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Diagnosis: Enlarged Parotid Gland

Filippone, Lisa M. MD

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Dr. Filippone is an assistant professor of emergency medicine at Drexel University College of Medicine and the director of the Division of Emergency Ultrasound at Mercy Hospital of Philadelphia.

This patient has an enlarged right parotid gland. She recently had been diagnosed with chronic lymphocytic leukemia, and her parotid gland became enlarged secondary to proliferation of lymph tissue within the parotid.

The paired parotid, submandibular, and sublingual glands are referred to as the major salivary glands. The parotid is the largest of the salivary glands. The majority of the parotid gland lies superficial to the masseter muscle, caudal and ventral to the external auditory canal, but a portion extends deeper around the angle of the mandible through the stylomandibular tunnel.

Stensen's duct emerges from the anterior parotid gland and runs ventrally along the masseter muscle until is turns medially to pierce the buccinator muscle. Its opening can be visualized on the buccal mucosa at the level of the upper second molar. The main trunk of the facial nerve enters the posterior aspect of the parotid and subsequently divides within the gland into the temporal, zygomatic, buccal, mandibular, and cervical branches.

During embryonic development of the parotid gland, lymph tissue becomes incorporated within the parenchyma itself. Later when the parotid gland is encapsulated, periparotid lymph nodes also are included, and both the intraparotid and periparotid lymph nodes are located within the gland. While lymph tissue may be found in the other salivary glands, it is by far more common and more organized within the parotid gland.

The submandibular gland is the next largest of the major salivary glands. It is located in the submandibular triangle of the neck, and is essentially folded around the mylohyoid muscle. Wharton's duct emerges from the gland, and courses upward to open on the floor of the mouth on the sublingual papilla.

The sublingual gland is the smallest of the major salivary glands, and is located just below the sublingual mucosa of the floor of the mouth. It usually does not drain into a single duct but rather multiple ducts referred to as the ducts of Rivinus, open onto the floor of the mouth. There also are approximately 750 minor salivary glands located beneath the mucosa of the oral cavity, palate, pharynx, larynx, and paranasal sinuses.

Disease processes that may affect the salivary glands generally can be grouped into acute inflammatory disorders, chronic inflammatory disorders, and neoplastic disorders. Acute inflammation of the salivary glands may be secondary to viral infection, bacterial infection, or by obstruction by a ductal calculus. The most common viral infection of the parotid gland is due to paramyxovirus (mumps), but coxsackie, echovirus, parainfluenza I and III, the herpes viruses, and influenza A are not uncommon. Patients typically present after several days of malaise, fatigue, and fevers with bilateral parotid gland enlargement, which is painful especially during mealtime. The gland may be enlarged and tender, but it is rarely erythematous or warm. Treatment is symptomatic with antipyretics and anti-inflammatory medications.

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In contrast to viral sialadenitis, acute suppurative sialadenitis usually presents with sudden onset of salivary gland enlargement, often unilateral and involving the parotid, which is tender, warm, and erythematous. Fever may not be present initially, but may develop if the infection is left untreated. Purulent material may be expressed from the duct when the gland is massaged. The classic patient at risk for acute bacterial sialadenitis is one who is status post-abdominal surgery and NPO. The reason for this is that the major contributing factors to its development are dehydration and decreased salivary flow.

Other risk factors include any process that obstructs salivary flow such as ductal structures, calculi, and oral neoplasms. With decreased salivary flow, oral pathogens can travel retrograde into the duct and parenchyma of the gland, resulting in infection. Streptococcus viridans, Staphylococcus aureus, Streptococcus pneumoniae, and Hemophilus influenza are the most common pathogens isolated, although anaerobes are not uncommon. Treatment includes hydration, gland massage, sialagogues, and antibiotics. CT scan may be done to look for the presence of calculi or to rule out abscess, which would require surgical drainage. Typically it is not required unless there is no clinical improvement with standard therapy. Complications include extension into the parapharyngeal spaces and other deep neck spaces with possible airway obstruction and sepsis.

Unlike sialadenitis, which typically involves the parotid glands, sialolithiasis typically involves the submandibular glands. Patients present with unilateral pain and swelling of the affected gland. Palpation of a calculus may be possible if it is located in the distal duct, in which case treatment involves removal of the stone transorally. If the stone is located in the proximal duct or within the gland, excision of the gland is often required.

Chronic inflammatory disorders include a heterogeneous group of disease processes usually involving the parotid glands that result in recurrent painful glandular enlargement. Infectious granulomatous diseases such as tuberculosis, cat scratch fever, syphilis, and other atypical mycobacterial infections have been described as causes of chronic parotid enlargement. Sarcoid may involve the parotid gland in approximately 10 percent to 30 percent of patients, and may be the initial clinical manifestation. Autoimmune diseases involving the salivary glands include the well described Sjogren's syndrome, which usually presents with keratoconjunctivitis sicca, and xerostomia, with or without other connective tissue involvement. Cyst development within salivary glands may result from a multitude of causes including prior infection, trauma, or radiation or in association with neoplasm or systemic illnesses. Patients with HIV infection may present with bilateral parotid lymphoepithelial cysts.

The majority of neoplastic disorders that involve the salivary glands are benign, with the parotid gland most commonly affected. Pleomorphic adenoma, often referred to as benign mixed tumor and Warthin's tumor, are the most common neoplasms of the salivary glands. While both are usually benign, malignant transformation may occur. Treatment is surgical excision. In children, hemangiomas are the most common parotid tumors. These usually undergo spontaneous involution. Malignant tumors of the salivary glands include mucoepidermoid carcinoma and adenoid cystic carcinoma, with the former most commonly seen in the parotid gland and the latter in the submandibular gland.

As mentioned previously, the salivary glands and in particular the parotid glands contain lymph tissue that may proliferate secondary to reactive or neoplastic disease. Malignant lymphomas of the salivary glands may arise de novo or in association with prior lymphoproliferative disorders. In the patient pictured, the parotid gland enlargement was secondary to her chronic lymphocytic leukemia. A CT scan was done which confirmed local involvement of the right parotid gland with no signs of parapharyngeal extension or airway occlusion. In consultation with her oncologist, she was discharged to follow-up with him as well as with ENT.

© 2004 Lippincott Williams & Wilkins, Inc.