Salivary Fistula

Description

A salivary fistula can result from injury to any salivary gland, but most commonly the parotid. Fistulas forming from other glands is uncommon. 

Injury may be due to traumatic wound to the face e.g. bite wound or abscess drainage. Exopthalmus is the most likely cause of a zygomatic fistula.

The continuous flow of saliva prevents healing and therefore a fistula develops

When a salivary duct injury occurs due to trauma on the face, this results in a fistula being created which will cause discharge of saliva onto the face. Discharge from the gland may be noticably worse before or during feeding.

Diagnosis

Clinical Signs

A fistula can often be located over the parotid region upon clinical examination and this is usually highlighted by the presence of discharge coming from this area.

There is often history of a wound over the parotid region.

Differentiation from a draining sinus by assessment of the discharge- salivary fistula will discharge a golden or blood tinged saliva, which will be viscous and 'stringy' in appearance. Mucous can be identified in this by use of periodic acid-schiff stain if neccesary.
 

Treatment

Surgical ligation of the duct proximal to the injury will usually resolve the problem (complete removal of the gland can be performed if neccesary). Removal of the parotid gland is not usually performed due to high risk of complications such as cranial nerve trauma.

Skin is incised over the duct on side of face (beware of buccal nerves) and a wide diameter suture material can be used to cannulate the duct in order to aid locating it during surgery.
Occasionally a mucocele may develop from the site of surgery.

References

Ettinger, S.J., Feldman E.C. (2000) Textbook of Veterinary Internal Medicine 5 th Ed

Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier
Merck & Co (2008) The Merck Veterinary Manual