urine osmolality


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osmolality

 [oz″mo-lal´ĭ-te]
the concentration of a solution in terms of osmoles of solutes per kilogram of solvent.
serum osmolality a measure of the number of dissolved particles per unit of water in serum. In a solution, the fewer the particles of solute in proportion to the number of units of water (solvent), the less concentrated the solution. A low serum osmolality means a higher than usual amount of water in relation to the amount of particles dissolved in it, and accompanies overhydration, or edema. An increased serum osmolality indicates deficient fluid volume. Measurement of the serum osmolality gives information about the hydration status within the cells because of the osmotic equilibrium that is constantly being maintained on either side of the cell membrane (homeostasis). Water moves freely back and forth across the membrane in response to the osmolar pressure being exerted by the molecules of solute in the intracellular and extracellular fluids. Serum osmolality reflects the status of hydration of the intracellular as well as the extracellular compartments and thus describes total body hydration. The normal value for serum osmolality is 270–300 mOsm/kg water.
urine osmolality a measure of the number of dissolved particles per unit of water in the urine. A more accurate measure of urine concentration than specific gravity, urine osmolality is useful in diagnosing renal disorders of urinary concentration and dilution and in assessing status of hydration. The normal value is 500 to 800 mOsm/L.

urine osmolality

The osmotic concentration of the urine.
See also: osmolality
References in periodicals archive ?
Time 0 hr 2 hr 4hr 12 hr Serum osmolality (mOsm/kg) 250 243 248 253 Urine osmolality (mOsm/kg) 630 396 184 485 Urine Na (mmol/L) 83 58 32 77 Serum Na (mmol/L) 125 124 124 126 Table 3: Classification of hyponatremia.
Concomitant plasma osmolality should be measured for the interpretation of urine osmolality to ensure that after water deprivation plasma osmolality is sufficient to stimulate vasopressin release.
The relationship between urine osmolality and specific gravity.
We used a freezing point depression osmometer (Model 3320, Advanced Instruments Inc., Norwood, MA) to determine urine osmolality. The freezing point depression technique measures the total solute concentration by comparing the specimen to the freezing point of water (1.86[degrees]C) (5, 15).
The serum creatinine level was 87 [micro]mol/L and the urine osmolality after 12 hours of water deprivation was 488 mOsm/kg?H [sub]2 O.
The results demonstrate that PAN-induced nephrotic syndrome is associated with decreased urine concentration, manifested by an increased urine output, decreased urine osmolality, and a marked upregulation of collecting duct water channels (AQP2) [31].
Refractometers are used frequently in veterinary medicine to allow practitioners to have a rapid and inexpensive assessment of urine osmolality. A refractometer uses a sample's refractive index, the degree to which it bends light, which depends on the concentration and type of solutes in the sample, to provide insight into other properties.
While the workup shows hypernatremia, serum hypo-osmolality, urine osmolality >100 mosm/kg (serum osmolality is lower than urine osmolality), decrease urine output, normal urine sodium concentration and potassium and acid base concentration which are going with SIADH criteria.
The findings were inconsistent with regard to low urine osmolality (8).
Nurses must make sure the patient has free access to oral fluid and carefully monitor urine output, urine-specific gravity, urine osmolality, serum sodium level, serum osmolality, and mental status.
The urine osmolality of the obstructed kidney was markedly reduced at 9 weeks compared with the sham-operated controls (398 ± 37 vs.
They also measured urine osmolality - the concentration of the children's urine, which is a key indicator of hydration.