Overview

• Measure kidneys' ability to concentrate and dilute urine.

Sampling

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

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. JAV MA 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. Eds: Harvey J W & Bruss M L. Academic Press, USA.
• Duncan J R, Prasse K W & Mahaffy E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Iowa University Press, USA.