Prevalence, Associated Disease Mechanisms, and Outcome of Dogs and Cats With Low Blood Sodium-to-Potassium Ratio.

Low Na:K ratios commonly indicate kidney or urinary disease, not hypoadrenocorticism.

This retrospective study examined 711 dogs and 159 cats presenting to a university teaching hospital over two years to characterize the prevalence, underlying causes, and outcomes of low blood sodium-to-potassium (Na:K) ratios. Low Na:K ratios occurred in 6.7% of dogs and 6.6% of cats, with median ratios of 25.6 and 23.4, respectively. Kidney disease was the most common primary diagnosis in both species (30% dogs, 52% cats), followed by hepatobiliary disease in dogs (19%) and lower urinary tract disease in cats (30%). Notably, hypoadrenocorticism accounted for only 2% of cases in dogs, contradicting the common clinical assumption that low Na:K ratios indicate adrenal insufficiency. The primary pathophysiologic mechanisms identified were urinary tract disease and decreased effective circulating volume. Severe hyperkalemia (>7.0 mmol/L) was more prevalent in cats (31%) than dogs (3%), while severe hyponatremia (<130 mmol/L) occurred equally in both species (4%). These findings emphasize the importance of systematic investigation into underlying disease mechanisms rather than reflexively assuming hypoadrenocorticism.

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