Peritonsillar Abscess Workup

Updated: Jul 25, 2022
  • Author: Benoit J Gosselin, MD, FRCSC; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Laboratory Studies

Patients presenting with peritonsillar abscesses (PTAs) often are septic in appearance and may demonstrate varying degrees of dehydration due to abstention from oral intake. Assessment of these two entities should involve the collection of blood for a complete blood count, electrolyte level measurement, and blood cultures.

In patients presenting with tonsillitis and bilateral cervical lymphadenopathy, a monospot test (heterophile antibodies) should be considered. If the test results are positive, the patient requires careful evaluation of hepatosplenomegaly. Liver function tests should be considered in patients with hepatomegaly.

To facilitate the identification of infectious organisms, a throat swab and culture are to be considered. The results may help the clinician select the most appropriate antibiotic once the organism is identified, limiting the risk of antibiotic resistance.


Imaging Studies

Imaging may be particularly useful in cases where an attempt at incision and drainage (I&D) has failed or where worsening edema in a treated peritonsillar cellulitis is noted. In certain cases, the abscess may be within the tonsil itself or partially hidden (ie, inferior or posterior) by the tonsil.

Plain radiography

Lateral soft tissue views of the nasopharynx and oropharynx may help the clinician rule out a retropharyngeal abscess. In the anteroposterior view, the films reveal distortion of soft tissues but are not useful in localizing an abscess.

Computed tomography

In selected clinical settings and in very young patients, radiologic evaluation may be performed by means of computed tomography (CT) of the oral cavity and neck using intravenous (IV) contrast enhancement.

Common findings are the presence of a hypodense fluid collection in the apex of the affected tonsil, with peripheral rim enhancement. Other findings may include an asymmetric enlargement of the tonsils and surrounding fossa. Further delineation of cervical adenopathy is facilitated, as is the identification of a possible intranodal fluid collection, which indicates a cervical abscess and helps in the planning of surgical management.


Intraoral ultrasonography has been proposed as an imaging modality. [12] It is a simple, well-tolerated, noninvasive technique that can help distinguish between cellulitis and the presence of an abscess. Intraoral ultrasonography also allows the option of a more directed aspiration of the tonsillar fossa before definitive surgical drainage is attempted. One study has shown that this approach is also clinically useful in the evaluation of patients presenting in the emergency department.


Diagnostic Procedures

Needle aspiration of the abscess site (see the image below) may be performed just before the drainage procedure is attempted. It allows identification of the location of the abscess in the peritonsillar space.

Pus is aspirated from right peritonsillar abscess Pus is aspirated from right peritonsillar abscess through large-bore needle. Additional incision will be made to drain any other pus pockets.

The aspiration site is anesthetized by using lidocaine with epinephrine, and a large-bore (16- to 18-gauge) needle is mounted on a 10-mL syringe. Infiltration is the method of choice for administering local anesthesia for aspiration and incision of peritonsillar abscesses. The needle is passed through the anesthetized mucosa, where aspiration of the site is performed. Aspiration of purulent material is diagnostic, and the material may be sent for culture.