How is a peritonsillar abscess diagnosed?

Diagnosis of Peritonsillar Abscess

Primary Diagnostic Approach

Peritonsillar abscess should be diagnosed primarily through clinical examination, with imaging reserved for atypical presentations or when the diagnosis remains uncertain. 1, 2

Clinical Diagnosis

• Clinical examination is the first-line diagnostic method and includes assessment for fever, severe throat pain, dysphagia, trismus, and the characteristic "hot potato" voice 3, 2
• Physical examination should identify unilateral tonsillar swelling, uvular deviation away from the affected side, and soft palate bulging 2
• Digital examination of the peritonsillar area is essential to assess for fluctuance, which indicates abscess formation rather than cellulitis 1
• Clinical impression alone has limited accuracy (sensitivity 78%, specificity 50%), making confirmatory testing valuable in uncertain cases 4

When Imaging Is Indicated

Imaging should be obtained when:

• The clinical presentation is atypical or unclear 1
• Physical examination is limited by severe trismus or pain 1
• Complications such as deep neck space extension are suspected 2
• The patient fails to respond to initial drainage and antibiotics 2

Imaging Modality Selection

CT with Intravenous Contrast (Preferred Imaging)

• CT with IV contrast is the preferred imaging modality when radiologic confirmation is needed, as it visualizes fluid collections and demonstrates rim-enhancement of abscesses 1
• CT is less operator-dependent than ultrasound and maintains diagnostic accuracy even when severe pain limits physical examination 1
• Non-contrast CT has lower sensitivity and should be avoided 1

Intraoral Ultrasound (Alternative)

• Intraoral ultrasound can be useful for confirming diagnosis with high specificity (100%) and good sensitivity (89%) 4
• Ultrasound is more operator-dependent and has limited utility for deep-seated abscesses 1
• This modality may be helpful when available and expertise exists, particularly to distinguish abscess from cellulitis 5, 4

MRI (Not Routinely Used)

• MRI offers superior soft tissue resolution but is not typically used initially due to limited emergency availability and longer acquisition times 1
• MRI is more appropriate for complex cases, recurrent disease, or when detailed anatomical information is needed 1

Diagnostic Confirmation

Needle aspiration remains the gold standard for both diagnosis and treatment of peritonsillar abscess 3

• Aspiration provides definitive confirmation by obtaining purulent material 3
• This procedure is both diagnostic and therapeutic, making it the preferred approach when abscess is clinically suspected 3

Critical Pitfalls to Avoid

• Do not routinely order CT scans for straightforward clinical presentations, as CT usage is associated with increased ED return visits (OR 5.900), recurrent PTA (OR 1.943), and unnecessary medication prescriptions 6
• Avoid relying solely on clinical impression without confirmatory testing in uncertain cases, given the 50% specificity of clinical diagnosis alone 4
• Do not use non-contrast CT, which has significantly lower sensitivity compared to contrast-enhanced studies 1
• Imaging should not delay definitive treatment (drainage) when clinical diagnosis is clear and the patient requires urgent intervention 1, 2