1. Sonographic evaluation of peri-tonsillar abscess
Ayomide Loye
PGY 1

2. 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.

3. 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.

4. Landmark based pta
Picture courtesy of Roberts and Hedges and Dr Ghorayeb at
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.

5. 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.

6. Collection of hypoechoic material surrounded by an echogenic capsule

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

8. 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

9. 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

10. 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.

11. 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.

12. 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

14. 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:  
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 ; 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):
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.