Page 108 - Atlas of Small Animal CT and MRI

1.7

Salivary glands

Introduction enters the oral cavity at the level of the sublingual carun-
cle. The zygomatic duct enters the oral cavity caudal to
The salivary glands include the mandibular, zygomatic, the parotid duct at the level of the first upper molar and
parotid, and lingual glands. The mandibular salivary often has several diverticula. 2
gland is a large, oval, uniform structure located caudal
to the mandible. On CT images it has a uniform texture
(Figure 1.7.1). The parotid salivary gland is thin, elon- Inflammatory disorders
gated, and has a finely textured lobular structure. It is Zygomatic sialadenitis is an inflammatory condition of
located lateral to the vertical ear canal and cranial and the zygomatic salivary gland. The position of the gland
dorsal to the mandibular salivary gland. The parotid and in the ventrolateral orbit causes secondary exophthalmos
mandibular salivary glands are moderately hyperintense when enlarged and inflamed. CT and MR imaging show
to muscle on T1 images, but the mandibular salivary gland an enlarged, hypoattenuating (CT) and T1 hypointense,
is hyperintense to the parotid on T2 images (Figure 1.7.2). T2 and FLAIR hyperintense (MR) gland with surround-
The zygomatic salivary gland is variable in size and shape, ing loss of detail due to inflammation (Figures 1.7.5, 1.7.6).
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and it is located in the orbit, lateral to the pterygoid The disease is usually unilateral but can also be bilateral.
muscles and ventral to the globe (Figure 1.7.3). Contrast Formation of fluid‐attenuating or T2 hyperintense
enhancement on CT is slightly heterogeneous because of sialoceles is common. The mandibular and parotid sali-
the glandular architecture. The major sublingual salivary vary glands are occasionally affected by sialadenitis. This
gland is fused to the cranial capsule of the mandibular appears on CT images as enlargement of the gland lateral
salivary gland. It appears triangular in shape in the sagittal and ventral to the ear canal (Figure 1.7.7). Affected
plane (Figure 1.7.1) and may be more difficult to visualize glands are intensely contrast enhancing and often retain
on MR images. Glands are isointense to hyperintense to their glandular structures, including ducts, despite the
adjacent musculature on T1 and hyperintense on T2 inflammatory change. The structure may become dis-
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images (Figure 1.7.4). The salivary glands moderately to rupted with sialocele or abscess formation (Figure 1.7.8).
intensely contrast enhance on both CT and MR images.
Sialography of the salivary glands using CT has been
performed in cadavers by placing a cannula and Neoplasia
extension set in the oral salivary duct. Diluted nonionic Tumors of the salivary glands are uncommon. These
contrast medium mixed with methylcellulose was used lesions produce mass effect in the regional tissues of the
to fill the ducts. The parotid duct travels from the rostral head and irregular enlargement of the gland of origin.
and ventral border of the gland, lateral to the masseter Contrast enhancement may be strong to heterogeneous
muscle, to the level of the 4th premolar. The mandibular if there is fluid present or regions of necrosis. Tumors
duct travels medial and parallel to the mandible and can be differentiated from sialadenitis by the disruption

Atlas of Small Animal CT and MRI, First Edition. Erik R. Wisner and Allison L. Zwingenberger.
© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.
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