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Summary Table

Feature	Detail
Risk Factors	Young adults (20-40 years), recurrent tonsillitis, smoking, poor dental hygiene, immunosuppression, prior peritonsillar abscess
Etiology	Polymicrobial infection (Group A Streptococcus most common, also Fusobacterium, Prevotella, Staphylococcus aureus); complication of acute tonsillitis spreading to the peritonsillar space
Patient Presentation	Severe unilateral sore throat, progressive odynophagia, "hot potato" (muffled) voice, trismus, drooling, referred otalgia
Classic Physical Exam	Unilateral peritonsillar swelling with contralateral deviation of the uvula, trismus (limited mouth opening), tonsillar erythema and exudate, cervical lymphadenopathy
Key Diagnostic Results	Clinical diagnosis in most cases; intraoral ultrasound or CT with contrast if unclear; needle aspiration confirms pus
Management	Needle aspiration or incision and drainage (I&D), IV antibiotics (ampicillin-sulbactam or clindamycin), analgesics, consider interval tonsillectomy for recurrence
Keywords	"Hot potato voice," "trismus," "uvular deviation," "unilateral throat swelling," "drooling," "unable to swallow"

1. Pathophysiology

Peritonsillar abscess develops as a complication of acute tonsillitis or pharyngitis that extends beyond the tonsillar capsule into the peritonsillar space, a potential space located between the tonsillar capsule and the superior pharyngeal constrictor muscle. The infection begins as a cellulitis (peritonsillar cellulitis or "phlegmon") and, if untreated, organizes into a walled-off collection of pus.

The most commonly implicated organism is Group A beta-hemolytic Streptococcus (GAS), but cultures frequently reveal polymicrobial flora, including anaerobes such as Fusobacterium necrophorum and Prevotella species. This polymicrobial nature is why broad-spectrum coverage is required for treatment.

The abscess typically forms at the superior pole of the tonsil, between the anterior and posterior tonsillar pillars. As the abscess expands, it pushes the tonsil medially and inferiorly, which causes the classic finding of contralateral uvular deviation. The inflammatory swelling involves the medial pterygoid muscle, which explains the hallmark sign of trismus (inability to fully open the mouth). This anatomic relationship is a tested concept: trismus is not caused by pain alone but by direct inflammatory involvement of the pterygoid musculature.

The patient develops a "hot potato" voice because the enlarged peritonsillar mass displaces the soft palate and narrows the oropharyngeal airway, altering resonance. Drooling occurs because the severe odynophagia prevents the patient from swallowing their own saliva. Referred otalgia is explained by shared sensory innervation via the glossopharyngeal nerve (CN IX), which supplies both the tonsillar region and the middle ear.

The feared complication is extension into the parapharyngeal or retropharyngeal space, which can lead to airway compromise, mediastinitis, or erosion into the carotid sheath (causing internal jugular vein thrombophlebitis, known as Lemierre syndrome, classically associated with Fusobacterium necrophorum).

2. Classification and Clinical Manifestation

Stage	Description	Clinical Features
Peritonsillar Cellulitis (Phlegmon)	Diffuse inflammation without organized abscess cavity	Unilateral throat pain, mild swelling, erythema, no fluctuance, trismus may be mild or absent
Peritonsillar Abscess	Walled-off pus collection in the peritonsillar space	Severe unilateral throat pain, prominent bulging with fluctuance, marked trismus, uvular deviation, "hot potato" voice, drooling
Complicated / Extended Abscess	Spread beyond peritonsillar space into parapharyngeal or retropharyngeal space	Neck swelling, torticollis, respiratory distress, sepsis, potential airway obstruction

Clinical Manifestation

Symptom	Clinical Significance
Trismus	Distinguishes peritonsillar abscess from simple tonsillitis; indicates pterygoid muscle involvement
Unilateral bulging	Key exam finding; abscess is almost always unilateral
Uvular deviation	Deviated away from the affected side due to mass effect
Hot potato voice	Muffled quality from oropharyngeal narrowing
Drooling / inability to swallow	Indicates severe odynophagia; raises concern for impending airway compromise
Referred otalgia	Via CN IX; does not indicate otitis media

