Peritonsillar abscess is the most common deep infection of the head and neck, with a U.S. incidence of approximately 30 per 100,000 per year (~45,000 cases/year). [1-2] It is a collection of pus between the tonsillar capsule and the superior pharyngeal constrictor muscle, typically unilateral, and most commonly affects young adults. [1][3] Diagnosis is primarily clinical, and the cornerstones of treatment are drainage, antibiotics, and supportive care. [1]
1. History
- Severe, progressive, unilateral sore throat — often out of proportion to exam findings
- Odynophagia and dysphagia (difficulty swallowing is a strong predictor; OR 18.4) [4]
- Trismus (difficulty opening the mouth) — highly predictive of abscess vs. cellulitis (OR 2.4) [5]
- "Hot potato" or muffled voice [1][6]
- Referred ipsilateral otalgia
- Fever, malaise, and general toxicity
- Preceding sore throat or tonsillitis episode (11–56% have prior oropharyngeal infections) [2]
- Duration of symptoms, prior antibiotic use, prior PTA episodes
- Ability to tolerate oral intake (critical for disposition)
2. Alarm Features
- Airway compromise: stridor, drooling, inability to manage secretions, respiratory distress
- Bilateral pharyngeal swelling or floor-of-mouth swelling (consider Ludwig's angina) [7]
- Neck swelling, induration, or crepitus (suggests deep space extension — parapharyngeal/retropharyngeal abscess, necrotizing fasciitis)
- Hoarseness (concern for deeper extension) [8]
- Rigors, sepsis, or toxic appearance
- Trismus so severe that oral exam is impossible
- Signs of Lemierre syndrome: high spiking fevers, rigors, neck pain along the SCM, septic emboli [6]
- Descending mediastinitis (chest pain, dyspnea) — the most frequently described complication with 10% overall mortality [9]
3. Medications
- Antibiotics (first-line):
- Penicillin (IV penicillin G or oral amoxicillin) remains the drug of choice, covering Group A Streptococcus and Fusobacterium necrophorum [10-11]
- Amoxicillin-clavulanate or ampicillin-sulbactam (IV) for broader anaerobic coverage [12-13]
- Clindamycin for penicillin-allergic patients (no significant difference in outcomes vs. penicillin, but more adverse effects) [10]
- Ceftriaxone + metronidazole is an alternative IV regimen
- Metronidazole addition to penicillin: a systematic review of 3 RCTs found no evidence of additional benefit and increased side effects [14]
- Corticosteroids: A single dose of dexamethasone 10 mg IV reduces pain at 24 hours (1.4 vs. 5.1 pain score, p = .009) and may improve temperature, but the effect is short-lived [15-16]
- Analgesics: NSAIDs, acetaminophen, viscous lidocaine gargle; opioids as needed
- Medications to avoid: Aspirin (bleeding risk during drainage)
4. Diet
- Soft or liquid diet as tolerated during acute phase
- Aggressive IV hydration if unable to tolerate oral intake
- Cool liquids may provide symptomatic relief
- Advance diet as swallowing improves post-drainage
- Avoid spicy, acidic, or rough-textured foods until resolution
5. Review of Systems
- HEENT: Sore throat (unilateral vs. bilateral), voice change, ear pain, neck swelling, drooling
- Respiratory: Dyspnea, stridor, cough (concern for aspiration or airway compromise)
- GI: Ability to swallow liquids/solids, dehydration symptoms
- Constitutional: Fever, chills, rigors, weight loss, night sweats
- MSK: Neck stiffness, torticollis (may indicate parapharyngeal extension)
- Neuro: Cranial nerve deficits (rare, suggests cavernous sinus involvement)
6. Collateral History and Family History
- History of recurrent tonsillitis or prior PTA episodes (recurrence rate 10–15%) [2]
- Prior tonsillectomy (PTA is rare but not impossible post-tonsillectomy)
- Immunocompromised state (HIV, diabetes, chemotherapy)
- Smoking history — associated with increased risk
- Family history of recurrent throat infections
- Recent dental procedures or dental infections (odontogenic source) [17]
7. Risk Factors
- Acute tonsillitis (strongest association; OR 6.71) [18]
- Chronic tonsillitis (OR 2.00) and acute pharyngitis (OR 1.74) [18]
- Age 15–30 years (peak incidence), though all ages affected [3]
- Male sex (males constitute ~70% of complicated cases) [9]
- Smoking
- Immunosuppression (diabetes, HIV)
- Poor dental hygiene
- Age >40 years associated with higher complication risk [9]
