Bilateral parotid duct transposition for keratoconjunctivitis sicca in a Connemara stallion.

The article presents a case study of a 7-year-old stallion suffering from keratoconjunctivitis sicca (KCS), a type of dry eye syndrome, which was treated using bilateral parotid duct transposition. Despite complications arising in one of the horse’s eyes, the surgical procedure contributed significantly to resolving the animal’s symptoms and enhancing its ocular comfort.

Case Presentation and Diagnosis

• The study focuses on a Connemara stallion having a 4-month-old history of KCS, coupled with symptoms like blepharospasm, recurrent corneal ulcerations, and mucopurulent ocular discharge. The horse remained unresponsive to medical treatments.
• In the ophthalmic examination, findings suggested KCS symptoms such as unexciting corneas, and central scarring and pigmentation on the cornea with associated new blood vessel formation.
• Further, the examination via computed tomography scanning and endoscopy of the upper airway and guttural pouches excluded any structural anomalies contributing to KCS of neurogenic origin.
• As a result, the stallion was diagnosed with immune-mediated dacryoadenitis since all other possible causes of KCS were omitted.

Surgical Intervention and Postoperative Outcomes

• The principle treatment method applied was parotid duct transposition (PDT), initially performed on the right eye and subsequently on the left after 4 weeks. This surgery involves redirecting the parotid salivary duct to introduce saliva into the eye as a replacement for tears.
• The right-eye PDT procedure was still in action two years post-surgery, demonstrating considerable enhancement in ocular comfort plus a decline in corneal fibrosis and neovascularization.
• Unfortunately, the left-eye PDT manifested a salivary-cutaneous fistula due to the avascular necrosis of the distal parotid duct. Attempts to therapeutically handle it using grafts did not succeed.
• Tear production in the left eye improved one year post-surgery due to long-term lacrostimulant therapy along with the performance of a permanent PD-cutaneous fistula.

Conclusion and Implications

• The research concludes that bilateral PDT in horses can be an effective strategy in resolving clinical signs related to KCS.
• Nevertheless, complications such as avascular necrosis of the transposed PD can lead to significant suffering and a risk of surgical failure.