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%, Blavias et al, had 100%!) 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 (we used a 4% lidocaine neb and hurricaine spray in this case). 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. The sonologist can also denote the size, depth and relation of the abscess to the vascular structures that lie adjacent. Furthermore, ultrasound can be used to guide the needle aspiration. Although a little cumbersome, real time ultrasound guidance ensures that the needle is in the correct location and not extending past to the vascular structures posterior.
Blaivas M, Theodoro D, Duggal S. Ultrasound-guided drainage of peritonsillar abscess by the emergency physician. Am J Emerg Med.2003;21:155-158.
Lyon M, Blaivas M.Intraoral ultrasound in the diagnosis and treatment of suspected peritonsillar abscess in the emergency department. Acad Emerg Med.2005;12:85-88.
