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.

Ultrasound Exam

Position the ultrasound system just behind and lateral to the patient to allow the operator a direct view of the screen while performing the examination. Advance a cleaned and covered high-frequency (8-5 MHz), intra-cavitary probe into the patient’s mouth with the indicator pointing to the patient’s right (Pic. 2).

Always examine the unaffected tonsil first by fanning in a cephalad-to-caudad direction. Visualize both the lateral and superior aspect of the unaffected tonsil to ensure that you are familiar with normal sonographic anatomy. The unaffected/normal tonsil should be oval, have a central hyperechoic hilum and a hypoechoic periphery (as compared to adjacent muscle tissue). A more experienced sonographer can employ color power Doppler or color Doppler to detect the classic central flow of lymphatic tissue. Recognizing the normal sonographic appearance of the unaffected tonsil is critical in differentiating a peritonsillar abscess from peritonsillar cellulitis⁵ (Pic. 3).

After clearly visualizing the normal tonsil, repeat the examination for the affected tonsil. Again, look closely for any hypoechoic areas adjacent to the tonsil (most commonly located either superiorly or laterally). Similar to abscesses seen under the skin surface, the sonographer should look for a discrete hypoechoic cavity with disorganized purulent material. Novice sonographers can easily mistake a cellulitic tonsil for an abscess, and a clearly defined hypoechoic/anechoic pocket of fluid should be identified (Pic. 4 and Pic. 5). Finally, identification of the carotid artery allows the clinician to assess the proximity of the vessel in relation to the abscess cavity (commonly 3-4 cm behind the posterior pharynx)^2–4 (Pic. 6).

Peritonsillar Drainage

Although real-time, ultrasound guidance for needle drainage of peritonsillar abscess has been described, we recommend a pre-procedural marking technique. Because of the limited space in the posterior pharynx, concurrent real-time ultrasound needle visualization and abscess drainage can be technically challenging. We use ultrasound to diagnose and locate the abscess cavity, then remove the ultrasound and perform the needle drainage.

After the patient is comfortable, and the abscess has been identified, use a Macintosh laryngoscope (size 3 or 4) to expose and illuminate the target peritonsillar aspiration site. We recommend placing a 3.5 inch 18-20 g spinal needle on a 10 ml syringe with the distal 2 cm of the needle cover cut to limit the risk of inadvertent carotid artery puncture. The length of the spinal needle allows for the operator’s hand to maneuver freely outside the mouth during aspiration (Pic. 7). With the patient’s head supported, the operator should aspirate as the needle tip enters the abscess cavity.

Summary

Point-of-care ultrasound is an ideal tool for differentiating between peritonsillar cellulitis and peritonsillar abscess in the emergency department. A defined analgesic/anti-inflammatory “cocktail” will facilitate patient comfort and a thorough examination of the posterior pharynx. Finally, a clear scanning protocol that includes identifying the unaffected tonsil prior to the evaluation of the affected peritonsillar space will improve accuracy.

Question: Is the submandibular approach for identification of a peritonsillar abscess useful in the emergency department? If so, how is it performed?

Answer: The transcutaneous submandibular approach to peritonsillar abscess identification is performed with a high frequency linear probe. Place the probe below the mandible, aiming cephalad towards the peritonsillar region. Similar to the intraoral approach, we recommend trying to identify the contralateral/unaffected palatine tonsil. The transcutaneous approach is useful in patients with severe trismus, who are unable to open the mouth to tolerate an intraoral probe.^4,6

Bibliography

1. Clin Otolaryngol 2012 Apr;37(2):136–145.
2. Acad Emerg Med 2005 Jan;12(1):85–88.
3. Acad Emerg Med 2012 Jun;19(6):626–631.
4. Braz J Otorhinolaryngol 2006 Jun;72(3):377–381.
5. AJR Am J Roentgenol 2005 May;184(5):1691–1699.
6. Am J Emerg Med 2013 Jan;31(1):267.e1–3.

Dr. Miss is an emergency ultrasound fellow and attending physician in the Department of Emergency Medicine at Alameda County Medical Center, Highland General Hospital, Oakland, Calif.; Dr. Herring is an emergency ultrasound fellow and attending physician in the Department of Emergency Medicine, Alameda County Medical Center, Highland General Hospital, Oakland, Calif.; Dr. Mantuani is an attending physician

in the Department of Emergency Medicine, Alameda County Medical Center, Highland General Hospital, Oakland, Calif.; and Dr. Nagdev is the director of emergency ultrasound, Department of Emergency Medicine, Alameda County Medical Center, Highland General Hospital, Oakland, Calif.