A 25-year-old male with recurrent strep throat presents to the ED with sore throat, difficulty swallowing, and feeling as though his voice has changed. His physical exam is significant for a left sided, bulging tonsil. He is currently managing his own secretions, and his respiratory status is stable. You are concerned that he has not been able to drink any fluids since the night prior. He appears well hydrated, but you question if this is simple tonsillar cellulitis or a peritonsillar abscess (PTA). You know that clinical diagnosis of PTA only has a reported sensitivity of 78% and a specificity of only 50% (Lyon et al, 2005) and want to do further diagnostic imaging. Should this patient go to CT, or could you find an answer faster at the bedside with much less radiation? Can you drain this in the emergency department or does he need to proceed to the OR with ENT? He has gotten viscous lidocaine and his pain improved. His rapid strep was positive. You wheel out your bedside ultrasound and perform an intraoral ultrasound.
Using the endocavitary probe, you perform the following US of the peritonsillar region:
What is the diagnosis?
Point of Care PTA Ultrasound:
There are two techniques for performing an ultrasound of the tonsils - transcutaneous and intraoral.
Transcutaneous Ultrasound: This technique is useful in children, especially if performing a needle aspiration of the abscess, as it is less invasive and leaves spaces for aspiration equipment in the oral cavity. Using the linear high frequency transducer, positioned under the mandible with your probe marker towards the patient’s earlobe on the same side, first identify the submandibular gland, and then the tonsil, immediately deep to the submandibular gland.
Intraoral Ultrasound: As used in the case, this technique utilizes an endocavitary transducer after numbing the area with topical anesthetic for patient comfort. The transducer is placed intraorally abutting the area of suspected abscess with the probe marker facing the ipsilateral ear.
The tonsil is identified by the irregular surface, representing tonsillar crypts. An isoechoic ring surrounding an anechoic region identifies an abscess with posterior enhancement. Abscesses will develop in between the medial aspect of the tonsil and superior constrictor muscles. Posterior and lateral to the tonsil is the important internal carotid artery, which can be seen with pulsatile flow on color Doppler. It is important to identify this structure prior to draining of the abscess. It will run anterior to the jugular vein within the carotid sheath.
Peritonsillar Abscess on Ultrasound:
Intraoral sensitivity ranges from 90-100%
Transcutaneous sensitivity ranges from 80-91%
Enlarged tonsils with:
Heterogenous, cystic, anechoic fluid
Well circumscribed with irregular margins
Usually along the posterolateral aspect of tonsil
Can save a patient from the radiation of a CT scan (where sensitivity is 100%, but specificity is 75%)
Back to our case:
Can you find an answer to your patient’s symptoms quickly, at the bedside?
Yes! You should think of ultrasound to help you diagnose a PTA, which in the published literature has a comparable sensitivity to CT (see above)
Do you need an ENT and to send this patient to the OR?
Case reports suggest that US assisted drainage can replace CT and operative drainage of abscesses (Todsen et al. 2018), but a true trial comparing the two modalities is yet to be completed
It never hurts to use your ultrasound to determine what you can see!
Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections." Pediatric Radiology 46.7 (2016): 1059-067.
Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department." Academic Emergency Medicine 12.1 (2005): 85-88.
McLario, David J., and John L. Kendall, eds. Case Studies in Pediatric Emergency and Critical Care Ultrasound. Cambridge: Cambridge UP, 2013. Print.
Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.” Am J Emerg Med (2015).
Todsen, Tobias, Stage, Mads G., Hahn, Christoffer H. “A Novel Technique for Intraoral Ultrasound-Guided Aspiration of Peritonsillar Abscess.” Diagnostics 8.3 (2018)