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


METHODS
Randomized complete block design.


METHODS
31 dogs and 8 cats.


METHODS
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
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.
Albasan
Hasan
H
Minnesota Urolith Center, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108, USA.
Lulich
Jody P
JP
Osborne
Carl A
CA
Lekcharoensuk
Chalermpol
C
Ulrich
Lisa K
LK
Carpenter
Kathleen A
KA
D000818:Animals; D002129:Calcium Oxalate / Q000652:urine; D002415:Cats / Q000652:urine*; D003460:Crystallization; D004285:Dogs / Q000652:urine*; D006863:Hydrogen-Ion Concentration; D013046:Specific Gravity; D013048:Specimen Handling / Q000379:methods / Q000662:veterinary*; D013696:Temperature; D013997:Time Factors; D016482:Urinalysis / Q000662:veterinary*; D014556:Urine / Q000737:chemistry
D002129:Calcium Oxalate