Veterinary Medicine - June 2008 - (Page 323)

Serum chemistry pro le abnormalities in dogs with glucocorticoid de ciency include hypoalbuminemia, hypocholesterolemia, hypoglycemia, and mild hyponatremia.6,7 Impaired absorption of nutrients, protein-losing enteropathy, and decreased albumin production may contribute to the hypoalbuminemia.13 Hypocholesterolemia is thought to result from altered lipid absorption.6 Hypoglycemia may be due to blunted gluconeogenesis and increased glucose uptake and use by peripheral tissues.6,12 Mild hyponatremia may develop because of decreased vasopressin secretion and blunted colonic sodium absorption. In healthy dogs, glucocorticoids inhibit vasopressin release; therefore, with glucocorticoid de ciency, inappropriate vasopressin secretion may cause water retention and result in a dilutional hyponatremia.1,7 retention.1 A sodium to potassium ratio < 27:1 is consistent with mineralocorticoid de ciency; however, many diseases can decrease the sodium to potassium ratio in dogs. Thus, a low sodium to potassium ratio is not speci c for hypoadrenocorticism or mineralocorticoid de ciency.14 Mineralocorticoid de ciency alone has a minimal effect on CBC results. Typically, CBC abnormalities in dogs with hypoadrenocorticism are related to either glucocorticoid de ciency or another underlying disease process. Glucocorticoid and mineralocorticoid deﬁciency Dogs with concurrent glucocorticoid and mineralocorticoid de ciency may have a combination of any of the previously mentioned clinical signs (Table 1), physical examination ndings, and clinicopathologic abnormalities (Table 2). Other abnormalities include hypochloremia, azotemia, metabolic acidosis, hypercalcemia, and increased alanine aminotransferase and aspartate aminotransferase activities.4,7,8,15 Hypovolemia and consequential hypoperfusion of the kidneys or liver may result in prerenal azotemia or increased alanine aminotransferase and aspartate aminotransferase activities, respectively.1,8 The hyponatremia may lead to medullary washout and dilute urine, often in the face of dehydration.8 Take care when categorizing azotemia in patients with mineralocorticoid de ciency since many dogs will have isosthenuria or minimally concentrated urine in the face of prerenal azotemia. Lactic acid production and decreased renal hydrogen ion secretion contribute to metabolic acidemia.4 Hypercalcemia may develop because of decreased renal excretion of calcium and hemoconcentration, but the exact pathogenesis is unknown.15 Mineralocorticoid deﬁciency Mineralocorticoids promote sodium and water retention and potassium excretion to regulate intravascular volume and serum potassium concentrations, respectively.1 The clinical signs associated with mineralocorticoid de ciency can range from mild to severe.8 Dogs with mineralocorticoid de ciency may have a history of weakness, lethargy, polyuria and polydipsia, tremors, or collapse.1,8 Most of these clinical signs are the result of hypovolemia, hypotension, or hyperkalemia. Hyponatremia may alter resting membrane potentials of skeletal muscle, leading to tremors.1 Physical examination ndings may include weakness, mild to severe dehydration, hypothermia, weak pulses, and bradycardia.4,8 The classic serum chemistry pro le abnormalities associated with mineralocorticoid de ciency are hyponatremia and hyperkalemia since mineralocorticoids regulate sodium reabsorption and potassium excretion in the renal tubules (Table 2). Hyponatremia can be exacerbated by hypovolemia-induced vasopressin release and free water OTHER CLINICAL FINDINGS Several imaging and electrocardiographic ndings may be recognized in dogs with hypoadrenocorticism. However, not all VETERINARY MEDICINE June 2008 323 http://www.idexx.com/snapfelinetriple http://www.idexx.com/snapfelinetriple

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Veterinary Medicine - June 2008 Contents Leading Off Clinical Exposures Idea Exchange A Challenging Case: Conjunctival Lymphoma in a Cat Updates on Canine Hypoadrenocorticism Product Preview CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller Clinical Edge - June 2008 Table of Contents Managing Diabetes Mellitus in Cats: What Makes it Work? Porcine Insulin Zinc Suspension in the Management of Feline Diabetes Mellitus Monitoring Diabetes Mellitus in Diabetic Cats Feline Diabetes Mellitus: Important Client Communication Points

Veterinary Medicine - June 2008

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