of appetite, nausea and vomiting may appear. When the blood sodium is lower than 95-109mmol/L for 3 days, it can cause irreversible brain damage, so when hyponatremia occurs, it should be corrected in time.