Journal of Small Animal Practice • Vol 59 • April 2018 • © 2017 British Small Animal Veterinary Association
Journal of Small Animal Practice (2018) 59, 228–231
Accepted: 6 October 2017; Published online: 20 December 2017
Urine sodium concentrations are
predictive of hypoadrenocorticism in
hyponatraemic dogs: a retrospective
E. M. L * , J. B. H
S. L. V
*Department of Small Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine , Knoxville , TN 37996 , USA
IDEXX Diagnostics , Cary , NC 27519, USA
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine , Raleigh , NC 27607 , USA
Corresponding author email: email@example.com
: To determine if a urine sodium concentration could be used to rule out hypoadrenocorticism
in hyponatraemic dogs.
: Medical records were reviewed for hyponatraemic dogs (serum sodium<135 mmol/L)
that had recorded urine sodium concentrations. Twenty hyponatraemic dogs were included: 11 diagnosed
with classical hypoadrenocorticism and nine with non-adrenal causes of hyponatraemia. A Wilcoxon
rank-sum test was used to compare results between groups.
: No dog with hypoadrenocorticism had a urine sodium concentration less than 30 mmol/L. Urine
sodium concentration in dogs with hypoadrenocorticism was significantly higher (median 103 mmol/L,
range: 41 to 225) than in dogs with non-adrenal illness (median 10 mmol/L, range: 2 to 86) (P<0·0005).
Serum sodium concentrations were not significantly different between dogs with hypoadrenocorticism
and dogs with non-adrenal illness.
: These results suggest that urine sodium concentrations can be used to prioritise a
differential diagnosis of hypoadrenocorticism in hyponatraemic dogs. A urine sodium concentration less
than 30 mmol/L in a hyponatraemic dog makes classical hypoadrenocorticism an unlikely cause of the
hyponatraemia. Nevertheless, because of the small sample size our results should be interpreted with
caution and a larger follow-up study would be valuable.
Classical primary hypoadrenocorticism is a syndrome that is
often challenging to diagnose due to its vague clinical signs
and lack of pathognomonic clinicopathologic data. Many dogs
with hypoadrenocorticism are critically ill and require expen-
sive care and hospitalisation before a definitive diagnosis is
This study was presented in abstract form at the 28th Annual Forum of the American College
of Veterinary Internal Medicine, Anaheim, CA, USA.
made. Serum cortisol is usually measured by reference labo-
ratories, typically with a waiting period after a sample is col-
lected. Therefore, a test available in an emergency setting that
could be used to help to prioritise the differential diagnosis of
hypoadrenocorticism in a critically ill patient would have value
in providing a tentative prognosis before expensive care and
In classical hypoadrenocorticism, aldosterone deficiency
results in renal sodium wasting and potassium retention, result-
ing in hyponatraemia and hyperkalaemia (Willard et al . 1982 ,
Rakich & Lorenz 1984 , Melian & Peterson 1996 , Adler et al .