The images indicate a peritonsilar abscess in this patient. The patient underwent incision and drainage with full resolution.
Peritonsillar Abscess
Peritonsillar abscess (PTA) is the most common deep space infection of the head and neck. It is a progression from tonsilitis to cellulitlis to abscess. It is often confused with peritonsillar cellulitis as they appear similar clinically. Ultrasound can be used to determine between the two without subjecting patients to blind needle aspiration. Using ultrasound to differentiate the two diagnoses is highly sensitive (>90%) and specific (>80%). PTAs usually appear as a hypoechoic or complex cystic mass, suggesting a pus pocket. If a fluid pocket is not denoted, then peritonsillar cellulitis is confirmed and the patient may be started on antibiotics without needle aspiration.
To evaluate the patient for PTA using intraoral ultrasound, the patient is first anesthetized topically. The endocavitary probe is covered with a non-sterile probe cover after gel is applied to the tip. The patient is seated with their head resting against the back of the bed or ENT chair and the probe is inserted into the mouth and directed to the affected tonsillar pillar. The area can be imaged in the transverse or longitudinal plane, although transverse imaging is easiest and used most often. The affected area is scanned from top to bottom localizing the abscess. Ultrasound can also be used to guide the needle aspiration.