Chronic parotitis

1. Cause and Etiology

Chronic parotitis is a long-standing inflammatory condition of the parotid gland, which is the largest of the major salivary glands. It results from recurrent or persistent inflammation and can lead to progressive glandular destruction and dysfunction.

Etiologic Factors:

Obstructive causes:

Sialolithiasis (salivary stones)
Ductal strictures or stenosis
Mucus plugs

Infectious causes:

Bacterial infections (commonly Staphylococcus aureus, Streptococcus spp.)
Recurrent viral infections (e.g., mumps)

Autoimmune diseases:

Sjögren’s syndrome – chronic autoimmune lymphocytic infiltration
IgG4-related disease

Radiation-induced sialadenitis – after head and neck radiation therapy
Idiopathic – in many cases, no clear cause is found

2. Pathophysiology

The pathophysiology of chronic parotitis involves recurrent inflammation that leads to:

Glandular damage → destruction of acinar cells (functional saliva-producing units)
Fibrosis and atrophy of glandular tissue
Lymphocytic infiltration (especially in autoimmune forms)
Ductal obstruction → leading to saliva stasis, promoting infection and further inflammation
Sialectasis (dilation of the salivary ducts)

This leads to a vicious cycle of stasis, infection, inflammation, and tissue damage.

3. Epidemiology

Age: Affects both children and adults, but is more common in middle-aged and elderly adults
Sex:

Slight female predominance in autoimmune-related cases

Geographical:

No specific geographic predilection, but autoimmune forms may be more common in Western populations

4. Clinical Presentation

Patients with chronic parotitis typically present with:

Recurrent or persistent swelling of the parotid gland

Often unilateral, but can be bilateral (especially in autoimmune diseases)

Pain or tenderness, often exacerbated during meals
Dry mouth (xerostomia) – especially in autoimmune types
Pus discharge from the Stensen’s duct upon massage
Firm or nodular gland on palpation
Low-grade fever during acute exacerbations
Recurrent episodes of acute sialadenitis with progressive glandular dysfunction

5. Imaging Features

Several imaging modalities are used to assess chronic parotitis:

Ultrasound:

Heterogeneous echotexture
Hypoechoic areas (sialectasis)
Increased gland size or atrophy
Ductal dilatation
May detect sialoliths (calcified stones)

Sialography (less commonly used now):

"Sausage-link" appearance: alternating dilated and narrowed ducts
Sialectasis
Ductal obstruction or stenosis

MRI / MR Sialography:

Non-invasive visualization of the ductal system
Useful for detecting siallectasis, glandular fibrosis, and inflammation

CT Scan:

Shows calcifications (stones)
Glandular enlargement or atrophy
Used for surgical planning or when malignancy is suspected

6. Treatment

Treatment depends on the underlying cause and severity of the disease.

Conservative Management:

Hydration
Sialogogues (lemon drops, sour candies to stimulate saliva)
Massage and gland milking
Good oral hygiene
Antibiotics for acute infectious episodes

Medications:

Anti-inflammatory agents (NSAIDs)
Corticosteroids (especially in autoimmune etiologies)
Immunosuppressants (e.g., hydroxychloroquine in Sjögren’s)
Anticholinergic agents should be avoided as they reduce saliva

Interventional/Surgical:

Ductal dilation or sialendoscopy to relieve obstruction
Stone removal if present
Parotidectomy (partial or total) in severe, refractory cases with significant gland damage

7. Prognosis

Variable prognosis depending on cause and response to therapy
Mild forms (e.g., obstructive sialadenitis) may resolve with conservative treatment
Chronic autoimmune parotitis often progresses despite treatment, leading to:

Persistent xerostomia
Dental caries, oral infections
Increased risk of non-Hodgkin’s lymphoma in Sjögren’s syndrome

Surgical treatment can provide definitive relief, but may carry risks (facial nerve injury)

Summary Table

Aspect	Description
Cause	Obstruction, infection, autoimmune, idiopathic
Etiology	Sialolithiasis, Sjögren’s, bacterial/viral infections
Pathophysiology	Ductal obstruction → inflammation → fibrosis & acinar loss
Epidemiology	More common in middle-aged/older adults; slight female predominance
Clinical Signs	Recurrent swelling, pain, pus discharge, dry mouth
Imaging	Heterogeneous echotexture, sialectasis, ductal changes
Treatment	Hydration, antibiotics, sialogogues, steroids, surgery
Prognosis	Good with conservative care in mild cases; variable in autoimmune forms

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Case study: A 38-Year-Old Woman with Dry Mouth and Bilateral Cheek Firmness

Chronic Parotitis

History and Imaging

A 38-year-old woman presented with xerostomia (dry mouth) and mild stiffness in both cheeks.
Her medical history was significant for thyroid cancer, thyroidectomy, and radioactive iodine ablation therapy performed the previous year.
Since then, her symptoms of dry mouth have gradually worsened.
Shown below are images from a salivary gland scintigraphy study. Please refer to the whole-body scintigraphic images taken at 1, 10, and 40 minutes, along with a summary image displaying the counts per unit time in the parotid and submandibular glands following lemon juice stimulation.

