Transcervical Ultrasonography in the Diagnosis of Pediatric Peritonsillar Abscess

Samantha Huo, MD MPH, PGY-1 

The article: “Transcervical Ultrasonography in the Diagnosis of Pediatric Peritonsillar Abscess.” Fordham M. Taylor, et al. Laryngoscope, 125:2799–2804, 2015.

The idea: Peritonsillar abscess (PTA) is the most common deep neck infection, particularly in adolescents. Clinical examination alone is unreliable in distinguishing between an abscess and cellulitis, even when performed by ENTs. CT is the most sensitive imaging modality (100% sensitivity) for diagnosis of PTA, however, its use is limited by cost and radiation exposure (particularly in the pediatric population). US has been shown to be reliable in not only distinguishing abscess from cellulitis in the adult population, but also in guiding aspiration and drainage of PTA in adults (primarily using intra-oral ultrasound). This was the first study to address the use of US in diagnosing PTA in pediatrics. They used the transcervical approach (as opposed to intra-oral), which can be a good option for those patients who are unable to tolerate intra-oral US (due to pain, trismus, age, etc.).

The study: Prospective single-arm cohort study in a pediatric ED

  • Inclusion criteria: convenience sample of children and adolescents who were suspected to have a PTA based on history and physical exam

  • Exclusion criteria: <2 years old, significant airway compromise, suspected retropharyngeal processes

  • A pediatrics or PEM physician evaluated the patient and then consulted ENT for regular management of a suspected PTA based on clinical impression. All patients underwent transcervical US in addition (presumably performed by an US tech but the paper does not specify), and images were read by a blinded radiologist.

  • Clinical outcomes were reviewed retrospectively and compared to US findings.

The results:

  • n=43, ages 2-20

  • Transcervical US for diagnosing pediatric PTA has a:

    • Sensitivity of 100% (86.8%-100%)

    • Specificity of 76.5% (58.9%-89.2%)

    • PPV of 52.9% (27.9%-77.1%)

    • NPV of 100% (66.4%-100%)

  • ·      Specificity was likely under-estimated because a false-positive was considered any patient who was not found to have a PTA on I&D or who was managed successfully medically. It is possible that patients who were managed medically had pockets of purulence. 

The Take-Away: This study demonstrated that transcervical US, with a sensitivity of 100%, is a great rule-out test for PTA. Transcervical US is a relatively benign exam and is more tolerable than intra-oral ultrasound. The ultrasounds in this study were performed by US techs and read by radiologists, so we unfortunately don’t have any conclusions on the reliability of POCUS (performed and read by EM physicians) in diagnosing PTA. The authors of the study have since adopted a PTA algorithm at their institution that incorporates US (see figure below), and it will be interesting to see if they publish any further findings in the next few years.

PTA .png