Zygomatic Sialadenitis as a Rare Cause of Exophthalmos in a Dog.

Zygomatic sialadenitis should be considered in dogs with retrobulbar disease refractory to medical management.

This case report describes an uncommon presentation of zygomatic sialadenitis causing retrobulbar disease and exophthalmos in a 10-year-old spayed female Cavalier King Charles Spaniel following extensive dental extractions (15 teeth). The dog presented with acute right-sided exophthalmos, pain on mouth opening, lagophthalmos, and a superficial corneal ulcer. CT imaging revealed a tubular fluid-filled retrobulbar structure and right-sided zygomatic sialadenitis. Initial management included IV fluids, broad-spectrum systemic antibiotics, analgesics, topical antibiotics, and ocular antihypertensive medications. Cytology demonstrated septic suppurative inflammation, and microbial culture identified Bacteroides pyogenes, an anaerobic organism with low antimicrobial resistance potential. Histopathology confirmed subacute zygomatic sialadenitis with associated cellulitis. Despite medical management, the patient experienced progressive clinical deterioration and vision loss, necessitating transpalpebral exenteration combined with zygomatic sialoadenectomy. Postoperative recovery was uneventful, with complete resolution of periocular swelling and pain. The authors propose that persistent salivary secretions from the inflamed zygomatic gland perpetuated ongoing inflammation, contributing to treatment failure with medical therapy alone. This case highlights zygomatic sialadenitis as an important differential for retrobulbar disease, especially in cases refractory to medical management, and underscores the value of advanced cross-sectional imaging in achieving accurate diagnosis and guiding definitive surgical treatment.

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