Surgery of the salivary glands (Proceedings)
Diseases of the salivary glands in dogs are usually inflammatory, neoplastic, or traumatic. Inflammation of the salivary glands is seen occasionally in dogs and cats. If the gland is abscessed, ventral drainage becomes necessary. Infrequently, inflammation or abscess formation can be associated with foreign body migration. In this case, removal of the foreign body with establishment of drainage is indicated. Tumors of the salivary glands are not common in small animals. Salivary gland adenocarcinoma has been reported infrequently. The mandibular and parotid salivary glands are reportedly the most commonly involved with neoplasia in dogs and cats. Mandibular gland adenocarcinoma carry a favorable prognosis with complete surgical removal if metastasis has not occurred. Preoperative chest radiographs and biopsy of the mandibular lymph nodes are indicated in these animals. Parotid salivary gland tumors are more difficult to remove completely and, therefore, have a guarded prognosis. Trauma to the parotid duct from bite wounds is seen occasionally in cats and dogs. A small fistula develops and produces a serous salivary secretion. Simple ligation of the duct proximal to the fistula with 4-0 PDS suture material is an effective treatment, the wound should also be properly drained.
Mucoceles and Ranulas
It is believed that rupture of the sublingual salivary duct results in the formation of a salivary mucocele. The injury may be due to trauma or to unknown causes. These mucoceles, or accumulations of saliva, can occur in various ways. A ranula is a sublingual mucocele. A cervical mucocele is first seen as an external swelling, which may vary in size, in the ventral neck area. A pharyngeal mucocele, develops as a swelling in the pharyngeal wall, and may cause airway obstruction. It may require emergency evacuation and marsupialization. Mucoceles are usually seen as painless, fluctuant swellings. Initially, some pain may exist from tissue irritation by saliva, but this phase is rarely part of the clinical presentation.Diagnosis
The diagnosis of salivary mucocele is not always easy, especially if the swelling has been previously aspirated or injected. In these cases, it may be difficult to differentiate between. a mucocele, tumor and a cervical abscess. Diagnosis should depend on the patients medical history, a complete physical exanimation, and the character of the fluid obtained after aseptic aspiration of the swelling. This fluid may be straw-colored to blood-tinged and is viscid. A consistently effective treatment for cervical salivary mucocele is removal of the affected mandibular and sublingual glandular chain and duct. Therefore, it is necessary to determine on which side the lesion appears. This determination may be obvious, or it may require careful observation and palpation of the mucocele with the animal under anesthesia in dorsal recumbency. Application of pressure to the ventral swelling may also cause the sublingual area to swell and may help to locate the lesion. If the lesion cannot be located physically, sialography by cannulation of the sublingual ducts may be helpful. Leakage from the duct is sometimes demonstrated by radiographic contrast studies Alternately, the mucocele may be incised and evacuated, and the side may be determined by observation of communication between the mucocele and the salivary tissue One may also elect to remove the mandibular, sublingual chains bilaterally without locating the side on which the lesion appears. Sufficient saliva from the zygomatic and parotid salivary glands is present to allow proper chewing and swallowing.
Around the sublingual glandular chain and salivary duct is also conducted in a craniomedial direction. The major blood supply to the mandibular gland is from the glandular branch of the facial artery, which enters the gland where the mandibular duct leaves it. The dorsal part of the deep surface of the gland also accepts branches from the great auricular artery. The major vein also leaves the deep surface of the It is wise to review the important and complex anatomy of the area before performing the operation. The surgical procedure for removal of the mandibular and sublingual salivary glands and their duct requires general anesthesia, wide clipping of the mandibular and cervical areas, and preparation for an aseptic surgery. The dog is positioned in oblique lateral recumbency with a sandbag directly under the proposed incision line. A linear incision is made from the angle of the jaw to where the linguofacial vein and the maxillary vein meet to form the jugular vein. The platysma muscle is divided, and the common capsule of the mandibular and sublingual glands is identified deep to the veins. A branch of the second cervical nerve crosses the capsule and should be preserved. The capsule is opened, and the mandibular gland is grasped with an instrument. Caudolateral traction is carefully applied while sharp and blunt dissection gland. All these major vessels require ligation. The dissection is carried to the digastricus muscle. At this point, if the communication of the glandular tissue with the mucocele is not obvious, the sublingual glandular chain may be passed from lateral to medial beneath the digastricus muscle and the dissection continued rostrally. Care must be taken to avoid injury to the hypoglossal and lingual nerves as well as to the external carotid and lingual arteries. It is not necessary to remove the mucocele, which is technically a foreign body granuloma, because it does not have a secretory epithelial lining. A quarter-inch Penrose drain may be placed to drain both the primary incision and the mucocele. Closure consists of absorbable interrupted sutures in the platysma muscle or subcutaneous tissue, and skin closure. The drain may be removed in 3 to 5 days. Complications can include seroma formation, and local infection.