Enucleation of the eye is a commonly performed surgical procedure indicated for patients unresponsive to treatment experiencing chronic pain from blind eyes.

This procedure is typically performed in patients with end-stage glaucoma who experience pain and vision loss due to elevated intraocular pressure. It is also performed on patients with intraocular tumors that have the potential to metastasize, as well as on those who have experienced corneal perforation due to trauma, rendering the eye irreparable. Additionally, it serves as an option for patients with endophthalmitis or panophthalmitis caused by infection or inflammation, retinal detachment, ocular atrophy resulting from loss of ocular contents, and unmanageable dry eye disease. By addressing the source of pain, this surgery can help improve the patient’s quality of life (6).

Although enucleation is a common procedure, several complications have been reported. Common side effects include surgical site infection, orbital exudate, edema and bleeding. Rarely, orbital emphysema due to high intranasal pressure has been reported in brachycephalic dogs (4). Surgical site infection and residual gland tissues are frequent causes of exudate at the enucleation site.

Surgical site infection has an incidence of approximately 5% of enucleated dogs. Although no apparent risk factors have been identified, it is influenced by conditions such as the surgical environment, surgical approach, and postoperative antibiotic treatment. A pre-existing skin infection may also contribute to surgical site dehiscence (2).

Glandular structures that are not properly removed during surgery include the third eyelid, conjunctival goblet cells, and the meibomian glands of the conjunctiva. This is believed to be a common cause of post-operative exudate, which accumulates in the orbital cavity and forms a cyst or mucocele (11). To address this issue, surgical removal of the residual secretory tissue and all surrounding connective tissue or fat can be performed to resolve this condition.

Salivary glands are structures in the digestive system that produce and secrete saliva, which contains mucopolysaccharides, glycoproteins, and enzymes. Dogs have several salivary glands, including the parotid, mandibular, sublingual, and zygomatic salivary glands.

Among these, the zygomatic salivary gland has the lowest prevalence of salivary gland disease in dogs. Its anatomical location in the ventral part of the orbit, within the medial aspect of the zygomatic arch, provides protection from surrounding structures. Like other salivary glands, it can be affected by various conditions, including gland rupture due to trauma, sialoadenitis, sialocele, sialotithiasis, and malignant tumors. In cases of salivary gland disease, saliva leakage leads to the formation of pseudocysts in the posterior orbit, resulting in clinical symptoms similar to those of posterior segment diseases. These symptoms include exophthalmos, protrusion of the third eyelid, painless orbital swelling, exophthalmos, and conjunctival hyperemia (8).

It is highly uncommon for the salivary glands to be the cause of complications after enucleation. There have been a few reports of salivary gland leakage due to improperly removed salivary ducts in dogs undergoing parotid duct transposition (5). To our knowledge, there are no reports of salivary glands causing surgical site complications after enucleation without such a history. Additionally, salivary gland disease typically leads to mucocele formation and inflammation of the surrounding tissues. Therefore, salivary leakage has not been considered a possible cause of persistent discharge after enucleation in dogs.

This case report describes diagnosing and treating a zygomatic salivary gland rupture after enucleation.

A 9-year-old female Shih-tzu dog was referred to the Chonnam National University Veterinary Medical Teaching Hospital due to non-responsive exudation in the right eye surgical site after enucleation.

The dog underwent bilateral enucleation at a local animal hospital due to chronic glaucoma, and clinical signs were observed three months after surgery. Although surgical removal of the periorbital tissue was performed, the clinical signs did not improve even after ten days of administering antibiotics and anti-inflammatory drugs (such as marbofloxacin, vancomycin, metronidazole, and methylprednisolone sodium succinate). Consequently, the dog was referred to Chonnam National University Veterinary Medical Teaching Hospital for an accurate diagnosis and treatment.

On physical examination, a small amount of viscous discharge was observed (Fig. 1). No other abnormalities associated with periodontal disease were confirmed on oral examination and skull radiography (Fig. 2).

Figure 1. Photographs of the physical examination at the time of referral to the Chonnam National University Veterinary Medical Teaching Hospital. (A) After the periorbital tissue was removed, the various medications were administered. (B) The patient had a persistent small amount of sticky, viscous exudates (yellow arrow) from the orbit.

Figure 2. Skull X-ray images. No severe periodontal diseases affecting the orbit were found. Other direct lesions related to the right orbital purulent exudate were not observed. Only edematous changes (yellow arrow) in soft tissue around the orbits were identified. (A) Dorsal-ventral (DV) view. (B) Right lateral (R) view. (C) Right lateral oblique (RLO) view. (D) Left lateral oblique (LLO) view.

