Diagnosing and Treating the Addisonian Dog
A couple of you have mentioned Addison’s Disease in your replies to various posts in the last few weeks, oftentimes referring to how frustrating you found the process of reaching a definitive diagnosis to be. I thought I’d write about Addison’s in hopes that the process might go a bit more smoothly for other folks who read this blog, in the unfortunate event that their dogs develop Addison’s disease.
First, a bit on why this condition is so often misdiagnosed. The symptoms typically associated with early Addison’s disease are weakness, vomiting, diarrhea, dehydration, increased thirst, and loss of appetite — all of which are pretty nonspecific and seen on a daily basis in a veterinary clinic. If a dog doesn’t look too bad or has a potential explanation for his symptoms ("Yeah, doc, he likes to drink from the nasty pond at the park."), a complete diagnostic workup may not be recommended by the vet or accepted by the client. Without the results of blood work, a urinalysis, fecal testing, etc., a vet would simply treat the dog symptomatically — fluids, rest, anti-diarrheal medications, etc. — and voilà, the dog gets better, at least until another, similar episode occurs in the not too distant future.
It can take several incidences like this, and/or witnessing the weight loss associated with chronic disease, or the extremely slow heart rate and collapse of a full-blown Addisonian crisis, before even a conscientious vet thinks, "Waaaait a minute … I think something else might be going on here."
Addison’s disease develops when an animal’s adrenal glands stop secreting adequate amounts of the glucocorticoids that normally allow individuals to respond to stressful situations and/or the mineralocorticoids that maintain normal fluid and electrolyte levels in the body. This usually occurs because a dog’s immune system has destroyed most of its functional adrenal tissue.
Blood chemistry panels, particularly those that include electrolytes, can help in the diagnosis of Addison’s disease. Sodium levels tend to be lower and potassium levels higher than normal with Addison’s disease, but other health conditions can produce similar results.
Also, when only glucocorticoid production is affected, as is the case in atypical Addison’s disease, or when a dog has been receiving high doses of a glucocorticoid drug (e.g., prednisone) and treatment is too rapidly discontinued, this electrolyte pattern is absent.
Addisonians may be misdiagnosed with gastrointestinal disease, dehydration, kidney disease, pancreatitis, a ruptured bladder, or certain types of poisonings. The only way to definitively diagnose Addison’s disease is through an ACTH stimulation test.
Once diagnosed, treatment for Addison’s disease is extremely rewarding as long as owners can afford the necessary medications. Addison’s disease cannot be cured, but it can be effectively managed with drugs that replace a dog’s missing mineralocorticoids — either with a pill given once or twice a day, or with an injection given roughly once a month. Some dogs also require prednisone, either regularly or during times of stress, but once a treatment protocol is in place and monitored appropriately, most Addisonian dogs can go on to live long and happy lives.
Dr. Jennifer Coates