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 pressure of urine, usually greater than the osmolality of serum. The normal values are 500 to 800 mOsm/L after overnight water deprivation. (Term osmolality is often used interchangeably with osmolarity.)

urine osmolality

The osmotic concentration of the urine.
See also: osmolality

osmolality

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 would be indicative of a higher than usual amount of water in relation to the amount of particles dissolved in it. It would be expected, then, that a low serum osmolality would accompany overhydration, or edema, and an increased serum osmolality would be present in a state of fluid volume deficit.
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 osmotic 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.
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.

urine

the fluid containing water and waste products which are secreted by the kidneys, stored in the bladder and discharged by way of the urethra. See also urinary.

urine albumin
urine alkalinization
increasing the pH of urine by the administration of alkalinizing agents such as sodium bicarbonate; used to increase the solubility of cystine in the management of cystine urolithiasis in dogs.
blood in urine
urine burn
see urine scald (below).
urine calculi
urine casts
see urinary casts.
urine cells
see urine sediment (below).
urine chromogens
urine concentration test
see water deprivation test.
urine creatine
urine crystals
urine drinking
in farm animals is observed in nutritional deficiency of sodium chloride.
urine flow
the rate of flow may be reduced—oliguria, absent—anuria, or increased—polyuria.
urine flowmetry
measure of urine flow rates.
urine glucose
urine hemoglobin
urine immunoglobulins
may be found in small amounts in normal animals. Increased amounts occur in renal disease due to disruption of glomeruli and defects in tubular reabsorption.
urine indican
urine ketones
urine marking
metastable urine
calcium oxalate crystals are maintained and can enlarge in urine oversaturated with these minerals.
urine methemoglobin
urine myoglobin
urine osmolality
a measure of the number of dissolved particles per unit of water in urine. See also osmolality.
oversaturated urine
calcium and oxalate crystals will spontaneously precipitate, grow and aggregate.
urine peritonitis
caused by the presence of urine in the peritoneal cavity as in rupture of the bladder.
urine pH
the normal range varies with the animal species. Herbivores have a higher pH than carnivores because of differences in the diet. Alterations occur with changes in acid-base balance and infection in the urinary tract.
urine protein
pus in urine
see pyuria.
red urine
residual urine
urine remaining in the bladder after urination; seen in bladder outlet obstruction (as by prostatic hypertrophy) and disorders affecting nerves controlling bladder function.
urine sample collection
midstream collection is standard; for culture the sample should be collected by catheter or suprapubic, percutaneous needle insertion into the bladder.
urine scald
scalding of the perineal area, and sometimes the hindlegs, by urine. It may be the result of urinary incontinence or the animal's inability to assume normal posture when urinating, i.e. paresis or paralysis of the hindlimbs. In rabbits it is caused by poor cage accommodation and frequent wetting of the area with urine. Secondary infection of the dermatitis is common.
urine sediment
a centrifuged deposit suitable for microscopic examination for the presence of cells, casts, bacteria, crystals, etc.
urine specific gravity
see specific gravity.
subcutaneous urine aggregation
urine leaking from a damaged urethra collects in a subcutaneous site.
References in periodicals archive ?
Based on these data, we concluded that the feline scale provides a closer approximation to Hispaniolan Amazon parrot urine osmolality when compared with the human-canine scale, but it still causes an overestimation of osmolality, as seen in Figure 2.
12] A recent study revealed that COX-2 expression, but not COX-1 in the rat IM, was up-regulated by hyperosmolality and closely correlated with urine osmolality.
Urine osmolality of less than 200 mOsmol/kg in the presence of polyuria is pathognomonic of CDI.
If the patient is losing water in the urine, why is the urine osmolality high?
However, there was no change in urine osmolality following the DDAVP and this confirmed the diagnosis of nephrogenic diabetes insipidus.
Serum osmolality, electrolytes, and uric acid, along with urine osmolality and electrolytes, are useful in distinguishing CSW from SIADH.
Any change in fluid homeostasis affects blood pressure and serum and urine osmolality.
Urine osmolality is a good surrogate marker for the renal actions of vasopressin, and a urine osmolality exceeding serum osmolality nearly always indicates high circulating vasopressin.
Many indices of hydration levels are known, such as body weight, plasma osmolality, urine osmolality and urine specific gravity (Kavouras, 2002).
If the urine osmolality increases and then decreases, additional vasopressin is needed.
Serum and urine osmolality was assayed using a vapor pressure osmometer.
Urine osmolality ranges from 15 to 585 mosmol/kg in the neonatal period and does not approach adult values until 2 years of age (9).