About This Page
This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Peritonsillar abscess is the most common deep neck infection in adolescents and young adults
- Classic triad: severe unilateral sore throat, muffled hot-potato voice, and trismus with uvular deviation away from the affected side
- Management requires drainage plus antibiotics covering GAS, oral anaerobes, and Staphylococcus aureus
- CT neck with contrast is not always needed but is useful if diagnosis is uncertain, exam limited, or spread beyond peritonsillar space is suspected
- Drooling, stridor, toxic appearance, floor-of-mouth swelling, or inability to handle secretions = airway emergency
Overview
Peritonsillar abscess is a collection of pus in the peritonsillar space, usually a complication of acute tonsillitis or peritonsillar cellulitis. It is polymicrobial, commonly involving group A Streptococcus, Streptococcus anginosus group, Staphylococcus aureus, and oral anaerobes including Fusobacterium. The abscess pushes the tonsil medially and the uvula away from the affected side. Step 2 CK frequently tests the bedside recognition of unilateral tonsillar swelling plus trismus and the need for drainage rather than antibiotics alone.
Epidemiology
Peritonsillar abscess is most common in adolescents and young adults but can occur at any age. Risk factors include recurrent tonsillitis, smoking, periodontal disease, and prior peritonsillar abscess. It is less common in very young children but more dangerous when airway assessment is difficult. Recurrent abscess or recurrent severe tonsillitis may lead to consideration of tonsillectomy under AAO-HNS tonsillectomy guidance.
Clinical Features
Symptoms
Severe unilateral sore throat with odynophagia and referred otalgia
Muffled hot-potato voice
Trismus from pterygoid irritation
Fever, malaise, drooling, or inability to swallow saliva
Neck swelling, stiffness, toxic appearance, or respiratory distress suggests deep neck spread
Recurrent unilateral symptoms or persistent tonsillar asymmetry after infection resolves raises malignancy concern
Signs
Unilateral tonsillar bulge with soft palate edema
Uvula deviates away from affected side
Tender cervical lymphadenopathy
Limited mouth opening due to trismus may restrict examination
Stridor, tripod positioning, or inability to handle secretions is an airway emergency
Investigations
First-line
Clinical diagnosisClassic unilateral tonsillar swelling, uvular deviation, muffled voice, and trismus is usually sufficient
Needle aspirationDiagnostic and therapeutic; pus confirms abscess and can be sent for culture in severe/recurrent cases
Second-line
CT neck with IV contrastIf diagnosis uncertain, severe trismus prevents exam, concern for parapharyngeal/retropharyngeal extension, toxic appearance, or failed drainage
CBC and BMPIf systemically unwell, dehydrated, hospitalized, or needing IV therapy
Throat testingMay identify GAS but does not replace drainage when abscess is present
Specialist
ENT evaluationChildren, airway concern, failed aspiration, recurrent abscess, complicated deep neck infection, or need for operative drainage
Airway assessment/anesthesiaIf drooling, stridor, respiratory distress, or inability to lie flat
1
Stabilize and assess airway
- Evaluate ability to handle secretions, hydration status, respiratory distress, and deep neck spread
- Give IV fluids and analgesia/antipyretics as needed
- Airway compromise requires urgent ENT/anesthesia involvement before imaging delays
2
Drainage
- Needle aspiration, incision and drainage, or quinsy tonsillectomy depending on age, severity, local expertise, and recurrence
- Drainage is usually required for abscess; antibiotics alone may be insufficient except very small abscess or cellulitis under close follow-up
3
Antibiotics
- Oral options after drainage: amoxicillin-clavulanate or clindamycin
- IV options for severe disease: ampicillin-sulbactam or clindamycin; add MRSA coverage if risk factors
- Cover GAS and oral anaerobes; macrolide monotherapy is inadequate due to Fusobacterium resistance concerns
4
Adjuncts and follow-up
- Single-dose corticosteroid may reduce pain and speed oral intake in selected patients
- Observe until able to tolerate oral intake and no airway concern
- Consider tonsillectomy for recurrent tonsillitis or recurrent peritonsillar abscess according to ENT assessment
Complications
- Airway obstruction: Rare but life-threatening, especially with bilateral disease or severe edema
- Parapharyngeal/retropharyngeal spread: Neck stiffness, swelling, toxicity, mediastinal risk
- Lemierre syndrome: Fusobacterium necrophorum septic thrombophlebitis of internal jugular vein
- Aspiration: Rupture or drainage of abscess contents
- Recurrence: May require interval tonsillectomy
USMLE Step 2 CK Exam Tips
- 1Unilateral sore throat + trismus + uvula deviated away = peritonsillar abscess
- 2Next best step in classic stable PTA: needle aspiration or incision and drainage plus antibiotics
- 3Antibiotics must cover GAS and anaerobes; amoxicillin-clavulanate or clindamycin are common oral choices
- 4CT neck is for uncertain diagnosis or suspected deep neck spread, not every classic PTA
- 5Drooling/stridor/inability to handle secretions = secure airway before CT
- 6Hot-potato voice is a classic stem phrase
- 7Persistent unilateral tonsillar enlargement after infection = evaluate for malignancy
practicetest your knowledge on peritonsillar abscessApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — ent and beyond.
open q-bank