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Test Code OSMOU Osmolality Urine

Additional Codes

Cerner

NextGen

Osmolality Urine

Osmolality Urine

Useful For

Osmosis is the process that constitutes the movement of solvent across a membrane in response to differences in osmotic pressure across the membrane.  Water migrates across the membrane toward the side containing more concentrated solute. The osmolality of body fluids may be measured in serum or urine.  The osmotic pressure is maintained by the charged solutes in the plasma, i.e., sodium, potassium, iron, bicarbonate, chloride, protein, etc.  The osmotic pressure must be maintained within fairly narrow range in the water compartments of the body. If the pressure becomes too high, it can result in pressure on the brain and brainstem; too low pressure tends to decrease the structural integrity of solid tissues.  The regulation of the osmolality is controlled by thirst and ADH function in the renal tubules.

Methodology

Freezing point depression

Patient Preparation

None

Collection Instructions

  • Catheterized specimens collected according to clinical policies and procedures
  • Radom clean catch instructions: Random Urine Collection Instructions
  • Keep samples capped to avoid evaporation.

Specimen Requirements

Container

  • Sterile/clean plastic urine container

 or  or

  • Non-preservative urine tube (BD Vacutainer® Ref #364980)

Stability

Storage

Temperature

Stability

Room Temperature

18-28°C

≤ 24 hours

Refrigerated

 2-8°C

≤ 24 hours

Rejection Criteria

Not Defined

Result Reporting and Reference Values

  • 300 - 900 mOsm/kg
  • Urine after 12 hr fluid restriction:  Should be greater than 850 mOsm/kg.

Reflex Testing

None

Limitations

Not Defined