Peritonsillar Abscess

A peritonsillar abscess (PTA), also called quinsy, is a collection of pus between the capsule of the palatine tonsil and the pharyngeal muscles. A PTA is usually a complication of acute tonsillitis, an infection caused by group A Streptococci. Patients often present with a sore throat, trismus, and a muffled voice. The infection responds well to drainage and antibiotics. Complications such as the extension of infection to deeper spaces are possible.

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Epidemiology and Etiology


  • Most common deep neck infection in children and adolescents
  • Mostly seen in ages 15–30
  • Incidence is 30:100,000 people.


  • Group A Streptococcus (GAS), S. aureus, H. influenzae, anaerobic bacteria
  • Infection from acute tonsillitis penetrates the tonsillar capsule involving the surrounding tissues, causing peritonsillar cellulitis:
    • Eventually evolves into a peritonsillar abscess (PTA)
    • The abscess is located between the capsule of the palatine tonsils and the constrictor muscles of the pharynx.

Clinical Presentation

  • Systemic symptoms: fever, dehydration, malaise
  • Local symptoms: 
    • Sore throat, dysphagia, odynophagia, drooling
    • Extensive swelling in the tonsillar bed
    • Edema and medial deviation of the soft palate
    • Unilateral cervical lymphadenitis
  • Classic triad of symptoms:
    • Trismus: reflex spasm of the medial pterygoid, the most reliable indicator of a PTA
    • Uvular deviation: due to edema and medial deviation of the soft palate and peritonsillar fold
    • Dysphonia (“hot potato” voice): due to vagus nerve involvement causing failure to elevate the palate

Diagnosis and Management


  • Diagnosis is primarily clinical: by visualization of medial displacement of the tonsil and deviation of the uvula.
  • Confirmed by a collection of pus at the time of drainage
  • Gram stain and culture of aspirated fluid and throat culture aids in identifying causative pathogens for targeted antibiotic therapy.
  • If the spread of infection into deeper planes is suspected, a computed tomography (CT) scan should be performed.


  • For a patient presenting with impending airway obstruction, the 1st step in management is to secure the airway by intubation.
  • Drainage: 
    • Needle aspiration or incision and drainage
    • Surgical drainage may be required if purulent material cannot be removed with aspiration alone.
  • Antimicrobial therapy: 
    • Amoxicillin/clavulanate 
    • Clindamycin
  • Tonsillectomy may be considered for recurrent PTA.
Peritonsilar abscess

Computed tomography scan showing a left peritonsillar abscess and endotracheal tube preventing total airway occlusion

Image: “Peritonsillar abscess requiring intensive care unit admission caused by group C and G Streptococcus: a case report” by Gupta, N., Lovvorn, J., Centor, R.M. License: CC BY 3.0.


The spread of the infection into other parts of the body can lead to serious complications. These include the following:

  • Pneumonia: an infection of the lung parenchyma that can be caused by aspiration of bacteria into the lungs in the setting of a PTA or pharyngitis
  • Airway obstruction: a partial or complete blockage of respiration in the airways due to extensive edema from a PTA 
  • Retropharyngeal abscess: extension of a PTA into the retropharyngeal, deep neck, and posterior mediastinal space 
  • Sepsis: Fever, tachycardia, tachypnea, hypotension, and/or altered mentation leading to systemic organ dysfunction can be a result of bacteria entering the bloodstream from a previously localized infection.

Differential Diagnosis

  • Epiglottitis: an inflammation of the epiglottis most commonly caused by infection with H. influenzae. Epiglottitis presents with a “cherry-red” epiglottis, fever, dysphagia, drooling, and difficulty breathing. Epiglottitis is commonly seen in unvaccinated children. Treatment is with antibiotics and steroids. Although both epiglottitis and PTA show trismus on examination, findings of peritonsillar swelling and uvula deviation can help differentiate. 
  • Retropharyngeal abscess: abscesses that occur in the retropharyngeal space. Retropharyngeal abscesses can be caused by extension of local infections, such as upper respiratory infections, or from trauma such as dental procedures. Key clinical features include trismus, dysphagia, and the inability to extend the neck. Diagnosis is confirmed by CT of the neck. Management is primarily through antibiotics and surgical drainage. Complications include airway compromise, mediastinitis, and internal jugular vein thrombosis. The lack of peritonsillar findings helps differentiate a retropharyngeal abscess from a PTA.
  • Parapharyngeal abscess: an abscess, most often caused by dental infections, that extends into the lateral or posterior pharyngeal space. A parapharyngeal abscess presents with a fever, sore throat, and odynophagia. Treatment is with antibiotics and surgical drainage. Differentiated on examination, bulging is behind the posterior tonsillar pillar, not superior to it, while the soft palate and tonsils are normal.


  1. Galioto, N. J. (2017). Peritonsillar Abscess. American Family Physician, 95(8), 501–506. 
  2. Klug, T. E. (2017). Peritonsillar abscess: Clinical aspects of microbiology, risk factors, and the association with parapharyngeal abscess. Danish Medical Journal, 64(3), B5333. 
  3. Chang, B. A., Thamboo, A., Burton, M. J., Diamond, C., & Nunez, D. A. (2016). Needle aspiration versus incision and drainage for the treatment of peritonsillar abscess. The Cochrane Database of Systematic Reviews, 12(12), CD006287.
  4. Ellen R. Wald, M.D. (2019). Peritonsillar cellulitis and abscess. UpToDate. Retrieved November 17, 2020, from  

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