Surgical site infection was the initial differential diagnosis. Antibiotic susceptibility testing confirmed the presence of Staphylococcus pseudintermedius, revealing resistance to all antibiotics except vancomycin, marbofloxacin, ofloxacin, and nitrofurantoin. Marbofloxacin 3 mg/kg intravenously (IV) (Marbocyl^®, Vetoquinol Korea, Goyang, Korea) and carprofen 2.2 mg/kg IV (Rimadyl 50 inj., Zoetis Inc., Parsippany, NJ, USA) was administered twice a day for seven days, but there was no response to the medications. Cytology revealed chronic inflammatory cells in the exudate (Fig. 3A), and it tested positive for Periodic acid-Schiff (PAS) staining (Fig. 3B). No tumor cells were identified, but saliva leakage remained a strong suspicion.

Figure 3. Exudate cytology images (×1,000). (A) H&E stain images. Only chronic inflammatory cells were identified. No findings were observed suggesting a tumor. (B) Periodic acid-Schiff (PAS) stain images. A positive reaction was confirmed.

On computed tomography (CT) images, there was no evidence of osteolysis around the right orbit and the adjacent root of the tooth. Dorsal displacement of the right zygomatic salivary gland and indistinct margins were observed (Fig. 4A). On sialography, the contrast agent did not enter the right zygomatic salivary gland but was retained in the orbit, and a rupture of the gland was confirmed. Based on these results, we planned for a right zygomatic sialoadenectomy (Fig. 4B).

Figure 4. Computed tomographic (CT) images. (A) Dorsal displacement and indistinct margin of the right zygomatic salivary gland were confirmed. (B) On sialography, the contrast agent was retained in the orbit.

Preoperatively, the dog received the following medications: maropitant 1 mg/kg subcutaneously (SC) (Cerenia^®, Zoetis, Seoul, Korea); famotidine 0.5 mg/kg IV (Dong-A Gaster Inj.^TM, DONG-A ST, Seoul, Korea); marbofloxacin 3 mg/kg IV; cefazolin 20 mg/kg IV (CKD Cefazolin Inj., Chong Kun Dang Pharm., Seoul, Korea); and glycopyrrolate 5 μg/kg SC (Reyon Glycopyrrolate Inj., Re Yon Pharm., Seoul, Korea). After that, the dog was premedicated with morphine 0.5 mg/kg (Morphine Hydrochloride inj., Hana Pharm., Seoul, Korea); midazolam 0.2 mg/kg (Midazolam inj., Bukwang Pharm., Seoul, Korea); and ketamine at a continuous rate infusion of 10 μg/kg/min (Ketamine 50 inj., Yuhan, Seoul, Korea). Anesthesia was induced using propofol 3 mg/kg IV (Freefol-MCT inj., Daewon Pharm. Co., Ltd., Seoul, Korea) and maintained with isoflurane (Ifran Liq., Hana Pharm. Co., Ltd., Seoul, Korea) in oxygen after tracheal intubation.

The patient was placed under general anesthesia and positioned in left lateral recumbency. The enucleation site was disinfected with a 0.5% povidone-iodine solution. A skin incision was performed along the ventral margin of the zygomatic arch (Fig. 5A, B). After dissection of the masseter muscle, the ruptured zygomatic salivary gland was identified (Fig. 5C). The gland was carefully extracted (Fig. 5D), and the salivary duct was ligated with a 4-0 absorbable multifilament suture (Polyglycolic acid; SURGISORB, Samyang, Seongnam, Korea) (Fig. 5E). Remove all identified zygomatic salivary glands (Fig. 5F) and the surgical site was cleaned with 0.9% normal saline.

Figure 5. Operation images. (A) The surgical approach was performed along the ventral margin of the zygomatic arch (yellow arrow). (B) After dissecting the masseter muscle. (C) The zygomatic salivary gland was identified without ostectomy. (D) The ruptured zygomatic gland and affected salivary duct were exposed. (E) The salivary duct was ligated with a 4-0 absorbable multifilament suture. (F) Removed zygomatic salivary gland.

