Water deprivation test in the dog: maximal normal values.

Area of Science:

• Veterinary Medicine
• Renal Physiology
• Canine Health

Background:

• Assessing hydration status in dogs is crucial for clinical practice.
• Understanding maximal renal concentrating ability aids in diagnosing kidney disorders.
• Previous research has explored various indicators of dehydration in canines.

Purpose of the Study:

• To determine maximal urine osmolality and urine specific gravity in dogs after water deprivation.
• To evaluate the reliability of body weight, skin pliability, total plasma protein, and packed cell volume as indices of negative water balance.
• To assess the occurrence of abnormal serum urea nitrogen and creatinine levels during dehydration.

Main Methods:

• Water deprivation was administered to 20 healthy dogs until dehydration was induced.
• Maximal urine osmolality and urine specific gravity were measured.
• Body weight, skin pliability, total plasma protein concentration, and packed cell volume were monitored.
• Serum urea nitrogen and creatinine levels were analyzed.

Main Results:

• Mean maximal urine osmolality reached 2,289 mOsm/kg, with a mean maximal urine specific gravity of 1.062.
• The ratio of mean maximal urine osmolality to mean serum osmolality was 7.3.
• Weight loss and increased total plasma protein were consistent indicators of dehydration, while skin pliability and packed cell volume were unreliable.
• Abnormal increases in serum urea nitrogen and creatinine were rare, even after 96 hours of water deprivation.

Conclusions:

• Healthy dogs possess a significant capacity for urine concentration following water deprivation.
• Body weight and total plasma protein concentration are reliable indicators of hydration status in dogs.
• Skin pliability and packed cell volume are less dependable for assessing dehydration in canines.
• Renal function, as indicated by serum urea nitrogen and creatinine, remained largely unaffected even with prolonged water restriction.