Sialoceles are not common in dogs and are even rarer in cats. A sialocele is an abnormal accumulation of saliva, resulting in a compressible swelling in the neck. Another term that has been used to describe this condition is salivary mucocele. However, since our veterinary patients produce a combination of mucous and serous salivary secretions, sialocele may be a more appropriate term.1 This disease occurs most commonly in dogs, and its etiology is thought to be a result of trauma to the duct of a monostomatic gland, resulting in extravasation of saliva into the subcutaneous and submucosal tissues with formation of a pseudocyst. However, ineffective attempts to experimentally create sialoceles2 and breed predilections (poodles)1 suggest other factors, such as genetics, may play a role. I have seen a few cases of sialoceles in dogs with concurrent sialoliths: the rough surface of sialoliths may irritate and cause damage to the duct system. Especially if the sublingual gland is involved, a ranula (sublingual sialocele) may occur in conjunction with, or in the absence of, a cervical sialocele. Palpation is a very helpful diagnostic tool, and aspiration of the swelling can be done to obtain more information. Aspiration of a sialocele produces a straw-colored or blood-tinged viscous fluid. This fluid may be submitted for cytology, but the consistency and appearance of the fluid are very telling. Repeated aspiration in attempts to drain the fluid is rarely beneficial and is not recommended since saliva is produced at such a rapid rate; any beneficial results of aspiration are usually transient. Tully’s tale I would like to share a case with you I saw 18 months ago. “Tully,” a seven-year-old male neutered goldendoodle, was presented to his primary care veterinarian for drooling, halitosis, and lethargy that had started two days prior. Oral examination revealed a swelling under the left side of the tongue, odor from the mouth, and a 7 cm x 5 cm x 4 cm fluctuant swelling in the left neck (Figures 1A and 1B). Tully, a seven-year-old goldendoodle, presented with A) sublingual and B) left neck swelling. Photos courtesy Dr. John R. Lewis The neck swelling was aspirated by Tully’s primary care vet, which showed a clear viscous fluid. Though lethargy and odor are rarely seen with sialoceles, everything else supported the diagnosis of cervical sialocele. An antibiotic and carprofen were prescribed by Tully’s primary vet, with no change to the swelling. Tully was referred to me and scheduled for a cone-beam CT scan and removal of the mandibular and sublingual salivary glands on the left side. Though cone-beam CT is not as definitive for assessment of soft tissue lesions as it is for bony and dental lesions, the radiologist’s report of the CT documented a left ventral cervical fluid-filled mass lesion, most consistent with a cervical sialocele, and small mineral-attenuating foci consistent with sialoliths. The swelling was causing compression and rightward displacement of the larynx. Mild left medial retropharyngeal lymphadenopathy was also noted, which was thought to be reactive. Surgery was performed via a skin incision in the neck. The mandibular and sublingual glands were dissected with the intent to remove the entire mandibular and monostomatic portion of the sublingual gland (Figure 2A). A Penrose drain was placed and removed four days later. A) Tully’s first surgery involved the removal of the mandibular and sublingual salivary glands through the neck. B) After recurrence of the sialocele, an intraoral approach wasmade to follow the salivary ducts caudally. Photos courtesy Dr. John R. Lewis A persistent problem Tully’s subsequent rechecks went well, and there were no signs of recurrence. However, 11 months later, Tully was presented with a fluctuant swelling in the left neck area of 4 cm in diameter. Aspiration was consistent with saliva. A second surgery was performed, and this time, an intraoral approach was performed to follow the ducts of the sublingual and mandibular salivary glands to hopefully remove any remnants of the sublingual gland (Figure 2B). Dissection of the duct system did not lead us to a fluctuant pocket of saliva, so an exploratory through the neck incision was also performed during the same procedure. A possible remnant of salivary tissue was identified and submitted for histopathology. Histopathology showed granulomatous and neutrophilic inflammation and fibroplasia, with no evidence of neoplasia or glandular tissue. At Tully’s two-week healing recheck, no evidence of sialocele recurrence was seen, but four months later, a fluctuant left neck swelling recurred. A conventional CT scan was recommended. The conventional CT scan was done at Ryan Veterinary Hospital at the University of Pennsylvania, which ensured saliva was not arising from another salivary gland, such as the parotid or zygomatic gland. CT also identified a possible remnant of sublingual salivary gland, which was approximately 9 mm wide (Figure 3). Axial image from a conventional CT scan with contrast, showing a possible salivaryremnant medial to the digastricus and ventral to the carotid artery. Photo courtesy Dr. John R. Lewis After discussing the situation with Tully’s owners, oral surgeons, soft tissue surgeons, and a radiation oncologist, the owners decided to pursue radiation therapy targeted at the salivary remnant due to concerns that further surgery would be akin to finding a needle in a haystack. Radiation treatment Salivary tissue is very sensitive to radiation, as evidenced by xerostomia that people experience after head/neck radiation. Radiation as a treatment for recurrent sialoceles has been documented in a 2018 manuscript in the Journal of Veterinary Internal Medicine. This manuscript acknowledges that surgery is the first line of treatment, but with a recurrence rate of 5-14 percent3 and the inherent sensitivity of salivary tissue to radiation, its use for treatment of recurrent sialoceles may be reasonable. The study had a median follow-up of 17 months, and due to the retrospective nature of the study, there were varied total doses (12-20 Gy). Of the 11 dogs in the study, six dogs (54 percent) achieved a complete response (CR), and five dogs (45 percent) achieved a partial response (PR).4 Tully had a consultation with Thomas Lee, DVM, DACVR, at Penn Vet’s Radiation Oncology Service, and he will begin treatment around the time I write this. If you’ve had a patient with a recurrent sialocele and how you dealt with it, email me at info@siloacademy.com. John R. Lewis, VMD, DAVDC, Fellow, AVDC OMFS, practices at Veterinary Dentistry Specialists and teaches at Silo Academy Education Center, both in Chadds Ford, Pa. References Lane JG. Surgical treatment of sialoceles. In: Verstraete FJM, Lommer MJ. Oral and Maxillofacial Surgery in Dogs and Cats. London: Saunders Elsevier; 2012. p 501-510. DeYoung DW, Kealy JK, Kluge IP. Attempts to produce salivary cysts in the dog. Am J Vet Res. 1978;39:185-186. Benjamino KP, Birchard SJ, Niles JD, et al. Pharyngeal mucoceles in dogs: 14 cases. J Am Anim Hosp Assoc 2012;48:31–35. Poirier VJ, Mayer-Stankeová S, Buchholz J, Vail DM, Kaser Hotz B. Efficacy of Radiation Therapy for the Treatment of Sialocele in Dogs. J Vet Intern Med. 2018 Jan;32(1):107-110.
