Janie is a ten year old spayed female cross bred terrier. One Monday evening recently, she suddenly seemed under the weather. She was duller than usual, and significantly, she had refused to eat all day. Her enthusiastic appetite was normally one of the most reliable features of her personality.
When I examined her, there were no specifically abnormal findings, but because this was such an unusual turn for her, I decided to carry out a routine blood profile in our in-house laboratory. Within twenty minutes, our automated analyser had assessed her blood count and internal biochemistry. This showed my that everything was more or less normal, but it also pointed out a couple of key, low grade abnormalities: she has one slightly raised liver enzyme, and one marginally elevated kidney parameter. These tests ruled out serious, life threatening issues, but they did hint that there was something going on under the surface.
At first, a virus or a mild upset stomach seemed possible. I gave her a simple treatment using medication to take away any feelings of nausea. If Janie didn't perk up by the following morning, we'd need to carry out further tests to look into what was going on.
The next day, she was no better: she was still lethargic with no interest in eating. And she had vomited overnight, despite the anti-nausea medication.
This time, there were a few other key findings: her temperature was below normal, and her heart rate had dropped from the normal rate of around 100 per minute to just 40 per minute. She was now showing clues of something more significant and specific going on. I took another blood sample, and this time, I decided to do another in-house test: the measurement of so-called electrolytes in her blood.
Electrolytes are dissolved chemicals in the bloodstream that are normally kept within certain parameters: different diseases can cause elevations and depressions of their levels, and these abnormalities can have far reaching effects on the body's metabolism. With some illnesses, the specific changes in certain electrolyte levels can be enough to confirm a diagnosis.
So I measured Janie's calcium and chlorine levels: they were normal. I also measured her sodium level - and it was lower than normal. And her potassium level was higher than it should be. To most readers, this will all be gobbledegook, but any vets reading this will be saying "Ahhhhh". The combination of signs shown by Janie (dullness, inappetance, vomiting) along with these changes in electrolyte levels are sufficient to make an almost definite diagnosis of the cause of her problem: Addison's Disease.
This condition, also known as Hypoadrenocorticism, happens when the adrenal glands (located beside the kidneys) stop producing enough natural steroid hormones to keep the body functioning normally. The cause is usually because the dog's own immune system attacks its own adrenal glands, destroying the hormone-producing areas. Nobody knows exactly why this happens, but it can occur in any animal, of any age. Patients are usually young (four or five years old) but any age of dog can be affected. There's a genetic element to the problem (it's more common in some breeds, like Labradors and Cairn Terriers). Female dogs are affected twice as often as males.
Janie was a classical example, and her diagnosis was fairly straightforward. However the condition is known as "The Great Imitator" because it can resemble other diseases, such as early kidney or liver disease, cancer, and many others. It's one of those situation where vets need to carefully note all of the various aspects of the case, keeping the possibility of Addisons Disease in the back of their mind if it is ever even remotely suspected.
The signs of illness plus blood test results are enough to make a provisional diagnosis (as in Janie's case), but to be absolutely sure, a special test known as an ACTH Stimulation Test needs to be done: this measures the actual levels of cortisone in the blood stream. Only specialised laboratories can do this test, so it takes a few days to get a result.
While we were waiting for Janie's results from this test, we started her on treatment for Addisons Disease. It can be a fatal condition if left untreated, and even in the unlikely event of the diagnosis being wrong, treatment would not cause her any harm in the interim.
She was given immediate intravenous fluids and cortisone, as well as tablets to control her electrolytes, and after just a few hours, she improved dramatically. She became brighter, more energetic, and when offered food, she scoffed it down rapidly. Her heart rate speeded back up to 100, and she was simply a much happier dog.
Two days later, as expected, the blood tests confirmed for sure that she was a classic case of Addisons Disease.
This is a complex condition when you get into the details. There are actually two steroid hormones produced by the adrenal glands: the corticosteroids (cortisone) and the mineralocorticoids (these control the electrolyte levels). Once the diagnosis has been made, treatment is simple.
Janie will have to stay on tablets for the rest of her life, to replace the two types of hormones which her body now lacks.