Severe Gastrointestinal Disease in a Dog Presenting With Hypoadrenocorticism-Like Electrolyte Derangements Due to Protothecosis.

OBJECTIVE: To describe systemic protothecosis as a novel differential for hypoadrenocorticism-like clinicopathologic findings. CASE SUMMARY: A 3-year-old neutered female Labrador Retriever was evaluated for an episode of acute lethargy, hyporexia, and ataxia. The dog had a prior history of chronic gastrointestinal signs with no underlying cause determined. On presentation, the dog had several clinicopathologic changes similar to those seen in cases of hypoadrenocorticism, most notably a severe hyperkalemia and hyponatremia, with a sodium-to-potassium ratio of <14:1. A diagnosis of Prototheca bovis infection was made based on the histopathology of endoscopic biopsies and confirmatory polymerase chain reaction. The dog initially had a positive response to treatment with oral antifungals but was later euthanized due to the progression of ophthalmologic and neurologic signs. NEW OR UNIQUE INFORMATION PROVIDED: Based on a literature search and to the authors' knowledge, this is the first time canine protothecosis has been associated with severe hyperkalemia and one of only a few reports of gastrointestinal disease resulting in severe hyperkalemia.