8. Differential Diagnosis
- Peritonsillar cellulitis/phlegmon — no drainable collection; may be a precursor to PTA
- Retropharyngeal abscess — posterior pharyngeal wall swelling, neck stiffness, dysphagia; more common in children
- Parapharyngeal abscess — lateral neck swelling, trismus, medial displacement of tonsil/lateral pharyngeal wall
- Epiglottitis — drooling, stridor, "tripod" positioning; direct visualization or lateral neck X-ray
- Infectious mononucleosis — bilateral tonsillar enlargement, splenomegaly, atypical lymphocytes
- Tonsillar/oropharyngeal malignancy — unilateral tonsillar enlargement, weight loss, lymphadenopathy; consider in older adults or non-resolving cases
- Ludwig's angina — bilateral submandibular/sublingual space infection, floor-of-mouth elevation [7]
- Lemierre syndrome — septic thrombophlebitis of internal jugular vein, high fevers, septic emboli [6]
- Dental abscess with referred pain
9. Past Medical History
- Prior PTA episodes (recurrence rate ~10% in the U.S.) [2]
- History of recurrent tonsillitis
- Prior tonsillectomy
- Immunocompromising conditions
- Bleeding disorders or anticoagulant use (relevant for drainage)
- Allergies to antibiotics (especially penicillin)
- Diabetes mellitus
10. Physical Exam
- Vital signs: Fever, tachycardia; assess for signs of sepsis
- Oropharynx: Unilateral palatal arch protrusion/bulge (OR 29.7 for abscess), erythema, tonsillar exudate, medialization of the affected tonsil [5]
- Uvula: Deviation to the contralateral side [3]
- Trismus: Limited mouth opening (may limit exam)
- Voice: "Hot potato" or muffled quality
- Neck: Jugulodigastric (anterior cervical) lymphadenopathy; assess for induration, fluctuance, or crepitus suggesting deep space extension
- Airway: Assess for stridor, drooling, respiratory distress
- Floor of mouth: Evaluate for elevation (Ludwig's angina)
11. Lab Studies
- Routine labs are not required for straightforward PTA — CRP and WBC are not reliable predictors of abscess vs. cellulitis [5]
- Consider in ill-appearing patients:
- CBC with differential
- CRP (useful for monitoring therapy, not diagnosis)
- BMP (assess dehydration, renal function)
- Blood cultures (if septic or concern for Lemierre syndrome)
- Monospot/heterophile antibody (if mononucleosis suspected)
- Abscess culture: Not routinely necessary; evidence does not suggest benefit in examining abscess contents for microorganisms in uncomplicated cases. Consider in immunocompromised patients or treatment failures [2][17]
12. Imaging
- Not required for classic clinical presentation — diagnosis is clinical [1][3]
- Point-of-care ultrasound (POCUS): First-line imaging when diagnosis is uncertain
- Intraoral approach: sensitivity 91%, specificity 75% [19]
- Transcervical approach: sensitivity 80%, specificity 81% [19]
- POCUS improves aspiration success (89% vs. 25% without), decreases ENT consultations, CT use, and return visits [20]
- Contrast-enhanced CT neck: Gold standard imaging when:
- Concern for deep space extension (parapharyngeal, retropharyngeal abscess)
- Drooling, hoarseness, or neck swelling suggesting deeper infection [8]
- Failed drainage or clinical deterioration
- 100% sensitivity for PTA [3]
- Predictors of successful drainage on CT: abscess size >2 cm, soft palate effacement, continuous ring enhancement [21]
- CT is unnecessary in clear-cut, uncomplicated PTA [22]
13. Special Tests
- Needle aspiration: Both diagnostic and therapeutic — aspiration of pus confirms the diagnosis [23]
- POCUS-guided aspiration: Significantly improves success rates [20]
- Centor/McIsaac score: Useful for initial pharyngitis evaluation but has low discriminatory performance for PTA (AUC 0.76) [4]
- Rapid strep test: To evaluate for concurrent GAS pharyngitis
- S100A8/A9 (calprotectin): Emerging biomarker to differentiate PTA from peritonsillar cellulitis (sensitivity 92%, specificity 93% in combination with clinical features), though not yet widely available [24]
14. ECG
- Not routinely indicated
- Consider if:
- Sepsis or hemodynamic instability (evaluate for sepsis-related arrhythmias)
- Concern for Lemierre syndrome with septic emboli
- Pre-procedural assessment if general anesthesia is planned for tonsillectomy
15. Assessment
