Differential diagnoses, investigation, and management of a periocular swelling close to the nasolacrimal duct in a horse – A case report of Dacryops

Abstract

To describe the differential diagnoses, investigation, and management of a periocular swelling close to the nasolacrimal duct in a horse that was consistent with a nasolacrimal duct dacryops (lacrimal cyst). A 16‐year‐old gelding, Connemara cross presented with a history of a periocular swelling rostroventral medial to the right eye that had been sampled by the referring veterinary surgeon. A cystic lesion was diagnosed following standing computed tomography. Surgical removal of the cystic lesion was performed, and the tissue was submitted for histopathologic and immunohistochemical examination. Surgical removal of the cyst was curative, and there was no recurrence of clinical signs 7 months later. There was a small amount of mineralized material in the center of the cyst. Histopathologic and immunohistochemical examination confirmed a nasolacrimal duct cyst. Dacryops can form in horses as well as other species and appears to have a favorable outcome if surgically removed.

Use of 1% polidocanol and pre‐ and post‐computed tomography for treatment of a suspected nasolacrimal duct cyst in a dog

“…Nasolacrimal duct cysts (dacryocysts) are reported infrequently in veterinary medicine . Proposed causes include congenital malformations (ie ectopic lacrimal tissue), neoplasia, or inflammation (ie local inflammation, dacryocystitis, trauma) which leads to weakening of the duct wall . It is thought that, despite the underlying cause, inflammation leads to lacrimal hypersecretion resulting in the formation of the cystic structure .…”

“…It is thought that, despite the underlying cause, inflammation leads to lacrimal hypersecretion resulting in the formation of the cystic structure . In most cases, the etiology is presumptive and based on history and clinical findings, including the presence and location of a non‐painful swelling …”

“…Assessment of nasolacrimal duct patency is important for confirming nasolacrimal duct occlusion as the cause of epiphora . Diagnostic tests range from rudimentary to advanced and include the Jones test, nasolacrimal cannulation and flushing, ultrasonography and dacryocystography with concurrent radiography or computed tomography .…”

“…If a structural lesion is identified on imaging, fine needle aspiration and biopsy of the identified lesion aid in definitive diagnosis and treatment plan formulation . Diagnostic results typically reveal a fluid‐filled soft tissue mass in the area of the nasolacrimal duct with compromised contrast flow through the affected nasolacrimal duct, viscous, blood‐tinged fluid, bistratified columnar epithelium with or without mineral deposition within the nasolacrimal duct system, or a cystic lumen lined by cuboidal to cylindrical, non‐ciliated epithelium, resembling glandular epithelium . Immunohistochemical staining for smooth muscle actin and analysis of mineral deposits (calcium carbonate in the dog and a mixture of carbonate hydroxyapatite and sodium halite in the horse) if present within the lesion may be used to increase the index of suspicion for a nasolacrimal duct cyst in cases where histopathology is inconclusive …”

“…The tissue of origin often cannot be determined radiographically and should be confirmed histologically . Bony changes associated with a cyst, if present, should not alter the smooth margin of bone and should lack malignant characteristics such as mineralization of the lesion and lysis of the bone …”