Sonographic evaluation of peri-tonsillar abscess Ayomide Loye PGY 1

PERItonsillar aBscess Most common deep space infection of head and neck Incidence of 1 in 10,000. Most common in adolescent with an antecedent sore throat Clinical presentation: ill appearance with fevers, dysphagia/odonophagia, trismus, drooling, peritonsillar erythema + swelling and muffled “hot potato” voice Complications Rupture into airway Dissection into carotid Regional spread leading to sepsis.

Anatomy of a Peri-tonsillar abscess Pathophysiology: Inflammation of minor salivary gland (Weber’s gland) which lies superior to the tonsils. Affected tonsil is anteriorly and medially displaced. Uvula displaced away from affected side. Carotid artery and jugular vein located 2.5cm posterior and lateral to tonsil Anatomy of a peritonsillar abscess. The palatine tonsil and peritonsillar space are identified on the patient’s left. A peritonsillar abscess (x) is shown on the patient’s right. Note that the abscess can extend medially, displacing the uvula. The carotid artery and jugular vein are posterior and lateral to the abscess Avoid lateral angulation of the aspirating needle and use a needle guard to prevent injury.

Landmark based pta Picture courtesy of Roberts and Hedges and Dr Ghorayeb at www.ghorayeb.com ICA located about 2.5cm posterior and lateral to tonsil so minimal room for error. if the aspirate is positive for pus, remove as much purulent material as possible. If the aspirate is negative, attempt aspiration again in the middle pole of the peritonsillar space, approximately 1cm caudal to the first aspiration. Perform a third and final attempt at the inferior pole. Up to 30% of abscesses will be missed if only the superior pole is aspirated. It must be stressed that a negative aspirate does NOT rule out a PTA 0.5-second spray of topical anesthetic (14% benzocaine, 2% Butamben, 2% tetracaine) to the posterior pharynx. Additional anesthesia was used by infiltrating 0.5 mL of 1% lidocaine to the posterior pharynx directly over the area to beaspirated.

Ultrasound Guided PTA Drainage Equipment Intraoral or Intracavitary probe. Procedure and Technique Cover intracavitary probe with a layer of gel and probe cover With patient sitting up, insert probe into mouth to side of suspected abscess (Might be helpful for patient to insert probe to prevent gagging and anxiety) Determine size and depth of fluid collection. Determine depth of carotid artery Chose appropriate needle length Complications Rare. Mostly due to sonographic image misinterpretation.

Collection of hypoechoic material surrounded by an echogenic capsule

Transverse plane of Left PTA with distance to front of abscess cavity and distance to carotid artery.

Prospective randomized controlled clinical trial Prospective randomized controlled clinical trial. Enrolled if they had constellation of signs and symptoms of PTA. Pts randomized to receive intraoral US or undergo LM drainage. US performed using 8 -5Mhz intracavitary transducer prior to procedure LM performed using visual landmarks in a superior to inferior approach until pus was obtained. Follow up in 2 days. 28 patients enrolled with 14 in each arm

Study Conclusion Ultrasound established correct diagnosis (PTA vs PTC) more than LM More successful aspiration of purulent material with US ENT consult rate was 7% for US vs 50% for LM CT usage rate was 0% for US vs 35% for LM Limitations: Convenience sampling Treating clinicians have more US knowledge and less experience with landmark based PTA drainage

ULTRASOUND VS CT SCAN Prospective single cohort study where 24 patients were evaluated in the ED for peritonsillar infection. Intraoral ultrasound was performed and presence or absence of abscess was noted. Conclusion: Ultrasound sensitive imaging modality and can be a strong initial imaging choice in patients with PTA Can rule out abscess and make CT unnecessary.

Ultrasound vs clinical diagnosis vs Ct Scott et al: Prospective study with sample size of 14 patients to determine diagnosis of peri-tonsilar infection using clinical diagnosis, ultrasound and CT. Clinical impression Sensitivity: 78% Specificity: 50% Ultrasound Sensitivity:89% Specificity:100% Computerized tomography Sensitivity:100% Specificity:75% Bottom Line: Intraoral US useful in improving accuracy in distinguishing abscess from cellulitis Sensitivity: probability that a test detects disease when disease is present Specificity: probability that a test indicates non-disease when disease is absent.

Conclusion Ultrasound can improve accuracy of diagnosing PTA when used in conjunction with clinical diagnosis Ultrasound reduces the number of unnecessary needle aspiration attempts in patients suspected of having PTA Ultrasound led to more successful aspirations of PTA Ultrasound can reliably rule out abscess making CT scan for diagnosis unnecessary

REFERENCES 1)  Constantino T, Satz W, Dehnkamp W, Goett H. Randomized trial comparing intraoral ultrasound to landmark-based needle aspiration in patients with suspected peritonsillar abscess. Academic Emerg Med. 2012; 6:626-631.  2) Scott P.M., Loftus W.K., Kew J. et al. Diagnosis of peritonsillar infections: a prospective study of ultrasound, computerized tomography and clinical diagnosis. J Laryngol Otol. 1999; 113:229–232. 3) Roberts J, Hedges J. Clinical Procedures in Emergency Medicine, 6th ed. Philadelphia, PA: Saunders, 2014; 1282 4) Nogan S, Jandall D, Cipolla M, Desilva B. The use of ultrasound imaging in evaluation of peritonsillar infection. Laryngoscope 2015 Nov; 125(11): 2604-7 5) Scott PM, Loftus WK, Kew J, Ahuja A, Yue V, van Hasselt CA. Diagnosis of peritonsillar infection: a prospective study of ultrasound, computer tomography and clinical diagnosis.