Page 790 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.1 The upper gastrointestinal tr act 765

VetBooks.ir TRAUMA TO SALIVARY 4.90
GLANDS AND DUCTS

Definition/overview
Parotid duct trauma is the most commonly encoun-
tered salivary disorder. The parotid salivary gland
lobules drain via multiple small ductules, which con-
verge and anastomose to form the parotid duct. This
passes ventrally on the medial side of the mandible,
before traversing its lateral border to ascend rostral
to the masseter muscle, before entering the oral cav-
ity via the parotid papilla at the level of the 3 cheek
rd
tooth.

Aetiology/pathophysiology
Trauma to the parotid duct can result from kicks to Fig. 4.90 This view of the right side of the face of
the mandible, lacerations, surgical treatments includ- a pony shows a marked swelling in the centre of the
ing dental extraction and guttural pouch surgery. clipped area due to a salivary mucocoele under the
skin (arrow). (Photo courtesy Graham Munroe)
Clinical presentation
The most common location of parotid duct damage 4.91
is on the ventral aspect of the mandible where the
duct passes from the medial to the lateral aspects.
Small wounds to the duct lead to saliva leakage with
staining of the hair in some cases, which is usually
short-lived and resolves spontaneously after a few
days as the duct heals by granulation. If a large vol-
ume of saliva is continuously draining, a salivary fis-
tula can develop, or if the skin heals but the duct
does not, a salivary mucocoele (Figs. 4.90, 4.91).

Diagnosis
The clinical appearance and production of saliva in
response to stimulation of food is normally diag-
nostic. Retrograde contrast radiographs have been
attempted.

Differential diagnosis Fig. 4.91 Transcutaneous ultrasound image of
Sinus tracts due to foreign body penetration, dentig- the mucocoele shown in 4.90. Note the loculated
erous cysts, tooth root infections. hypoechoic well-described fluid swellings
overlying the hyperechoic bone of the jaw.
Management (Photo courtesy Graham Munroe)
Wounds to the parotid gland usually heal by gran-
ulation. When surgical debridement is indicated, salivary stimulation can be attempted, albeit gen-
care should be taken to avoid iatrogenic damage erally with limited success. Fistulae resulting from
to branches of the salivary duct. The withholding trauma to the gland similarly heal by granulation in
of feed and feeding via a nasogastric tube to reduce most instances.