Page 792 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.1 The upper gastrointestinal tr act 767

VetBooks.ir to prevent its ejection during normal mastication. extremely painful disease and affected patients are
dysphagic and painful to palpate.
Permanent stenosis of the duct causes chronic dis-
tension and mucocoele formation.
Diagnosis
SIALOADENITIS (PAROTIDITIS) History and clinical signs are often diagnostic.
Ultrasonography is useful to diagnose the distended
Definition/overview ducts and affected glands. CT should be considered
Inflammation of the salivary glands or ducts. in chronic cases.

Aetiology/pathogenesis Management
Transient inflammation of the salivary gland can Most cases resolve spontaneously when the horse is
occur following trauma to the gland or after duct removed from the pasture, provided that the duct
obstruction, but is uncommon. This phenomenon is unobstructed. Chronic septic sialoadenitis can be
may be observed in grazing horses in Europe and treated using salivary lavage and attempts to encour-
Australia, particularly in the early growing season, age drainage via the parotid duct, plus antimicrobial
but it appears to be rare in the USA. therapy based on culture and sensitivity.

Clinical presentation NEOPLASIA
The glands are bilaterally swollen but are non-
painful a few days after grazing at pasture. It does Neoplasia affecting the salivary gland is rare.
not affect mastication, appears to be a response to Adenocarcinomas, acinar cell tumours and mixed cell
changes in the content of grazed forage and is sea- carcinomas have been reported. Enlargement of the
sonally self-limiting. It may occur sporadically or parotid gland associated with advanced melanoma
as a herd outbreak. Chronic cases of parotiditis can is not uncommon in grey horses, and the swelling
develop salivary gland abscessation due to infection may be sufficiently large to impinge into the phar-
with pyogenic organisms (Fig. 4.93). This is an ynx and restrict airflow in extreme cases (Fig. 4.94).

4.93 4.94

Fig. 4.93 This horse has gross distension of the Fig. 4.94 Enlargement of the area immediately
parotid gland (arrows) due to an acutely painful caudal to the left vertical mandible caused by a
bacterial infection. number of large parotid gland melanomas.