Urine sodium

Urine sodium refers to the determination of sodium ion concentration in urine for 24 hours. There are 154 mmol of inorganic cations per liter of plasma, of which sodium ions account for about 90%, and almost half of the osmotic pressure of the plasma. Sodium plays a central role in maintaining normal water distribution and osmotic pressure. The kidney is the main organ that regulates sodium and water and maintains acid-base balance. Sodium is freely filtered by the kidneys, and most of it is reabsorbed. Excretion of urine sodium increases with the increase of blood sodium. The amount of sodium secreted by the human body at night is about one-fifth of the peak amount of sodium secreted during the day, indicating that the excretion of sodium has changed greatly within 1 day, so the measurement of urine sodium needs to retain all urine for 24 hours. Urinary sodium excretion is also closely related to dietary sodium and the body's water state.