Resting cortisol concentrations in dogs presenting to a university teaching hospital with collapse.

Background: The relationship between collapse and a diagnosis of hypoadrenocorticism is not well understood in dogs.

Hypothesis: To assess the prevalence of episodes of collapse in dogs screened for hypoadrenocorticism, and to assess the prevalence of confirmed hypoadrenocorticism in dogs presenting with reported collapse.

Animals: Seventy-three client-owned dogs with resting cortisol concentrations were measured and presented to a University teaching hospital for collapse.

Methods: Retrospective review of medical records of dogs at a single center.

Results: The prevalence of episodes of collapse in dogs that had a resting cortisol measurement was 73/856 (8.5%; 95% confidence interval [95% CI], 6.7%-10.6%). Resting cortisol concentration was <2 μg/dL (<55 nmol/L) in 19 dogs. Cortisol concentration after ACTH stimulation was <2 μg/dL (<55 nmol/L) in 1 of the 73 dogs in this cohort, consistent with a diagnosis of hypoadrenocorticism, giving a prevalence estimate of hypoadrenocorticism of 1.3% (95% CI, 0.15%-6.2%). In 8 dogs with an initial resting cortisol concentration <2 μg/dL (<55 nmol/L), hypoadrenocorticism was excluded based on a repeat resting cortisol concentration >2 μg/dL (>55 nmol/L). The most common diagnosis was vasovagal syncope (10/73), followed by sick sinus syndrome and third-degree atrioventricular block (2/73). The final diagnosis was unknown in 24/73 dogs.

Conclusions and clinical importance: Hypoadrenocorticism was the final diagnosis in 1 of 73 dogs presented to a teaching hospital either in a collapsed state or with a previous history of episodes of collapse. No dog presenting as cardiovascularly stable for intermittent collapse was found to have hypoadrenocorticism.