Peritonsillar abscess (PTA) or quinsy is a potentially severe suppurative complication of upper respiratory infection that is frequently diagnosed and managed in the emergency department. The spectrum of disease (from early cellulitis to abscess) is thought to be due to the inflammation of the minor salivary glands (Weber’s glands) that lie superior to the palatine tonsils. Unfortunately, clinical signs, such as “hot potato” voice and soft palate deviation away from the affected side, classically used to diagnose PTA, are neither sensitive (78%) nor specific (50%) in differentiating simple pharyngitis from a drainable abscess. Given the morbidity associated with a missed PTA, some emergency physicians choose empiric drainage, leading to a high frequency of painful negative aspiration attempts.^1,2

Recently, point-of-care ultrasound has been shown to improve diagnostic accuracy in distinguishing between peritonsillar cellulitis from abscess, with sensitivities ranging from 89-95% and specificities ranging from 79-100%.3 Even though computed tomography scan has sensitivities near 100%, potentially harmful ionizing radiation, increased emergency department length of stay and health care costs all contribute to make point-of-care ultrasound ideal in the identification and management of suspected cases of PTA.

Anatomy

The palatine tonsils lie in the depression between the palatoglossal and palatopharyngeal arches, covered by a capsule formed by the intrapharyngeal aponeurosis (Pic. 1). The peritonsillar space is located between the palatine tonsils on the medial aspect and the fascia of the superior constrictor muscle on the lateral aspect. With cellulitis or abscess formation, infection can spread along this potential space, irritating surrounding muscles, and causing trismus.4 The carotid artery lies posterolateral to the peritonsillar space and can be identified readily with ultrasound when attempting to visualize the peritonsillar space.

Technique

Analgesia and Anesthesia

Intravenous analgesic and anti-inflammatory medicines should be administered to reduce the initial trismus that often prevents a thorough examination of the posterior pharynx (we recommend intravenous ketorolac 15-30 mg and dexamethasone 10 mg for adults). Topical anesthesia can be accomplished with nebulized lidocaine (5 mL 2% lidocaine) via a facemask and augmented by atomizing 2% lidocaine directly onto the posterior pharyngeal mucosa. Additionally injecting a small amount of submucosal anesthetic (1-2% lidocaine with epinephrine) with a small-gauge needle (25 to 30 g) in the area of concern can provide a high level of anesthesia and facilitate both the posterior pharynx examination and needle aspiration.