Quiz 1

What is the key finding on the salivary gland scintigraphy?
(1) Radiotracer uptake, trapping, and excretion are normal in both parotid glands.
(2) Radiotracer uptake, trapping, and excretion are abnormal in both parotid glands.
(3) Radiotracer uptake, trapping, and excretion are abnormal in both submandibular glands.
Which radiotracer is commonly used in salivary gland flow scintigraphy?
(1) 99mTc-sulfur colloid
(2) I-131
(3) 99mTc-pertechnetate
(4) 99mTc-methyl diphosphonate
(5) I-131
What is the purpose of administering a sialogogue such as citrate or lemon juice to the patient?
(1) To promote the migration of radiotracer into the salivary glands.
(2) To stimulate the release of trapped radiotracer and saliva from the salivary glands.
(3) None of the above.
What is a possible cause of the patient's parotid dysfunction?
(1) Previous I-131 ablation therapy
(2) Surgical complications from thyroidectomy
(3) All of the above
(4) None of the above

Additional Image

An axial T1-weighted MRI image of the parotid region of the face is provided.

Quiz 2

What is the most notable finding on MR imaging?
(1) Mildly atrophic but symmetric parotid glands
(2) Normal-appearing parotid glands
(3) Parotid gland hyperplasia with surrounding inflammatory changes

Findings and Diagnosis

Findings

Salivary gland scintigraphy: Significantly delayed uptake and trapping in both parotid glands. No appreciable excretion was observed from either parotid gland following stimulation with lemon juice. Both submandibular glands demonstrate symmetric and normal uptake, trapping, and excretion.
Facial T1-weighted MRI: Mild symmetric atrophy of the parotid glands.

Differential Diagnosis

Acute parotitis
Chronic parotitis
Sialadenosis
Parotid gland malignancy
Sjögren's syndrome
Sarcoidosis

Final Diagnosis: Chronic Parotitis

Discussion

Chronic Parotitis

Pathophysiology
Parotitis can present as acute (lasting less than a few weeks) or chronic (persisting for weeks to months).
Chronic parotitis may be caused by:

Malignancies of the parotid gland
Systemic inflammatory diseases such as Sjögren’s syndrome or sarcoidosis
Previous radiation exposure, including:
- I-131 therapy for thyroid malignancy
- External beam radiation therapy

Iodine-131 can accumulate in the salivary glands, where its beta emissions may cause cytotoxic damage. Approximately 25% of administered I-131 is excreted into saliva.
Acute sialadenitis from radiation typically results in ductal obstruction and salivary pooling, resolving within days.
In contrast, chronic radiation injury causes loss of fluid-producing acinar cells and inflammatory fibrosis of the ducts, often leading to chronic parotitis and xerostomia (dry mouth).

Epidemiology
High-dose radiation significantly increases the risk of persistent salivary dysfunction.

After a single 100–150 mCi dose of I-131, up to 34% of patients report persistent xerostomia at 5 months.
Long-term studies show 16.4% of patients continue to experience symptoms at 5 years.

Clinical Presentation

Parotid gland swelling and stiffness
Dry mouth
Foreign body sensation in the oral cavity
Local tenderness over the salivary glands

Imaging Features

Salivary scintigraphy may show:
- Markedly reduced uptake and trapping in affected glands
- Minimal or absent excretion after sialogogue stimulation (e.g., lemon juice or citrate)

Treatment

Conservative management is the first-line approach:
- Sour candies, lemon juice
- Saliva stimulants such as pilocarpine or cevimeline
Surgical options such as local gland excision or ductal dilation show mixed outcomes and are reserved for refractory cases.

Reference

(1) Clement SC, Peeters RP, Ronckers CM, et al. Intermediate and long-term adverse effects of radioiodine therapy for differentiated thyroid carcinoma–a systematic review. Cancer Treat Rev. 2015;41(10):925-934.

(2) Harbison JM, Liess BD, Templer JW, Zitsch RP 3rd, Wieberg JA. Chronic parotitis: A challenging disease entity. Ear Nose Throat J. 2011;90(3):E13-E16.

(3) Sunavala-Dossabhoy G. Radioactive iodine: An unappreciated threat to salivary gland function. Oral Dis. 2018;24(1-2):198-201.

(4) Tanwar KS, Rana N, Mittal BR, Bhattacharya A. Early quantification of salivary gland function after radioiodine therapy. Indian J Nucl Med. 2021;36(1):25-31.

(5) Upadhyaya A, Meng Z, Wang P, et al. Effects of first radioiodine ablation on the functions of salivary glands in patients with differentiated thyroid cancer. Medicine (Baltimore). 2017;96(25):e7164.

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