Veterinary Medicine - December 2008 - (Page 650)

2008 Practical advice from the presentations PEER-REVIEWED Central Managing atypical and critical cases of primary hypoadrenocorticism in dogs Two things you may not know about canine Addison’s disease: A history of weight loss or hypoglycemia may precede the typical electrolyte abnormalities, and DOCP can be administered immediately in dogs that may be having an addisonian crisis. David S. Bruyette, DVM, DACVIM I n most cases, canine Addison’s disease, or primary hypoadrenocorticism, is likely caused by immunemediated destruction of adrenal tissue in response to an unknown trigger, resulting in primary adrenocortical failure with glucocorticoid (cortisol) and mineralocorticoid (aldosterone) insuf ciency. Administering mitotane or, rarely, trilostane to treat canine hyperadrenocorticism can also result in primary adrenocortical failure. Secondary hypoadrenocorticism, which is caused by a lack of ACTH secretion from the pituitary gland, is usually iatrogenic and results from abruptly discontinuing long-term glucocorticoid therapy. dogs.1,2 The clinical signs are related to glucocorticoid and mineralocorticoid insuf ciency and include a waxing and waning illness, with lethargy, depression, anorexia, vomiting, diarrhea, melena, weight loss, polyuria and polydipsia, weakness, and abdominal pain. Routine blood tests and urinalysis may reveal anemia, lymphocytosis, eosinophilia, hyperkalemia, hyponatremia, hypoglycemia, hypercalcemia, and prerenal azotemia. IDENTIFYING, TREATING, AND MONITORING ATYPICAL ADDISON’S DISEASE About 5% to 10% of dogs with primary hypoadrenocorticism have a glucocorticoid de ciency only.3 These dogs tend to have a mild clinical presentation, with intermittent signs of a gastrointestinal disorder, such as anorexia, vomiting, and weight loss. And because cortisol counteracts hypoglycemia, dogs may also present with hypoglycemia, particularly in already small or thin animals. You may also identify a history of weight loss, which may precede the electrolyte abnormalities that occur as the disease progresses and mineralocorticoid de ciency develops. Perform ACTH stimulation tests to rule out hypoadrenocorticism in all dogs that exhibit vague waxing and waning clinical signs, general malaise, and weight loss, even in dogs with normal serum electrolyte concentrations. In general, most animals with Addison’s disease have pre- and postACTH cortisol concentrations < 1 µg/dl. In some animals with severe nonadrenal illness and in animals with early adrenal dysfunction, you can see pre- and post- SIGNALMENT AND TYPICAL FINDINGS IN DOGS WITH ADDISON’S DISEASE Primary hypoadrenocorticism can occur in dogs of any age, sex, or breed but occurs most often in young to middle-aged female dogs. Breeds with a higher risk of developing the disease include poodles (standard and toy), rottweilers, West Highland white terriers, Wheaton terriers, Great Danes, and Portuguese water ACTH cortisol concentrations within the normal basal resting range (1 to 5 µg/dl). In these cases, it may be necessary to repeat the ACTH stimulation test in four to eight weeks to document progressive adrenal dysfunction or recovery of the pituitary-adrenal axis after resolution of the nonadrenal illness. If the ACTH stimulation test results indicate hypoadrenocorticism, provide glucocorticoid supplementation (0.2 to 0.4 mg/kg/day orally), and monitor these dogs every three or four months for 12 months. Perform serum chemistry pro les that include electrolyte measurements to monitor for hyperkalemia and hyponatremia, which may indicate mineralocorticoid de ciency and disease progression. The sodium-potassium ratio can be used to evaluate possible mineralocorticoid insuf ciency, but the sensitivity and speci city of such ratios are affected by whether a ratio of 27 or 23 is used to diagnose adrenal insuf ciency. If clinical signs of mineralocorticoid insuf ciency and alterations in the sodium or potassium concentrations, or both, develop at any time in an animal with atypical Addison’s disease, consider evaluating aldosterone concentrations pre- and postACTH stimulation and instituting mineralocorticoid replacement therapy. David S. Bruyette, DVM, DACVIM VCA West Los Angeles Animal Hospital 1818 S. Sepulveda Blvd. West Los Angeles, CA 90025 THERAPY DURING AN ADDISONIAN CRISIS On the opposite end of the clinical presentation spectrum, if a dog is presented that you suspect is having an addisonian crisis, obtain blood and urine samples to perform a pretreatment complete blood 650 December 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - December 2008

Veterinary Medicine - December 2008 Contents Letters Thanking Our Valued Reviewers Practical Matters Idea Exchange Why Do Dogs and Cats Eat Grass? Managing Atypical and Critical Cases of Primary Hypoadrenocorticism in Dogs Behaviors Suggestive of Postoperative Pain in Cats What to Consider When Considering Digital Radiography Avoid Common Bandaging Mistakes in Dogs and Cats IMHA: Diagnosing and Treating a Complex Disease CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - December 2008

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