Disorders of the salivary gland in dogs and cats have received only very little attention, with less than a 1% documented prevalence. Common salivary gland disorders in dogs and cats include sialadenitis, salivary mucocele (commonly called sialocele), neoplasm, and various degenerative or fibrotic lesions [1,2]. Salivary mucocele (sialocele) results from the accumulation of saliva secondary to salivary gland or duct obstruction and traumatic injury. Although any dog breed or other animals can be susceptible to salivary mucocele [3–7], it has been documented more in young male dogs with Poodles and German Shepherds breeds mostly affected. Sialoceles are classified based on their anatomical location as sublingual, cervical, pharyngeal, zygomatic, or complex sialoceles. The sublingual/mandibular gland and duct complex are the most commonly affected structures [1–4]. Sialoceles are usually asymptomatic, but with an increase in size, they cause discomfort serving as stressor with symptoms such as oral bleeding, chewing-related trauma, respiratory distress, and dysphagia, depending on their location. Some clinical observation studies revealed that dogs presenting with sialocele often have underlying conditions such as hypercortisolism or have been subjected to prolonged duration of treatments with glucocorticoids which compromise salivary gland function dangerously reducing the pH while increasing the viscosity and respectively causing corrosion effect and accumulation of saliva [4,8].

The clinical presentation depends on the location, for instance, a cervical sialocele usually appears as a slowly enlarging non-painful swelling in the intermandibular area. The sublingual salivary gland is the most commonly affected with the presentation of mucocele cavities lined by granulation tissue rather than the epithelial lining. Other commonly affected sites are the cervical, intermandibular, and pharyngeal or zygomatic tissues [5,7,9,10]. Diagnosis is by comprehensive clinical examination involving assessment of clinical parameters of body temperature, pulse rates, and respiratory rates. Also, physical examination by palpation of affected body surfaces for consistency, texture, and content assessments, fine needle aspiration for exfoliative cytology examination, sialography of the salivary glands, ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT) [10,11–14]. Drainage of the mucocele via needle aspiration has been employed over the years, with recurrence as a major setback to achieving a cure. The aspirates usually reveal a transparent viscous mucoid fluid, sometimes slightly bloody or cloudy fluids [15]. Surgical incisions into the affected salivary glands have sometimes resulted in a cure although the removal of the entire salivary gland ductus complex has significantly reduced the rate of recurrence even though the need for complete pseudo-capsule resection is still under debate [4,10]. Therefore, this case report of sublingual salivary mucocele in a Russian shepherd dog in Jos, Nigeria can serve as a reference in the definitive management of uncomplicated salivary mucocele.

A diagnosis of sublingual salivary Mucocele was established based on historical and clinical evidence. In line with established surgical principles documented in Fossum [16], the dog fasted for 12 hours before surgical management to avoid complications from anesthetic effects. Following the aseptic preparation of the patient and anesthesia achieved using 1% atropine sulfate (Atropine^®—Shanxi Shuguang Pharmaceutical Co., Ltd., Qixian China) IV as pre-anesthetics and 50 mg/ml Ketamine hydrochloride (Jawa ketamine^®—Swiss Parenterals Ltd., Gujarat, India) + 2% Xylazine (Alfasen, Woerden-Holland) IV as induction and maintenance anesthetics. The bitch was placed on left lateral recumbency, with the mouth kept open using a self-retaining retractor, and the tongue was reflected to expose the soft tissue swelling (mucocele) and surgical field toward the right side, adjacent to the frenulum. The swelling and immediate surroundings were thoroughly cleaned with an antiseptic solution (dilute Chlorhexidine) to decontaminate the surgical field or at least reduce bacteria load from the site. Using a size 23 scalpel blade, a circumscribed incision was made around the mass. The mucocele with the sublingual salivary gland and duct was excised while the microvascular bleeders around the resulting defect were arrested by compression using adrenaline-soaked gauze. Ligatures were placed using size 0 Polyglactin 910 (synthetic absorbable suture material) for larger blood vessels and the resulting defect in the surgical site was reconstructed in a simple continuous suture pattern using a Polyglactin 910. It was ensured that a tiny gap was left for drainage of tissue fluids so as to prevent seroma formation (Fig. 1B—1F).

The excised tissue was sent for histological evaluation which was routinely stained with hematoxylin and eosin (H and E). The prepared slide was then examined under a light microscope (Olympus Research microscope, CH20i binocular version, Shinjuku, Tokyo, Japan, with AmScope 10MP USB microscope digital camera + calibration kit, Mainland, China) with objectives 100x and 400x (Fig. 2). A histological diagnosis of Sublingual salivary mucocele was reached by the pathologists at the Veterinary Teaching Hospital, University of Jos. Also, a swab of the surgical site was collected and sent to the microbiology laboratory for microbial culture and antibiotic susceptibility testing.