PTA is a clinical diagnosis characterized by the triad of unilateral peritonsillar swelling, uvular deviation, and trismus. [3] The infection is polymicrobial, with Group A Streptococcus and Fusobacterium necrophorum as the predominant pathogens (with age-dependent variation: GAS predominates in children ≤11 years, F. necrophorum in adolescents/young adults). [11] Most cases are uncomplicated and manageable in the outpatient setting. [1] Complications, though uncommon, can be life-threatening: descending mediastinitis (most common serious complication), parapharyngeal/retropharyngeal abscess, necrotizing fasciitis, and Lemierre syndrome carry a combined mortality of ~10%. [9]
16. Treatment Plan
Initial stabilization
- Assess and secure airway if any concern for compromise
- IV access, fluid resuscitation if dehydrated
Drainage (mainstay of treatment)
- Needle aspiration: First-line in the ED; 94–96% acute resolution rate; less painful than I&D; can be performed with POCUS guidance [2-3][20]
- Incision and drainage (I&D): Higher first-attempt success (90% vs. 76%) and greater drainage volume, but more invasive; may have lower recurrence rate [3][25]
- Both methods are effective; no high-quality evidence favoring one definitively [3]
- Medical therapy alone (IV antibiotics + steroids without drainage): Emerging evidence suggests comparable failure rates (~5.7% vs. 5.5%), particularly in patients without trismus. However, this approach requires careful patient selection [26-28]
Antibiotics
- Penicillin (IV penicillin G → oral amoxicillin) is adequate empiric therapy [10-11]
- Ampicillin-sulbactam 3 g IV q6h or amoxicillin-clavulanate 875/125 mg PO BID for broader coverage
- Clindamycin 600–900 mg IV q8h (or 300 mg PO QID) for penicillin allergy
- Duration: typically 10–14 days total (IV → oral step-down)
Adjuncts
- Dexamethasone 10 mg IV × 1 dose — reduces pain at 24 hours [15]
- NSAIDs and acetaminophen for pain
- IV fluids for hydration
- Topical anesthetics (viscous lidocaine, benzocaine spray)
17. Disposition
Discharge criteria (most patients can be managed outpatient): [1]
- Successful drainage with clinical improvement
- Able to tolerate oral intake (fluids and medications)
- No signs of airway compromise or deep space infection
- Reliable follow-up available
- No significant comorbidities or immunosuppression
Admission criteria
- Inability to tolerate oral intake
- Signs of sepsis or toxic appearance
- Airway compromise or concern for impending obstruction
- Suspected deep space extension (parapharyngeal, retropharyngeal abscess)
- Failed outpatient drainage
- Immunocompromised patients
- Unreliable follow-up or social concerns
ENT consultation triggers
- Failed needle aspiration
- Suspected deep space infection
- Recurrent PTA (consider tonsillectomy)
- Pediatric patients (especially if uncooperative for bedside drainage)
- Concern for malignancy
Tonsillectomy indications
- Recurrent PTA (especially in ages 15–25, where 30-day recurrence is 15.5%) [29]
- Concurrent history of recurrent tonsillitis meeting tonsillectomy criteria [30]
- Failed drainage requiring OR intervention
- Ipsilateral recurrence rate after drainage alone is low (~2.8%), so routine tonsillectomy after a single PTA is not recommended [22]
18. Follow Up / Return Precautions
- Follow-up: 24–48 hours post-drainage for reassessment; ENT follow-up within 1–2 weeks
- Return immediately for:
- Worsening throat pain or swelling
- Inability to swallow liquids or medications
- Difficulty breathing, stridor, or drooling
- High fever unresponsive to antipyretics
- Neck swelling or stiffness
- Chest pain (concern for mediastinitis)
- Expected course: Significant improvement within 24–48 hours of drainage; complete resolution typically within 7–10 days
- Recurrence: Overall 10–15% recurrence rate; highest in ages 15–24 (26.6% total recurrence); discuss tonsillectomy referral for recurrent episodes [2][29]
- Patient counseling: Complete the full antibiotic course; smoking cessation; maintain hydration; soft diet until symptoms resolve
References
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4. Risk Factors for Peritonsillar Abscess in Streptococcus a-Negative Tonsillitis: A Case Control Study. — Helfenberger L, Fischer R, Giezendanner S, Zeller A. Swiss Medical Weekly. 2021.
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