October 2011 Issue
Table of Contents
Properly Diagnosing Addisons Disease and Your Dogs Treatment Options
Addisons disease can mimic many other conditions; heres how to positively identify it.
Something’s wrong with your dog but you’re not sure what. She seems listless, her eyes have lost their spark, and she just seems “off.” You might notice intermittent muscle weakness, tremors, and an inability to jump into the car or onto a sofa. Or your dog frequently ignores her dinner, vomits, or has diarrhea. These vague symptoms, which may improve and then return, could stem from a dozen canine illnesses – or they might point to Addison’s.
Addison’s disease, named for the 19th century physician who defined this adrenal gland dysfunction, is also known as hypoadrenocorticism or adrenal insufficiency. While fatal if left untreated, with appropriate treatment Addison’s can be managed so that affected patients lead normal, active lives. First diagnosed in dogs in the 1950s, it is considered an uncommon canine disorder. However, veterinarians who routinely test for Addison’s often find it, suggesting that the illness is not really rare but rather under-diagnosed and under-reported. You don’t find Addison’s unless you look for it. Some veterinarians speculate that Addison’s disease occurs in dogs at a rate as much as 100 times the rate in humans.
Aiyana, a three-year-old Italian Greyhound who lives with Lydia Kunzler in Northern Utah, developed symptoms when she was nine months old, but none of the several veterinarians Kunzler consulted could find the cause.
“Last fall I noticed Aiyana was starting to lose weight,” she says, “and because I had a lot of things going on I attributed her loss of appetite to stress and tried to feed her more. But a week after one of my other dogs passed away she became very sick. She was vomiting, very lethargic, and her digestive system just shut down, sometimes going days without a bowel movement. A few weeks went by, and we had to keep her on intravenous fluids or she’d get really sick again. Finally I decided to change vets. I knew all this vomiting, alternating diarrhea and constipation, and other symptoms weren’t normal.”
Aiyana’s new veterinarian immediately recognized the signs of Addison’s and did an ultrasound test, saw how small the dog’s adrenal glands were, and ordered an adrenal hormone blood test to confirm the diagnosis.
Dogs of any breed, either sex, and any age can develop Addison’s. About 70 percent of dogs with Addison’s are female, although in some breeds, including Standard Poodles and Bearded Collies, males and females are equally affected. The median age of dogs diagnosed with Addison’s disease is 4 to 6 years, but it has been reported in puppies and in dogs as old as 12.
Certain breeds may be predisposed to Addison’s, including Portuguese Water Dogs, Bearded Collies, Standard Poodles, Great Danes, Soft Coated Wheaten Terriers, Airedale Terriers, Basset Hounds, Springer Spaniels, West Highland White Terriers, Leonbergers, Labrador Retrievers, Rottweilers, Saint Bernards, Nova Scotia Duck Tolling Retrievers, Airedale Terriers, German Shepherd Dogs, German Shorthaired Pointers, other Poodles, and mixes of these breeds.
Commonly reported symptoms, which can vary dramatically from dog to dog, include loss of appetite, weight loss, depression, listlessness, vomiting, diarrhea, hind-end pain, muscle weakness, tremors, shivering, increased thirst, excessive urination, a painful or sensitive abdomen, muscle or joint pain, and changes in coat, which may become thicker, thinner, longer, or even curly. About 15 to 20 percent of Addisonian dogs will have dark, tarry stools (melena, caused by gastrointestinal hemorrhage) or blood in their vomit. Symptoms often wax and wane, with the dog getting worse, then better, for months or even years.
Veterinarians examining Addison’s patients may notice mental depression, a thin or emaciated body, muscle weakness, dehydration, patches of darkened skin, a slow and weak pulse, low body temperature, low blood pressure, and pale mucous membranes. Blood tests may show any of the following: elevated potassium, low sodium, elevated BUN and creatinine, elevated liver enzymes, low glucose, high calcium, low protein (albumin and globulin), anemia, low cholesterol, and metabolic acidosis. Urine may be dilute (low specific gravity). A sodium/potassium ratio of less than 27 is strongly indicative of Addison’s, but a normal ratio does not rule it out as many veterinarians assume. A sick dog with normal or elevated lymphocytes and eosinophils (lack of a stress leukogram) can point toward Addison’s.
Addison’s disease, called “The Great Pretender,” is often misdiagnosed because it resembles so many other illnesses. Patients with Addison’s are often erroneously diagnosed as having gastrointestinal diseases such as inflammatory bowel disease (IBD), infections, parasites, cancer of the gastrointestinal tract, or poisoning. Acute renal failure, liver disease, urinary blockage, pancreatitis, insulinoma, hyperparathyroidism, and protein-losing enteropathy are other common misdiagnoses.
The most dramatic Addison’s symptom is the endocrine emergency called Addisonian crisis. This occurs when the dog goes into shock due to circulatory collapse, and it can happen so quickly that a healthy looking dog is suddenly, within a few hours, close to death.
In an Addisonian crisis, the lack of adrenal hormones depletes sodium levels (hyponatremia) and body fluids (hypovolemia), resulting in potassium retention (hyperkalemia), bradycardia (slow heart rate), hypotension (low blood pressure), associated cardiac arrhythmias (abnormal heart beats), and collapse. In other diseases, hypovolemia and shock cause tachycardia (rapid pulse); in Addison’s, the pulse slows. Low blood sugar levels (hypoglycemia) can cause seizures. Vomiting and diarrhea are common.
For many dog owners, the crisis is their first sign that something is wrong. About 30 to 35 percent of dogs with Addison’s are initially diagnosed during a crisis. Patients treated in time with intravenous fluid therapy and glucocorticoid steroids show such rapid improvement that it seems a miracle cure, though some have to be monitored and treated for several days before their condition stabilizes. And the cure is temporary, for without appropriate maintenance care, another crisis will follow.
As many as 90 percent of dogs in adrenal crisis will have elevated creatinine and BUN, which can lead to a misdiagnosis of acute renal failure. Dehydration and low blood pressure cause blood filtration to drop, resulting in “prerenal azotemia,” where waste products build up even though the kidney itself is functioning. Gastrointestinal bleeding can also cause increased BUN. The response to treatment is more dramatic for dogs with Addison’s disease than for those with kidney disease.
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