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Parotid Abscess

Summary

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  • Parotid abscess is a localised collection of pus within the parotid gland
  • Typically results from bacterial infection, often ascending from the oral cavity
  • Presents with painful swelling of the parotid region, fever, and trismus1

Pathophysiology

  • Caused by bacterial infection, most commonly:
    • Staphylococcus aureus
    • Streptococcus species
    • Anaerobic bacteria
  • Infection usually ascends from the oral cavity via Stensen's duct
  • Risk factors include:
    • Dehydration
    • Poor oral hygiene
    • Immunosuppression
    • Ductal obstruction (e.g., sialolithiasis)
  • Progression of acute suppurative parotitis if left untreated

Demographics

  • Can occur at any age, but more common in:
    • Elderly patients
    • Immunocompromised individuals
    • Patients with poor oral hygiene
  • No significant gender predilection
  • Incidence has decreased with improved dental care and antibiotic use

Diagnosis

  • Clinical presentation:
    • Acute onset of painful swelling in the parotid region
    • Fever and malaise
    • Trismus (difficulty opening mouth)
    • Purulent discharge from Stensen's duct
  • Laboratory findings:
    • Elevated white blood cell count
    • Increased C-reactive protein and erythrocyte sedimentation rate
  • Microbiological culture of pus or saliva to identify causative organism

Imaging

  • Ultrasound:
    • First-line imaging modality
    • Hypoechoic or anechoic area within the parotid gland
    • Internal echoes and septations may be present
    • Increased vascularity in surrounding tissues
  • CT with contrast:
    • Low-density fluid collection with rim enhancement
    • Surrounding inflammatory changes and oedema
    • Useful for assessing extent and potential complications
  • MRI:
    • Superior soft tissue contrast
    • T1-weighted: hypointense lesion
    • T2-weighted: hyperintense lesion with hypointense rim
    • Diffusion-weighted imaging: restricted diffusion within abscess

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  • 35-year-old male presented with a swelling over the left parotid gland.
  • MRI showed a peripherally enhancing collection causing diffusion restriction in the left parotid gland.

Treatment

  • Antibiotics with image-guided aspiration or surgical drainage; a rim-enhancing collection with central restricted diffusion distinguishes abscess from diffuse parotitis

Differential diagnosis

Differential Diagnosis Differentiating Feature
Acute parotitis (without abscess) Diffuse gland swelling without discrete fluid collection; no rim enhancement; no restricted diffusion
Parotid neoplasm Solid mass without fluid signal; no rim enhancement; no inflammatory fat stranding
Intraparotid lymphadenitis Discrete lymph nodes within parotid gland; no true glandular abscess cavity
Sialolithiasis Calculus visible in Stensen's duct on CT; may cause duct dilatation without abscess formation
Branchial cleft cyst (second) Well-circumscribed thin-walled cyst at angle of mandible or anterior to SCM; no restricted diffusion; no rim enhancement
Masseteric abscess Collection centred in masseter muscle rather than parotid gland parenchyma

  1. Lakshmi Narayana et al. Parotid abscess in children - A tertiary rural hospital experience. 2015. International journal of pediatric otorhinolaryngology - Open in new tab. ↩