Canine hypoadrenocorticism. Diagnostic dilemmas associated with the "great pretender"

Canine hypoadrenocorticism (HAC) is often a difficult disease to diagnose in the early course of presentation because of the multitude of associated vague clinical signs. Frequently, the disease is considered only after the patient presents in an acute crisis after an undetected or ignored ongoing, slowly progressive deterioration over the previous several weeks. Although not a common clinical disorder, HAC is still present in the canine population to a degree that merits a full diagnostic workup in all cases of suspicion. The purpose of this chapter is to alert the clinician to the underlying pathophysiology of adrenal insufficiency to better understand the clinical and biochemical abnormalities of this syndrome. By recognizing early signs of HAC, the potential for advanced detection is raised. From this detection, the acute crisis situation may be averted. Of equal importance in the diagnosis of HAC is the fact that other disease states may be mimicked by its presentation. This chapter reviews the common differential diagnoses for the presenting clinical signs, along with establishing a differential list for the expected biochemical abnormalities. In particular, special emphasis is placed on the discussion of potassium homeostasis and hyperkalemia. Finally, a brief overview of the treatment of both acute and nonacute adrenal insufficiency is mentioned.