Persistent sodium excretion in urine

Introduction Sustained sodium excretion in the urine belongs to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). When the plasma osmotic concentration and normal or low blood sodium are normal, the vasopressin is still secreted, resulting in free water clearance. A syndrome of a series of clinical manifestations such as hypotension, water retention, hyponatremia, and low osmolality. In addition to the primary disease manifestations, SIADH children are parallel with the degree of hyponatremia. When serum sodium is above 120mmol/L, the clinical symptoms are asymptomatic. When the blood sodium drops below 120mmol/L, there may be loss of appetite and nausea. Symptoms such as vomiting, when the urine sodium content is high, blood sodium is lower than 110mmol / L, neuropsychiatric symptoms, even convulsions, coma until death, when blood sodium is lower than 95 ~ 109mmol / L, for 3 days can cause irreversible Brain damage, so when hyponatremia occurs, it should be corrected in time.

Cause

(1) Causes of the disease

The cause of SIADH may be increased secretion of non-endocrine atopic ADH, or ADH regulatory dysfunction, such as lung disease (pneumonia, tuberculosis, asthma persistent state); central nervous system diseases (meningitis, encephalitis, brain abscess, brain Tumors, brain trauma, acute infectious radiculitis, subarachnoid hemorrhage and cerebrovascular disease can produce ADH-like substances. In addition, during hypoxemia, the cardiac output decreases, which can also stimulate the secretion of ADH. Malignant tumors such as lung cancer, duodenal cancer, pancreatic cancer, prostate cancer, thymic cancer, etc. These tumor cells can produce ADH, which is a heterologous hormone secreting tumor. This condition is rare in children, and some drugs such as chlorpropamide Vincristine, clofibrate (clofibrate) and thiazides can increase renal tubular sensitivity to ADH or to neurons in the hypothalamus, increasing ADH secretion, as well as SIADH, neonatal asphyxia, Intracranial hemorrhage can cause this disease.

(two) pathogenesis

Due to increased secretion of ADH, renal tubular absorption of water, body water retention, increased body fluid volume and dilute hyponatremia, in order to maintain intracellular and extracellular osmotic pressure balance, water enters the cell, causing intracellular edema, especially brain cell edema is more obvious The disease has low blood sodium, but high urinary sodium, high osmotic urinary pressure, and urinary osmotic pressure exceeds blood osmotic pressure. The cause of high urinary sodium is related to the reduction of sodium absorption by the renal tubule and the inhibition of aldosterone secretion. It is also associated with an increase in sodium-sparing factors and prostaglandins.

an examination

Related inspection

Urine routine renal function test

The diagnostic criteria are as follows:

1. History: There is a history of primary disease or medication.

2. Clinical manifestations: symptoms of hyponatremia.

3. Urine sodium: high content, often >20mmol/L, low blood sodium <110mmol/L, even up to 80mmol/L.

4. Radioimmunoassay: ADH in blood and urine is higher than normal.

5. Renal function and adrenal cortical function are normal.

Differential diagnosis

SIADH should be differentiated from other causes of hyponatremia. Such as kidney disease, liver and heart disease caused by hyponatremia, in addition to disease-related symptoms, there may be edema, aldosterone increased, urine sodium decreased. Low blood sodium and high urine sodium caused by chronic adrenal function reduction. The clinical features are skin pigmentation, which can be identified by urine and blood cortisol assays.

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