What Is Urine Osmolality?

Osmotic pressure refers to a water absorption force of solute molecules through a semi-permeable membrane, and its size depends on the number of solute particles, and has nothing to do with the molecular weight and radius of the solute. Urine osmolarity, also known as urine osmolality, urine osmolality, refers to the total number of microparticles excreted by the kidney from all solutes, such as electrolytes, urea, sugars, and proteins. The kidneys regulate the balance of body fluid penetration by concentrating or diluting urine. The normal person's plasma osmotic pressure is 280-310mOsm / kg · H20, and the normal person's urine osmotic pressure / plasma osmotic pressure ratio is (3 ~ 4.5): 1. This indicator is also used to evaluate the kidney's concentrated dilution function. Urine osmotic pressure at 300mOsm / kg · H20 is called isotonic urine, higher than plasma osmotic pressure indicates that urine has been concentrated, at this time it can be called hypertonic urine; below plasma osmotic pressure indicates that urine has been diluted, this The urine at this time is called hypotonic urine. Urine osmotic concentration reflects the relative excretion rate of solute and water by the kidney, and is not affected by the size and properties of solute particles, but only by the number of solute particles. Urine osmolality measurement can more accurately reflect the renal concentration function than urine relative density measurement. The commonly used method for measuring urine osmotic pressure is the freezing point method.

Basic Information

Chinese name

Urine osmotic pressure

Meaning

Reflects the kidney's concentrated dilution function

Clinical significance of urine osmotic pressure

Urine osmotic pressure can reflect the concentrated dilution function of the kidney, and is often used in conjunction with plasma osmolality measurement.

1. Elevation: seen in high fever, dehydration, cardiac insufficiency, acute nephritis, poor peripheral circulation, diarrhea, renal congestion, etc.

2. Decrease: It is found in diseases with severely impaired renal condensing function, such as chronic pyelonephritis, polycystic kidney disease, chronic renal failure, diabetes insipidus, urinary obstructive nephropathy, uric acid nephropathy, acute tubular dysfunction and the Primary glomerular disease.

Reference range of normal urine osmolality

> 600mOsm / kg · H ₂ O