3. Diagnostic Workup

Test	Role	Key Findings
Clinical examination	Best initial assessment	Unilateral peritonsillar bulging, uvular deviation, trismus, fluctuance
Needle aspiration	Diagnostic AND therapeutic (confirmatory)	Aspiration of purulent material confirms abscess vs. cellulitis
Intraoral/transcervical ultrasound	Point-of-care adjunct	Hypoechoic fluid collection in peritonsillar space; helps differentiate abscess from cellulitis
CT neck with IV contrast	Used when diagnosis is uncertain or complication suspected	Rim-enhancing hypodense collection in peritonsillar space; evaluates for parapharyngeal or retropharyngeal extension
Throat culture / rapid strep test	Identifies GAS	Positive for Group A Streptococcus in many cases
Blood cultures	Reserved for toxic-appearing or septic patients	May identify bacteremia

Peritonsillar abscess is primarily a clinical diagnosis. In a patient presenting with unilateral tonsillar bulging, uvular deviation, trismus, and a "hot potato" voice, the diagnosis is clear from examination alone. Needle aspiration serves a dual role: it confirms the presence of pus (distinguishing a true abscess from cellulitis) and provides initial drainage.

When the clinical picture is ambiguous, particularly when trismus limits adequate oral examination, CT of the neck with IV contrast is the imaging study of choice. It demonstrates a rim-enhancing hypodense collection in the peritonsillar space and is critical for evaluating whether the infection has spread into the parapharyngeal or retropharyngeal spaces.

Intraoral ultrasound has gained favor as a bedside tool in the emergency department because it can rapidly distinguish a drainable abscess from cellulitis without radiation. However, CT remains superior for assessing deep space involvement.

Routine laboratory studies (CBC, CRP) may show leukocytosis and elevated inflammatory markers but are noncontributory to the diagnosis. They are useful primarily for monitoring the septic or immunocompromised patient.

4. Management and Treatment

Intervention	Details
Needle aspiration	First-line drainage procedure; 18-gauge needle directed into the point of maximal fluctuance at the superior pole; can be repeated if needed
Incision and drainage (I&D)	If needle aspiration fails or abscess recurs; performed with a guarded scalpel to prevent deep vessel injury
IV Antibiotics	Ampicillin-sulbactam 3 g IV every 6 hours (covers GAS, anaerobes, and S. aureus); alternative: Clindamycin 600-900 mg IV every 8 hours (for penicillin-allergic patients)
Oral step-down antibiotics	Amoxicillin-clavulanate 875/125 mg PO twice daily for a total antibiotic course of 14 days; alternative: Clindamycin 300 mg PO every 6 hours
Analgesics	NSAIDs (ibuprofen), acetaminophen, topical anesthetics; consider IV dexamethasone 10 mg single dose to reduce edema and pain
IV Corticosteroids	Dexamethasone 10 mg IV single dose: reduces peritonsillar edema, improves oral intake, shortens recovery
IV Fluids	For dehydration secondary to poor oral intake
Tonsillectomy	Interval ("quinsy tonsillectomy") considered after 2 or more episodes; immediate tonsillectomy ("a chaud") rarely performed but may be considered if drainage fails

Acute stabilization begins with airway assessment. Although frank obstruction is uncommon, the possibility of airway compromise should be evaluated in every patient, particularly those with bilateral involvement, extensive swelling, or deep space extension.

The next best step after clinical diagnosis is needle aspiration. This is both diagnostic and therapeutic. The aspiration is performed at the superior pole of the tonsil (the most common abscess location), using an 18-gauge needle with a guard to limit depth of penetration and avoid injury to the internal carotid artery, which courses posterolateral to the tonsillar fossa. Aspiration of pus confirms the diagnosis and often provides immediate symptomatic relief.

If needle aspiration fails to yield pus or if symptoms recur after drainage, formal incision and drainage is the next step. Some practitioners proceed directly to I&D as the primary intervention.

Antibiotic therapy should provide coverage for GAS, oral anaerobes, and staphylococci. The first-line regimen is ampicillin-sulbactam 3 g IV every 6 hours. For penicillin allergy, clindamycin is the standard alternative and offers good anaerobic and gram-positive coverage. Once the patient can tolerate oral intake, antibiotics are transitioned to amoxicillin-clavulanate or oral clindamycin to complete a 14-day total course.