Post-operatively, the dog was placed on intravenous fluids (Ringers Lactate solution^® and 50% dextrose) followed by the provision of a bland/gruel diet for 3 days before the re-introduction of the normal food. Also, injectible (inj.) 200,000 iu Penicillin 12,000 iu/kg and 200 mg Streptomycin 20 mg/kg IM × ⁵/₇, Inj. 10 mg Piroxicam 0.3 mg/kg IM × ²/₇ Q 48 hours. and Inj. vitamin B complex IM × ²/₇, was administered. Daily assessment and monitoring of the surgical site was carried out for the first 5 days ensuring no secondary bacteria or any other complications of any sort resulted. Thereafter, the examination was done twice weekly with the vital signs routinely assessed. The wound was judged to be fully healed 3 weeks post-operation and the dog was completely discharged after 1 month of monitoring with no evidence of recurrence.

In this study, the diagnosis was relatively simple and similar to the majority of reported cases as the aseptic aspirates from the swelling revealed a viscous, clear fluid consistent with saliva having a small to moderate number of non-degenerated nucleated cells and diffused aggregates of mucin which was consistent with sublingual sialocele [1–4]. It is not unusual to have a collection of mucoid saliva leaked from a damaged sublingual salivary gland duct. Although salivary gland disorders are rarely diagnosed especially in animals, sialocele is the most common amongst all the salivary gland disorders. The history of being fed with lots of bones, in this case, gives credence to the submission by Sutradhar et al. [17] that the presence of few teeth makes it possible for bones, especially those with sharp edges to cause crushing or piercing injuries to the sublingual salivary gland resulting in tears with leakage of saliva into the surrounding tissue [17]. As in this case, an increase in the size of the mucocele interfered with the ability to feed, resulting in malnourishment if left unattended for a prolonged period [4].

Although sialography is an accurate modality for identifying the salivary gland involved, MRI and CT have almost completely replaced sialography due to their superior benefits of displaying the relationship of the lesions with the surrounding tissues [11–14]. In this case, it was impossible to clinically define the side of the affected sublingual/mandibular salivary gland involved because at the time of the case management, a CT scan was not available at the Veterinary Teaching Hospital. The decision to surgically excise the sialocele (sialoadenectomy) was in agreement with reports by Pozzobon et al. [10] and Gokulakrishnan et al. [9] where they reported surgical excision of the gland as the preferred management option as it is usually definitive with no associated recurrence as observed in aspiration. Also, the choice of the surgical approach was, for the most part, based on the location of the saliva collection. Even though the ventral approach of sialoadenectomy is preferred by some clinicians as it permits easier removal of the entire sublingual gland-duct complex, we undertook the lateral approach. The decision of the lateral approach was to lower the risk of wound-related complications that may necessitate a bilateral sialoadenectomy [18,19]. The complete excision of the capsule and associated duct which left no remnants behind, while minimizing excessive tunneling under the digastricus muscle was also possible via a lateral approach before closure was made using a simple interrupted suture with a drainage space left behind [19,20]. The negative microbial culture of the swab taken from the pseudocapsule of the sialocele confirmed the non-infectious origin of the sialocele in this case [21–23].

Microscopic examination of the mucocele tissue section revealed a dilated duct lined by squamous epithelium, and sub-epithelial fibrosis; dense populations of cells with clear cytoplasmic vacoulations and delicate capillary networks [11,13]. These corroborate the findings by Sravanti et al. [5] in which they reported the changes to include- acinar atrophy, dilated ducts, periductal hyalinization, interstitial lymphoplasmacytic infiltration in salivary gland parenchyma, and the proliferation of granulation tissue along with fibrosis [6].

The majority of recorded case series are conducted retrospectively. However, we have given a clinical salivary Mucocele case report that, to the best of our knowledge, is representative of a typical instance. Our goal is to increase awareness and information regarding the treatment of sialocele, which may be completely resolved with surgical excision.

The author appreciates the immense contributions of Mr. G. James of the Pathology Department, Plateau Specialist Hospital, and Mr. Y. I. Abdulkareem of the Veterinary Biochemistry, Physiology, Pharmacology and Toxicology Department, University of Jos, Plateau state for assisting with the laboratory analysis.

The authors declare they have no conflict of interest.

AVAZI, Daniel Onimisi had full access to all of the data in the study and takes responsibility for the integrity and accuracy of the data. D. O. Avazi, P. I. Sambo, A. Aliyu, and J. J. Kalang were involved in the Case Management, D. O. Avazi, G. Y. Gurumyen, and O. Orakpoghenor, handled the processing as well as interpretation of cytology and histology. D. O. Avazi was responsible for the write up with all authors contributing by way of proofreading, editing, and approval of the final manuscript.