Key Facts

Peritonsillar abscess (quinsy) is a collection of pus in the peritonsillar space, forming between the tonsillar capsule and the pharyngeal constrictor muscle. It is the most common deep neck space infection and the most common complication of acute tonsillitis requiring hospital admission.

Epidemiology

• Incidence: approximately 30 per 100,000 per year
• Peak age: 20-40 years (less common in young children)
• Male = Female
• More common in smokers
• Seasonal: winter and spring (parallel to tonsillitis)

Aetiology

• Usually develops as a complication of acute bacterial tonsillitis
• Infection spreads through the tonsillar capsule to the peritonsillar space
• Polymicrobial in most cases: GAS, Fusobacterium necrophorum, Prevotella, Staphylococcus aureus
• Weber's glands (minor salivary glands in the supratonsillar fossa) may serve as the site of initial abscess formation
• Risk factors: recurrent tonsillitis, smoking, dental infections, immunocompromise

Pathophysiology

• Acute tonsillitis → peritonsillar cellulitis → peritonsillar abscess
• Pus collects in the potential space between tonsillar capsule and superior constrictor
• Abscess typically forms at the upper pole of the tonsil (supratonsillar)
• Expanding abscess pushes tonsil medially and inferiorly
• Uvula is deviated away from the affected side
• Trismus results from inflammation of pterygoid muscles
• Can extend to parapharyngeal space if untreated

Typical Presentation

• Severe unilateral sore throat (progressively worsening, often despite antibiotics for tonsillitis)
• Trismus (difficulty opening mouth) — pathognomonic
• Muffled, 'hot potato' voice
• Odynophagia (pain on swallowing, often cannot swallow saliva)
• Drooling
• Referred otalgia (ipsilateral ear pain)
• High fever, malaise

Examination Findings

• Unilateral peritonsillar swelling — soft palate/anterior pillar bulging
• Uvula deviation away from the affected side
• Tonsil displaced medially, inferiorly
• Trismus (often cannot fully examine oropharynx)
• Tender, enlarged ipsilateral cervical lymph nodes
• Foetor oris (halitosis)

Red Flags

• Stridor or respiratory distress (airway compromise)
• Bilateral peritonsillar swelling
• Neck swelling extending below mandible (parapharyngeal extension)
• Torticollis (parapharyngeal/retropharyngeal abscess)
• Sepsis features (high fever, tachycardia, hypotension)
• Failure to improve after drainage (recurrence, deeper space infection)

Bedside

• Clinical diagnosis is usually sufficient (experienced clinician)
• Assessment of trismus severity
• Assessment of airway
• Temperature and observations
• Hydration status

Bloods

• FBC (raised WCC, neutrophilia)
• CRP (markedly elevated)
• U&Es (dehydration assessment)
• Blood cultures if sepsis suspected

Microbiology

• Aspirate pus for MC&S (guides antibiotic adjustment)
• Throat swab

Imaging

• Not routinely required if diagnosis is clinically clear
• CT neck with IV contrast: if diagnostic doubt, suspected deep space extension (parapharyngeal/retropharyngeal), failure to improve post-drainage
  • Shows rim-enhancing collection in peritonsillar space
• Intraoral ultrasound: emerging tool to differentiate cellulitis from abscess at bedside

Special Tests

• Needle aspiration: is both diagnostic and therapeutic (purulent aspirate confirms abscess)
• If no pus aspirated: likely peritonsillar cellulitis (treat with IV antibiotics alone)

Non-pharmacological

• IV fluid resuscitation if dehydrated
• Nil by mouth if airway concern or surgical drainage planned
• Analgesia and antipyretics
• Head elevation

Pharmacological

• IV antibiotics:
  • IV co-amoxiclav 1.2g TDS (covers GAS, anaerobes)
  • OR IV ceftriaxone 2g OD + IV metronidazole 500mg TDS
  • If penicillin allergy: IV clindamycin 600mg QDS
  • Duration: IV until improving, then oral for total 7-10 days
• Analgesia: paracetamol 1g QDS, ibuprofen 400mg TDS
• Dexamethasone 8-10mg IV stat: may reduce pain, trismus, and speed recovery (evidence supportive but not universally adopted)
• Topical anaesthetic gargle: benzydamine (Difflam) spray

Surgical/Interventional

• Needle aspiration: first-line drainage technique
  • Performed under local anaesthetic (topical + infiltration)
  • Success rate 85-95% with single or repeated aspiration
  • Aspirate sent for MC&S
• Incision and drainage: if aspiration fails or abscess re-accumulates
  • Performed under local anaesthesia in most cases
  • Break down loculations with Hilton's method (sinus forceps)
• Quinsy tonsillectomy (tonsillectomy à chaud): performed at same time as drainage
  • Definitive treatment; lower recurrence rate
  • Considered if: recurrent quinsy, meets tonsillectomy criteria
• Interval tonsillectomy: elective tonsillectomy 6-8 weeks after drainage

Referral Criteria

• All suspected quinsy requires same-day ENT assessment
• Emergency: airway compromise, deep space extension, sepsis
• Post-discharge: ENT follow-up for consideration of interval tonsillectomy

• Excellent prognosis with prompt drainage and antibiotics
• >95% resolve completely after drainage
• Recurrence: 10-15% without tonsillectomy; <1% after tonsillectomy
• Complications (rare with prompt treatment): parapharyngeal abscess (<5%), airway obstruction, aspiration pneumonia, Lemierre syndrome, internal jugular vein thrombosis, mediastinitis, sepsis
• Lemierre syndrome (septic IJV thrombophlebitis): mortality 5-18% historically; requires prolonged IV antibiotics and anticoagulation consideration
• Most patients discharged within 24-48 hours of drainage

Peritonsillar Abscess Drainage Technique

Indications for CT Neck in Quinsy