A single dose of IV dexamethasone is supported by evidence showing faster symptom resolution, reduced pain, and improved ability to resume oral intake. This is a commonly tested adjunct.

Interval tonsillectomy is recommended for patients with recurrent peritonsillar abscess (two or more episodes). Immediate (or "hot") tonsillectomy during the acute infection is less commonly performed but may be appropriate in select cases where drainage fails.

Contraindications and cautions: In patients with suspected extension into the parapharyngeal space or signs of Lemierre syndrome (spiking fevers, rigors, neck tenderness along the sternocleidomastoid, pulmonary infiltrates), CT imaging is mandatory and surgical consultation for operative drainage should not be delayed. Anticoagulation may be considered for Lemierre syndrome in addition to prolonged IV antibiotics.

5. Differential Diagnosis and Distractors

Differential Diagnosis	Why It Is Similar	Key Discriminator
Acute tonsillitis / Pharyngitis	Sore throat, fever, tonsillar exudate	Bilateral involvement, NO uvular deviation, NO trismus, NO unilateral bulging; responds to antibiotics alone
Retropharyngeal abscess	Sore throat, fever, neck stiffness, drooling; can be a complication of pharyngitis	Typically in children < 6 years; neck hyperextension, refusal to flex neck; CT shows posterior pharyngeal wall collection (prevertebral space widening on lateral X-ray)
Parapharyngeal abscess	Deep neck infection with trismus, fever, neck swelling	External neck swelling more prominent; medial bulging of lateral pharyngeal wall (not the tonsil itself); CT shows collection lateral to pharynx
Epiglottitis	Sore throat, drooling, muffled voice, airway concern	Rapid onset stridor, "thumbprint sign" on lateral neck X-ray, patient sits upright in "tripod" position; NO unilateral tonsillar bulging
Ludwig angina	Trismus, drooling, odynophagia	Bilateral submandibular space infection; floor of mouth elevation, tongue protrusion; recent dental infection history
Infectious mononucleosis with tonsillar hypertrophy	Severe bilateral tonsillar enlargement, exudate, sore throat	Bilateral and symmetric; posterior cervical lymphadenopathy, hepatosplenomegaly, atypical lymphocytes on smear; positive heterophile antibody test
Peritonsillar cellulitis (phlegmon)	Unilateral tonsillar erythema and swelling, odynophagia	No fluctuance, no discrete collection on imaging; needle aspiration is negative for pus; treated with antibiotics alone (no drainage needed)

6. Traps and High-Yield Pearls

The most common way students lose points on peritonsillar abscess questions is by confusing it with simple tonsillitis and selecting "antibiotics alone" as the answer. The test-writer includes trismus, uvular deviation, or a "hot potato" voice precisely to signal that the infection has progressed beyond the tonsil. When any of these findings are present, drainage is required in addition to antibiotics; antibiotics alone are insufficient.

A second trap involves differentiating peritonsillar abscess from retropharyngeal abscess. Both can present with drooling and a muffled voice. The key: retropharyngeal abscess occurs in young children and features neck rigidity with refusal to extend, whereas peritonsillar abscess occurs in young adults and features trismus with uvular deviation.

Students also sometimes confuse the voice change in quinsy with that of epiglottitis. In peritonsillar abscess, the voice is muffled ("hot potato") due to oropharyngeal narrowing, whereas epiglottitis produces stridor and a "toxic" appearance with rapid deterioration. The presence of unilateral pharyngeal bulging is the discriminating finding.

Finally, be aware of the Lemierre syndrome association. If a vignette describes a young patient with a recent sore throat followed by spiking fevers, rigors, and septic pulmonary emboli (multiple peripheral lung nodules on chest imaging), think Fusobacterium necrophorum and internal jugular vein thrombophlebitis. This is the feared complication of untreated or inadequately treated peritonsillar or pharyngeal infections.

The core competency being tested is the ability to recognize the clinical constellation that distinguishes a drainable abscess from uncomplicated pharyngitis and to understand that the next best step is drainage, not just escalation of antibiotics.

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