What are the causes of sialadenitis?

Causes of Sialadenitis

Sialadenitis is primarily caused by bacterial infections (most commonly Staphylococcus aureus), viral infections (particularly mumps), and obstructive factors such as salivary stones, with other causes including post-surgical complications, immunocompromised states, and systemic diseases. 1, 2, 3

Infectious Causes

Bacterial Causes

• Staphylococcus aureus - most common bacterial pathogen 4
• Other aerobic and anaerobic bacteria 4
• Rare bacterial causes:
  • Actinomycosis
  • Tuberculosis
  • Atypical mycobacteriosis (may mimic salivary gland tumors) 4

Viral Causes

• Paramyxovirus (mumps) - most common viral cause globally 2, 5
• Juvenile recurrent parotitis - most common in vaccinated populations 5
• Human Immunodeficiency Virus (HIV) 3
• Respiratory syncytial virus - found in 20% of chronic sialadenitis cases 6

Obstructive Causes

• Sialolithiasis (salivary stones) - responsible for up to 50% of salivary gland disorders 5
  • More common in submandibular glands (>80% of cases) due to:
    • Long ducts flowing against gravity
    • Mucinous secretions high in calcium and phosphate salts 5
• Duct strictures 3
• Mucus plugs 5
• Post-surgical complications - particularly after skull base surgery 6
  • Mechanism: acalculous obstruction of submandibular duct due to prolonged rotation of head and neck
  • Can also involve ischemia and reperfusion injury 6

Predisposing Factors

• Dehydration - reduces salivary flow 4, 5
• Xerogenic medications (those causing dry mouth) 4
• Malnutrition 5
• Chronic illness 5
• Immunocompromised states 6:
  • Diabetes mellitus
  • Hematologic malignancies
  • Adrenal suppression
  • Chronic renal failure
  • Hematologic dyscrasia
• Granulomatous diseases 6:
  • Sarcoidosis (most common in US)
  • Wegener's granulomatosis
  • Infectious granulomatous diseases (rhinoscleroma, tuberculosis, leprosy, syphilis, fungal infections)

Anatomical Considerations

• Parotid glands - most susceptible to infections and neoplasms due to:
  • Largest of the major salivary glands
  • Produce aqueous serous secretions that are less immunogenic 5
• Submandibular glands - most susceptible to stone formation due to:
  • Mucinous secretions high in calcium and phosphate
  • Long ducts flowing against gravity 5

Special Considerations

• Invasive fungal sialadenitis - potentially fatal condition seen in immunocompromised patients
  • Caused by phycomycetes (Absidia, Mucor, Rhizopus species) or Aspergillus
  • Can rapidly progress from sinuses to central nervous system 6
• Post-surgical sialadenitis - rare complication (<1% of skull base surgeries)
  • Can lead to airway obstruction and neurological complications
  • Typically presents as submandibular swelling contralateral to craniotomy site 6

Clinical Pearls and Pitfalls

• The parotid gland is most commonly affected in bacterial sialadenitis 4
• Submandibular glands are responsible for more than 80% of salivary stones due to their anatomical and secretory characteristics 5
• Always consider potential airway compromise in severe sialadenitis cases, particularly post-surgical cases 6, 1
• Unusual neurological deficits (brachial plexopathy, facial nerve palsy, Horner syndrome) may occur with severe sialadenitis due to compression of neural elements 6
• Juvenile angiofibroma presenting with sialadenitis should not be biopsied due to risk of significant hemorrhage 6

Understanding these diverse causes helps guide appropriate management strategies, which range from conservative measures to surgical interventions depending on the specific etiology.