In a patient with quinsy (peritonsillar abscess) who has undergone drainage and intravenous antibiotics, what clinical findings indicate the need for a repeat contrast‑enhanced CT of the neck?

Indications for Repeat CT in Quinsy (Peritonsillar Abscess)

Repeat contrast-enhanced CT of the neck after drainage and IV antibiotics for quinsy is indicated when the patient fails to show clinical improvement within 48-72 hours, develops new or worsening symptoms suggesting deep space extension, or presents with signs of airway compromise or systemic toxicity.

Clinical Scenarios Requiring Repeat Imaging

Primary Indications for Repeat CT:

• Lack of clinical improvement by 48-72 hours post-drainage 1

  • Persistent or worsening fever
  • Continued severe odynophagia
  • No reduction in trismus
  • Persistent or increasing neck swelling

• Signs of deep space extension or complications:

  • New onset of respiratory distress or stridor (airway obstruction)
  • Development of septic appearance or hemodynamic instability
  • Progressive neck swelling beyond the peritonsillar region
  • New neurological findings (cranial nerve deficits suggesting skull base involvement)
  • Chest pain or dyspnea (concern for descending mediastinitis)

• Recurrent abscess formation 2

  • Return of symptoms after initial improvement
  • Re-accumulation of purulent material

Important Caveats About Initial CT Use

The evidence reveals significant controversy about routine CT use in quinsy. CT has a false-positive rate of approximately 20-30% for peritonsillar abscess 3, 4, meaning many patients undergo unnecessary drainage attempts. One study showed only 69.6% of CT-diagnosed abscesses actually yielded purulence on drainage 4. Additionally, CT usage correlates with increased ED return visits and recurrent PTA 2, though this may reflect higher patient acuity rather than CT causing harm.

When Repeat CT Is NOT Needed

• Clinical improvement within 48-72 hours with resolution of fever, improved oral intake, and decreasing pain 1, 5
• Successful drainage with purulence obtained and subsequent symptom improvement
• Stable clinical examination without signs of deep space involvement

Algorithmic Approach to Repeat Imaging Decision:

1. Assess at 48-72 hours post-treatment:

   • Improving? → Continue antibiotics, no repeat CT needed
   • Static or worsening? → Proceed to step 2

2. Evaluate for deep space involvement:

   • Isolated peritonsillar symptoms? → Consider bedside re-aspiration first
   • Signs of parapharyngeal/retropharyngeal extension, airway compromise, or systemic toxicity? → Obtain repeat contrast-enhanced CT immediately 6

3. If repeat CT obtained:

   • Residual/recurrent abscess? → Repeat drainage or consider quinsy tonsillectomy
   • Deep space extension? → Surgical drainage under general anesthesia
   • No abscess (cellulitis only)? → Continue IV antibiotics 3

Critical Pitfalls to Avoid

• Do not rely solely on CT for initial diagnosis when clinical examination is classic for quinsy—this leads to unnecessary imaging and false positives 4, 7
• Do not repeat CT for routine follow-up in clinically improving patients—this adds unnecessary radiation and cost 2
• Do not miss malignancy: In patients with atypical presentations or recurrent "abscesses," consider that cystic degeneration of metastatic lymph nodes can mimic abscess on CT 3—ensure tissue biopsy if drainage yields no purulence or if clinical course is atypical
• Retropharyngeal space has lowest CT accuracy (PPV only 50%) compared to other deep neck spaces 3—maintain high clinical suspicion even with negative imaging

Contrast Administration

Always use IV contrast unless contraindicated (renal insufficiency, contrast allergy) 6. Contrast is essential for distinguishing abscess from cellulitis and mapping lesion borders. Non-contrast CT has minimal utility in this setting.