QA of the Month: May 2014
Congratulations to Dr. Cullnan and Dr. Schutz!
39 yo M, previously healthy, with 6 days of worsening throat pain. Recently with difficulty swallowing and opening his mouth. He had fevers, saw his PCP, who had prescribed azithromycin. The patient is afebrile in the ED, with normal vital signs. He has swelling to the right tonsillar pillar with mild uvula deviation. He is also noted to have mild trismus. No stridor, drooling, or difficulty breathing.
Ultrasound was performed of the RIGHT tonsillar fossa using the hockey stick probe:
An EBM approach: How good are we at clinical diagnosis of PTA?
In one study, otolaryngologists were able to clinically diagnose peritonsillar abscess versus peritonsillar cellulitis with 78% sensitivity and 50% specificity when compared to contrast CT and/or ultrasound.1 Traditional management has been to perform diagnostic (and potentially therapeutic) blind needle aspiration. Yet, blind needle aspiration carries a false-negative rate of 10-24%.2 A recent review highlights that intraoral ultrasound consistently has superior diagnostic and procedural advantages when compared to clinical exam alone.3 Intraoral sonography carries a 90-100% sensitivity allowing providers to differentiate between peritonsillar abscess and cellulitis. A number of case series and reviews now support the ability of EM physicians to accurately diagnose PTA.2,3-6 Further, a recent randomized trial compared POC ultrasound and landmark-based (i.e. blind aspiration) head-to-head amongst emergency department patients. Twenty-eight patients were enrolled with the findings that ultrasound doubled the success of emergency provider (EP) drainage from 50% to 100%, plummeted the ENT consult rate from 50% to 7%, and obviated CT usage from 35% to zero.5 Further, the number of needle pokes jumped from 1.4 to 2.4 between the US and Landmark groups presumably from the 33% EP failure rate of blind aspiration.
So how do I perform the exam?
As with any other skin/soft tissue exam, we are interested in superficial structures. Accordingly, a high frequency probe is best suited for this application.
5-10 MHz endocavitary probe (found in the Endocavitary box & requires cleaning by central supply)
5-10MHz ‘hockey-stick’ linear probe (found on the Peds US machine)
The ‘arm’ of the hockey-stick probe can be used to laterally retract the buccal mucosa, giving more exposure to the posterior oropharynx. Presence of severe trismus can be a limiting factor. A short 0.5-1 second burst of cetacaine spray (Beware methemoglobinemia), and/or other topical anesthetic will help with anesthesia. No gel is needed on the outer portion as wet mucosa is a great medium for ultrasound. Asking the patient to assist in holding and placing the probe can help with preventing the gag reflex.
Identify the carotid artery, and it’s relationship to the abscess (an anechoic or hypoechoic area that is absent from the unaffected side). Generally, the carotid will be posterolateral to the tonsil, within 5-25mm of the tonsil. Once you have your bearings, fan up and down to survey the whole region. Next, rotate the probe 90 degrees and evaluate the area in the longitudinal plane. A normal tonsil will be a small 10-20mm ovoid structure with a homogenous low-level echo texture. Enlarged tonsils with a homogenous or striated appearance would be considered peritonsillar cellulitis, whereas abscess will typically appear as a cystic, heterogeneous area with a poorly defined border7 (see QA image of the month). Once an abscess is identified, drainage may be performed dynamically or statically. Under real-time ultrasound guidance, the needle may be advanced. Alternatively, the probe can be removed from the patient’s oropharynx to allow an unobstructed view once spatial relationships have been sonographically explored and defined by the provider.
For more tips and tricks on the procedure itself:
The patient was consented for needle aspiration. He was prepped with Cetacaine Spray followed by local infiltration of lidocaine with epinephrine. With aspiration, 11cc of pus was obtained!!! The patient received steroids and antibiotics in the ED, felt much better, and was discharged on a course of appropriate antibiotics.
Congrats to Dr. Cullnan and Dr. Schutz on saving their patient from CT/radiation and a potential lengthy stay by having ultrasound-assisted diagnostic and procedural confidence.
- Josh Ennis, Mansour Jammal, and Laleh Gharahbagian
- Blokmanis A. Ultrasound in the diagnosis and management of peritonsillar abscesses. J Otolaryngol. 1994 Aug;23(4):260-2.
- Lyon M, Blaivas M. Intraoral ultrasound in the diagnosis and treatment of suspected peritonsillar abscess in the emergency department. Acad Emerg Med. 2005 Jan;12(1):85-8.
- Powell J, Wilson JA. An evidence-based review of peritonsillar abscess. Clinical Otolaryngol. 2012 Feb;37:136-45.
- Blaivas M, Theodoro D, Duggal S. Ultrasound-guided drainage of peritonsillar abscess by the emergency physician. Am J Emerg Med. 2003 Mar;21(2):155-8.
- Costantino TG, Satz WA, Dehnkamp W et al. Randomized Trial Comparing Intraoral Ultrasound to Landmark-based Needle Aspiration in Patients with Suspected Peritonsillar Abscess. Acad Emerg Med. 2012 June;19(6):626-31.
- Ramirez-Schrempp D, Dorfman DH, Baker WE et al. Ultrasound Soft Tissue Applications in the Pediatric Emergency Department: To drain or not to drain? Ped Emerg Care. 2009 Jan;25(1):44-8.
- Buckley A, Moss E, Blokmanis A. Diagnosis of peritonsillar abscess: value of intraoral sonography. Amer Jour Rad. 1994;162:961–4.