After surgery, famotidine 0.5 mg/kg IV, marbofloxacin 3 mg/kg IV, and carprofen 2.2 mg/kg IV (Rimadyl 50 inj., Zoetis Inc., Parsippany, NJ, USA) were administered for three days. After that, marbofloxacin 3 mg/kg (Marbocyl^® Tablet, Vetoquinol Korea, Goyang, Korea) and carprofen 2.2 mg/kg (Rimadyl^®, Zoetis Inc., Parsippany, NJ, USA) were administered orally twice per day for 11 days. The surgical site was cleaned with 0.5% chlorhexidine solution. The dressing was maintained for two weeks after surgery.

Five weeks and three months after surgery, ultrasonography confirmed the absence of exudate and the successful resolution of the complications (Fig. 6).

Figure 6. Post-surgery physical examination and ultrasound images. (A) Five weeks after surgery. There were no complications, including exudate and pain response. (B) Three months after surgery. Physical examination and ultrasound images confirmed no complications.

Common complications following enucleation include bleeding, edema, surgical site infection, and orbital exudates (2,9,11). According to the literature, most complications occur shortly after surgery, there are also reports of complications arising years later (11).

Orbital exudates that occur several months after enucleation are thought to be caused by residual adnexal structures (11). In this case, additional resection of the surrounding structures was performed to eliminate the source of the seromucous exudate post-enucleation. However, the nature and amount of exudate remained unchanged. Initially, surgical site infection was suspected, and despite the use of various antibiotics and anti-inflammatory drugs, the clinical signs did not improve.

Zygomatic salivary gland disease is a rare condition primarily caused by head trauma (1,8). While all dog breeds can experience it, brachycephalic dogs are more susceptible to eye injuries due to the lack of protective structures around the orbit, including the zygomatic arch. When the zygomatic salivary gland is ruptured or inflamed, causing saliva leakage, it forms a pseudocyst in the posterior part of the orbit, leading to localized inflammation or protrusion of the eyeball (1).

The diagnosis of salivary gland disease is made using various imaging studies such as X-rays, ultrasound, and CT scans. These imaging techniques help assess the condition of the salivary gland by determining whether it is displaced, ruptured, inflamed, or tumored and by identifying the associated ducts. CT scans, in particular, can identify the location and margin of the gland, which is considered essential for surgical planning. Other diseases that may not have been visible on radiographs can also be detected.

It is important to stain the exudate to determine its nature. The exudate produced by salivary gland disease appears yellow to pinkish and is viscous. PAS staining, which is necessary for a definitive diagnosis, is a method that specifically stains polysaccharides such as glycogen, glycoprotein, and mucins. Salivary leakage can be confirmed by staining for mucin, which is present in saliva.

In this case, diagnosis posed a challenge because the patient’s eye had already been removed, and no cyst had formed. Only exudate was observed due to continuous salivary leakage. On CT examination, the right zygomatic salivary gland was dorsally displaced compared to the left and lacked a normal margin. Sialography images confirmed the rupture of the zygomatic salivary gland. H&E and PAS stains were performed to determine the exact component of the exudate. The H&E staining showed only chronic inflammatory cells, with no cells suggestive of a tumor. The positive PAS stain confirmed salivary leakage.

Because the zygomatic salivary gland is located on the ventral side of the eyeball, at the base of the orbit, and medial to the zygomatic arch, zygomatic bone resection is necessary to approach to the gland. Therefore, a dorsal approach is commonly performed to preserve the orbital ligament. Recent studies propose several approaches for managing zygomatic salivary gland issues in brachycephalic dogs: a partial V-shaped ostectomy to minimize resection of the orbicularis oculi, an intraoral approach for the salivary gland, and a ventral approach from the ventral side of the zygomatic arch without bone resection as demonstrated in a cadaver study (3,7,10).

In this case, a ventral approach was performed to minimize resection of the structures, and the ruptured zygomatic salivary gland was successfully removed. Although the salivary gland was dorsally displaced and adhered to the inside of the zygomatic bone, access was possible through a skin incision and masseter muscle retraction. The salivary gland and associated duct were then removed successfully without bone resection.

This case presents a potential cause of surgical site exudate, a complication of enucleation. Current research indicates that the exudate results from substances secreted by the remaining secretory tissues, often leading veterinarians to suspect initial surgery errors. In brachycephalic dogs, however, the zygomatic salivary gland is more susceptible to exposure during surgery. Furthermore, the absence of protective structures postoperatively can render them more susceptible to trauma. Therefore, before considering reoperation, performing cytology through PAS staining and evaluating surrounding structures through a CT scan is essential for effective surgical planning and resolution of complications.

This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through Agriculture and Food Convergence Technologies Program for Research Manpower development funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA) (grant number: RS-2024-00398561).

The authors declare no conflict of interest.