Surgical management of orbital nodular granulomatous episcleritis in a dog

A 27 kg, 6-year-old, male castrated German shorthaired pointer presented to the University of Missouri, Veterinary Teaching Hospital with the complaint of progressive exophthalmia of 2 years duration optical density (OD). Lack of retropulsion OD was noted on physical examination. Anterior segment examination OU and fundic examination OS did not reveal any abnormalities. Examination of the fundus OD revealed focal scleral indentation of the inferior nasal globe. The indentation changed location with globe movement OD. MRI and CT scan revealed a well-circumscribed, approximately 2 cm in diameter mass located caudal and ventral to the affected globe that appeared to communicate with the nictitating membrane with absence of any bony involvement. A modified lateral orbitotomy was recommended and performed to remove the orbital mass and nictitating membrane en-bloc. Histopathology and immunohistochemistry of the mass confirmed a diagnosis of nodular granulomatous episcleritis (NGE). Postoperatively, the dog developed absolute keratoconjunctivitis sicca (KCS). Examples of primary episcleral inflammation in the dog include diffuse episcleritis, NGE, nodular fasciitis, fibrous histiocytoma, proliferative conjunctivitis/keratoconjunctivitis, pseudotumor, and Collie granuloma. The etiology of these episcleral inflammations is presumed to be immune mediated. To our knowledge, this is the first report of NGE affecting the orbital region of a dog. Development of absolute KCS resulting from excision of the nictitating membrane is also supported by this case.