Zygomatic sialolithiasis diagnosed with computed tomography in a dog

Abstract

A 10-year-old castrated Shih-Tzu male dog was referred for examination of acute right exophthalmos, protrusion of the third eyelid and soft tissue swelling ventral to the globe. Ultrasonography revealed echogenic fluid around the right globe. Computed tomography (CT) showed an enlarged right zygomatic salivary gland compared with the left zygomatic gland and an amorphous cystic mass ventral to the right globe. Hyperdense material, which we suspected to be a sialolith, was identified in the right zygomatic gland. The zygomatic gland and the cystic lesion were removed, and a zygomatic sialocele with sialolith and ductal obstruction were found by histopathological examination. CT was a useful diagnostic tool for zygomatic sialolithiasis.

Fig. 1.

Dorsoventral view (A) and right lateral view (B) of skull radiographs show protrusion of right eye (arrows). There are not severe bony changes by skull neoplasia and remarkable periodontitis.

Fig. 2.

Ocular ultrasonography. Cyst-like structure (c) with amorphous hyperechoic material (asterisk) appears around the right retrobulbar region.

Fig. 3.

Computed tomography (CT) of skull. Transverse CT images before (A, C) and after (B, D) contrast medium administration show cystic materials (c) around right globe and zygomatic gland (asterisks). The right zygomatic gland (arrow) has small cystic lesions (arrow) and a focal hyperdense object (dashed arrow).

Fig. 4.

Histopathological (HE stain) results of the right zygomatic gland. (A) Extrusion of the mucinous (arrows) from the salivary gland into the adjacent connective tissue. (B) A large mineralized structure (asterisk) occluding one of ductal cavity.