What’s your diagnosis?
The gelatinous look is more consistent with an acute rather than a chronic lesion. Thus, acute orchitis and epididymitis is correct.
Bacterial or fungal infection
In this case, the dog had a severe pyogranulomatous orchitis and epididymitis with intralesional fungal yeasts. The morphologic features of the yeast, including size, presence of broad-based budding, and the double contoured wall, are most consistent with a diagnosis of Blastomyces dermatitidis. Other differentials for dimorphic fungi include Coccidioides immitis, Histoplasma capsulatum, and Cryptococcus neoformans. Testicular blastomycosis is typically the result of underlying disseminated visceral disease; however, direct inoculation does occur.
Bacterial infections, particularly from Escherichia coli, may have a similar appearance. Brucella canis, a potentially zoonotic disease, may cause more chronic lesions with testicular atrophy and granulomatous and/or lymphoplasmacytic epididymal inflammation. B. canis infection may also have no lesions and present only as reproductive failure.