Dataset for: Urine Sodium Concentrations are Predictive of Hypoadrenocorticism in Hyponatremic Dogs: A Retrospective Pilot Study

Objectives: The purpose of this study was to determine if a urine sodium concentration could be used to rule out hypoadrenocorticism as the cause of hyponatremia in hyponatremic dogs. In the hyponatremic state, sodium should be conserved at the level of the renal tubule; with expected urine sodium concentrations are < 30 mmol/L. However, in the case of aldosterone deficiency due to hypoadrenocorticism, sodium is inappropriately lost into the urine, resulting in urine sodium concentrations > 30 mmol/L. Methods: Medical records of hyponatremic dogs (serum sodium < 135 mmol/L) that had urine sodium concentrations measured were reviewed. Twenty hyponatremic dogs were included; 11 with a diagnosisdiagnosed with of classical hypoadrenocorticism and 9 with non-adrenal causes of hyponatremia. A Wilcoxon sum rank test was used to compare results between groups. Results: No dog with hypoadrenocorticism had a urine sodium concentration < 30mmol/L. Urine sodium concentration in dogs with hypoadrenocorticism was significantly higher (median 103 mmol/L, range: 41-225), than in dogs with non-adrenal illness (median: 10 mmol/L, range: 2-86) (p < 0.0005). Serum sodium concentrations were not significantly different between dogs with hypoadrenocorticism and dogs with non-adrenal illness. Clinical Significance: These results suggest that urine sodium concentrations can be used to prioritize a differential diagnosis of hypoadrenocorticism in hyponatremic dogs. A urine sodium concentration < 30 mmol/L in a hyponatremic dog makes classical hypoadrenocorticism an unlikely cause of the hyponatremia. Due to the small sample size in this study, results should be interpreted with caution. A larger follow-up study would be valuable.