Intra‐ and Interindividual Variation in Urine Osmolality and Urine Specific Gravity in Healthy Pet Dogs of Various Ages

Abstract

Urine specific gravity (Usg) and urine osmolality (Uosm) are used routinely t o assess renal concentrating ability, but limited data on these variables are available for healthy dogs. Consequently, we studied the intra-and interindividual variations in Usg and Uosm in healthy dogs as well as the influence of age and gender on these variables. Dogs were selected for health and anestrus in female dogs through the use of a detailed questionnaire. Eighty-nine owners collected morning and evening urine samples from their dogs on 2 consecutive days. In 8 dogs in which the Uosm of different samples varied more than 50%. owners collected urine for 24 hours at 2-hour intervals during the day and at 4-hour intervals at night. The possible effect of changes in adrenocortical function with age was assessed by measurements of urinary corticoid/creatinine (C/C) ratios.Among all samples, Uosm ranged from 161 t o 2,830 mOsm/kg and Usg from 1.006 t o > 1.050. In the morning, Uosm (1,541 2 527 mOsm/kg, range 273-2,620 mOsmlkg1 and Usg (1.035 t 0.010, range 1.009-> 1.050) were higher than in the evening (Uosm 1,400 t 586 mOsm/kg, range 161-2,830 mOsm/kg; Usg 1.031 t 0.012, range 1.006-rinary concentrating capacity depends on the ability of U the hypothalamic osmoreceptors to respond to changes in plasma osmolality, the ability of the atrial and carotid bifurcation baroreceptors to respond to changes in blood pressure or blood volume, and the release of the antidiuretic hormone vasopressin (VP) from the neurohypophysis. In addition, medullary hypertonicity must be generated and maintained, and there must be an adequate number of functional nephrons with an appropriate response to VP.'.' In the healthy dog, urine osmolality (Uosm) values as low as 50 mOsm/kg are reached after infusion of large quantities of water, that is, in the absence of VP? In states of dehydration, urine specific gravity (Usg) and Uosm are increased to as much as 1,076 and 2,738 mOsm/kg, re~pectively.~ Urine specific gravity and Uosm are used to assess the ability of the renal tubules to concentrate or dilute glomerular filtrate.' Randomly collected urine samples from normally hydrated dogs are reported to have Usg values ranging from 1.015 to 1.045,'-'' whereas Uosm values usually vary between 500 and 1,200 mO~m/kg.'."-'~ In some dogs, Uosm varies widely during the day, with an intraindividual coefficient of variation approaching the interindividual coefficient of variation. This may be regarded as a biologic variation but also could represent an early undiagnosed clinical abnormality.

Use of Accelerometers to Measure Stress Levels in Shelter Dogs

“…Urinary cortisol-to-creatinine ratios reported here are higher than those reported by Beerda et al (2000) in four groups of dogs living in varying kennel conditions for longer than a year, and they are higher than the mean ratio reported by van Vonderen, Kooistra, and Rijnberk (1997) in companion dogs. The assumption that shelter dogs are more stressed than dogs residing in homes is thus supported by our findings.…”

Intra- and inter-individual variability in the circadian rhythm of body temperature of rats, squirrels, dogs, and horses

“…doi:10. 1016/j.jtherbio.2004.09.003 in physiological functions have revealed that the two variabilities are often different (Gidal et al, 2000;Refinetti, 1989;Refinetti and Horvath, 1989;Symanski et al, 2001;van Vonderen et al, 1997). This difference in variabilities has important implications for clinical practice, whether in veterinary or human medicine.…”

Osmolality and Colloid Osmotic Pressure

“…6 Normal urine osmolality can range between 161 and 2830 mOsm in dogs. 10 The urine osmolality will increase when water intake is withheld as long as kidney function is normal. Each individual laboratory should establish the normal reference range in each species for its osmometer.…”

“…The normal values reported for plasma COP range from 14 to 27 mm Hg in the dog and 21 to 34 mm Hg in the cat. [10][11][12][13] Whole blood COP is reported to be 19.95 ± 2.1 mm Hg in the dog, and 24.7 ± 3.7 mm Hg in the cat. 14 When whole blood is being measured, the sample should be collected with lyophilized heparin.…”