History
A 12-year-old castrated male Quarter Horse was examined because of a puncture wound over the left maxillary sinus ventral to the facial crest. Left nasal epistaxis was noticed the morning of the examination. Physical and oral examinations revealed that the horse also had a firm, movable mass that communicated with the oral cavity. The mass was rostral to the puncture wound. Signs of pain were not elicited during examination. The owner reported that the mass had been evident for approximately 10 years. Digital radiographic images of the skull were obtained (Figure 1).
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Radiographic Findings and Interpretation
On the dorsoventral view, there is an increase in soft tissue opacity involving the left maxillary sinus, which is consistent with post-traumatic hemorrhage and the horse's history of epistaxis (Figure 2). A 4.6 × 3.5 × 3.3-cm mineral opacity, smoothly marginated circular mass is lateral to the left third and fourth maxillary and mandibular premolar teeth. This mass has multiple concentric rings. Multiple small rectangular to ovoid mineral opacities are also in a linear consecutive arrangement along the ventrolateral portion of the left mandible ventrocaudal to the fourth mandibular premolar tooth roots and extending ventrally into the soft tissues. Radiographic findings are consistent with multiple sialoliths.
Comments
A large sialolith was removed surgically. Microscopic examination of the sialolith revealed laminated, diffusely mineralized nonosteoid material with embedded plant material. Cell bodies were not identified. Sialolith formation secondary to the introduction of plant material into the parotid salivary duct was considered the primary differential diagnosis.
Sialoliths develop infrequently in horses. They result from gradual deposition of calcium salt, usually carbonate, around an organic or vegetable nidus that has become lodged in a salivary duct or gland.1,2 The parotid duct is most commonly affected.3,4 Organic nidi are usually cellular debris, resulting from desquamation or inflammatory reaction and bacteria. A vegetable nidus may consist of any small foreign body, such as a grain husk or grass awn, that enters the duct from the salivary papilla.1,2 Because of its slow-growing nature, the calculus is usually unremarkable.1 The classic history, as seen in this case, is an older horse with a firm swelling on the lateral aspect of the head, rostral to the facial crest. Signs of pain are atypical. Obstruction of the duct is usually incomplete, and saliva may continue to pass around the sialolith.3 Large stones may cause obstruction of the duct and salivary retention, which may induce glandular atrophy or acute sialoadenitis with acinar swelling and rupture.1 Definitive treatment is by surgical removal of the sialolith, which yields good results.2,3 Smaller calculi may be massaged out of the parotid papilla.3
- 2.
Murray MJ, Smith BP. Diseases of the alimentary tract. In: Smith BP, ed. Large animal internal medicine. 3rd ed. St Louis: Mosby, 2002;593–653.
- 3.↑
Stick JA. Oral cavity and salivary glands. In: Auer JA, Stick JA, eds. Equine surgery. 3rd ed. St Louis: Saunders Elsevier, 2006;321–351.
- 4.
Baskett A, Parks AP, Mahaffey M. Sialolith and sialoadenitis associated with a foreign body in a mare. Equine Vet Educ 1995;7:309–312.