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J Am Vet Med Assoc. 2003 Jan 15;222(2):176-9.

Effects of storage time and temperature on pH, specific gravity, and crystal formation in urine samples from dogs and cats.

Author information

1
Minnesota Urolith Center, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108, USA.

Abstract

OBJECTIVE:

To determine effects of storage temperature and time on pH and specific gravity of and number and size of crystals in urine samples from dogs and cats.

DESIGN:

Randomized complete block design.

ANIMALS:

31 dogs and 8 cats.

PROCEDURE:

Aliquots of each urine sample were analyzed within 60 minutes of collection or after storage at room or refrigeration temperatures (20 vs 6 degrees C [68 vs 43 degrees F]) for 6 or 24 hours.

RESULTS:

Crystals formed in samples from 11 of 39 (28%) animals. Calcium oxalate (CaOx) crystals formed in vitro in samples from 1 cat and 8 dogs. Magnesium ammonium phosphate (MAP) crystals formed in vitro in samples from 2 dogs. Compared with aliquots stored at room temperature, refrigeration increased the number and size of crystals that formed in vitro; however, the increase in number and size of MAP crystals in stored urine samples was not significant. Increased storage time and decreased storage temperature were associated with a significant increase in number of CaOx crystals formed. Greater numbers of crystals formed in urine aliquots stored for 24 hours than in aliquots stored for 6 hours. Storage time and temperature did not have a significant effect on pH or specific gravity.

CONCLUSIONS AND CLINICAL RELEVANCE:

Urine samples should be analyzed within 60 minutes of collection to minimize temperature- and time-dependent effects on in vitro crystal formation. Presence of crystals observed in stored samples should be validated by reevaluation of fresh urine.

PMID:
12555980
[Indexed for MEDLINE]

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