Meet The Author
April 2025
Rodolfo Oliveira Leal, DVM, PhD, Dipl.ECVIM-CA (Internal Medicine)
DVM degree (2008) and PhD (2014) at the Faculty of Veterinary Medicine – University of Lisbon. Rotating Intern (2008/2009) and Internal Medicine Resident (2014-2016) at Centre Hospitalier Vétérinaire Fregis (France). Diplomate of the European College of Veterinary Internal Medicine (Companion-Animals) since 2017. Invited Auxiliar Professor and Supervisor of the ECVIM-CA Residency program ongoing at the Faculty of Veterinary Medicine – University of Lisbon. Consultant of internal medicine on VIN (Veterinary Information Network) and vice-president of the European Society of Veterinary Endocrinology (ESVE). Author of various peer-reviewed publications and regular speaker in national and international conferences. Main areas of interest and clinical research focus on Endocrinology, Gastroenterology/Hepatology and Leishmaniosis. About hobbies, Rodolfo enjoys travelling, singing and playing piano. Rodolfo has one mini schnauzer called Baguette. The best weekends are passed with his two kids (Francisco and Luísa) and Baguette.
Santos NS, Domingues TD, Tardo AM, Dinis M, Mateus L, Fracassi F, Leal RO
The Study Background
Adrenal gland has been one of my main areas of clinical research. Hypoadrenocorticism/Addison's disease is a relevant topic in veterinary endocrinology and the fact that its clinical presentation is sometimes so vague, makes us wondering that we should be aware of it and consider its rule out in many of our differential diagnosis lists.
What is the primary knowledge gap your study aims to address?
Resting cortisol has been historically use as a screening test to rule out hypoadrenocorticism. A resting cortisol concentration higher than 2 microg/dl is very sensitive and allows clinicians to rule out hypoadrenocorticism. However, that is not uncommon to check resting cortisol in dogs just to rule out Addison and it comes below this value, even if our "clinical perception" leads us to believe that the disease in that case is unlikely. This value leads us to sistematically recommend an ACTH stimulation test (which is not always practical to perform in the owner's perspective) whose results come, very often, normal. So...the question arises...how urgent is this test? Before doing it, can we predict whether we are dealing with a low-resting cortisol in a dog with normal adrenal function or is this a truly addisonian based on the remaining labwork and clinical signs we have? This was the primary gap that this study aimed to address. All in all, we aimed to characterize this sub-population of dogs with low resting cortisol trying to assess the value of clinical and laboratorial findings as predictors of post-ACTH cortisol results?
The Study Design
To answer the main knowledge gap we had, we did a multicentric retrospective cohort study. Why multicentric? because "knowledge is more powerful when it is shared" and by doing it, we easily increase our case-load making it a more robust study. We started by reviewing medical records of client-owned dogs presented to two referral centres in a timeframe of 4 years and few monts. We selected cases with low resting cortisol that were submitted to an ACTH stimulation test and then divided cases into two groups: those with the final diagnosis of hypoadrenocorticism and those in which ACTH stim was normal. We then compared clinical signs and labwork data inbetween groups and performed a predictive statistical model (using uni and multivariable logistic regression analysis).
What are the main study results?
We had a total of 92 dogs that were included. Of these, 29 had a final diagnosis of hypoadrenocorticism (and were included in the HA group). We found that the more prevalent clinical signs associated with the final diagnosis of hypoadrenocorticism were acute gastrointestinal signs, anorexia and lethargy. From the labwork, we also documented that these subset of cases had higher creatinine, BUN, ALT and potassium and lower albumin, sodium and Na/K ratio. These results were not unexpected since these are the most classic signs and lab-findings associated with the disease. Putting all in the multivariate analysis, we developed a robust model which allowed a good prediction of the disease being lethargy, anorexia, albumin and sodium, the hallmarks of this model.
Were there any unexpected results or challenges during your research?
Indeed the statystical analysis was complicated and the creation of the model was not easy. However, thanks to a great collaboration with a biostatistician, that was much easy. ;). The most challenge we face was that, indeed, we would like to apply the model in eunatremic/eukalemic cases since these are the most relevant cases in which the "clinical perception" may lead addison's to be missed. However, even in a multicentric study, the number of these cases was low and did not allow us to do a subset of cases as we would initially thought!
Takeaways from this study
I think this study reinforce that a low-resting cortisol in a dog showing anorexia, lethargy, hyponatremia and hypoalbuminemia stresses the need to do an ACTH stim with urgency since that's likely to have an addison's disease. On the other hand, if we have a low-resting cortisol in a dog without these findings, the likelyhood of the disease is discussable and then, ACTH stim is not as urgent! ;). Nonetheless, ACTH stimulation test should not be bypassed by this model. Even in these later cases, that is always recommended when resting cortisol is low since it is the only way we have to assess adrenal reserves.
What future directions would you like to explore based on this study?
think that prediction studies are relevant to help us prioritizing differential diagnosis in our daily practice. With the advent of Artificial Inteligence, our priorization of differentials becomes easier and our approach of cases is moving towards a new era. Nonetheless, by doing this kind of studies, we (try to) make a more robust science, keeping the evidence based medicine we need to support our clinical perceptions and the work-up of our cases.
