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

To describe the prevalence, underlying disease mechanisms, and outcome for dogs and cats with a low blood sodium-to-potassium concentration (Na:K) ratio.

Retrospective study from January 1, 2019, to December 31, 2020.

University teaching hospital.

Seven hundred eleven dogs and 159 cats.

Low blood Na:K ratio was identified in 711 dogs (prevalence of 6.7%) and in 159 cats (prevalence of 6.6%). The most common identified primary diseases were kidney disease (30% of dogs, 52% of cats) and hepatobiliary disease in dogs (19%) and lower urinary tract disease in cats (30%). Hypoadrenocorticism was uncommon, occurring in 2% of dogs. Urinary tract disease and low effective circulating volume were the most commonly identified underlying pathophysiologic mechanisms. The median (25th-75th percentile) blood Na:K ratio for all dogs was 25.6 (range: 24.3-26.4) and for cats was 23.4 (range: 19.1-25.8). Severe hyperkalemia (>7.0 mmol/L) was evident in 21 of 711 (3%) dogs and 50 of 159 (31%) cats. Severe hyponatremia (<130 mmol/L) was evident in 28 of 711 (4%) dogs and six of 159 (4%) cats.

The prevalence of a low blood Na:K ratio in dogs was higher than previously reported, and this finding cannot be assumed to be due to hypoadrenocorticism. Understanding the pathophysiologic mechanisms responsible for these electrolyte abnormalities in individual patients may help guide therapeutic decision-making.