Felis ISSN 2398-2950

Urinalysis: specific gravity

Synonym(s): SG

Contributor(s): Kathleen P Freeman, Karen L Gerber, Andy Torrance

Overview

  • Measure kidneys' ability to concentrate and dilute urine.

Sampling

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Tests

Methodologies

Refractometer (most common)

  • Single drop placed on glass surface; reading relative to specific gravity of distilled water (= 1).

Urinometer

  • Need large volume (15-45 ml) but can dilute and recalculate specific gravity reading.
  • Three-quarter fill cylinder then insert urinometer and read scale at interface of air with urine; the scale reading represents the 2nd and 3rd decimal placing, eg reading of 25 = 1.025.

Dipstick

  • Results do not correlate well with refractometer.

Availability

  • Standard practice laboratory technique.

Technique (intrinsic) limitations

  • Cannot interpret results in isolation from other urinalysis results and lab tests.
  • Single random result outside normal reference range cannot establish diagnosis.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Watson A D (1998) Urine specific gravity in practice. Aust Vet J 76(6), 392-398.
  • Buffington C A et al(1997) Clinical evaluation of cats with non-obstructive urinary tract diseases. JAVMA 210(1), 46-50.
  • Brobst D (1989) Urinalysis and associated laboratory procedures. Vet Clin North Am Small Anim Pract 19(5), 929-949.
  • McCaw D L, Fleming E J & Mikiciuk M G (1989) Interpreting the results of urinalysis - a key to diagnosing renal disorders. Vet Med 84(3), 281-286.
  • Barsanti J A et al (1980) Laboratory findings in urinary tract infections. Vet Clin North Am Small Anim Pract 9(4), 729-748.

Other sources of information

  • Kaneko J J (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Harvey J W & Bruss M L (eds). Academic Press, Boston.
  • Duncan J R, Prasse K W & Mahaffy E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Iowa University Press, Ames, Iowa.


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