POCUS for Peritonsillar Abscess

Alexander Vanfleet, Allyson Hansen

TLDR

1.     Peritonsillar abscess (PTA) is the most common deep head/neck space infection presenting to the Emergency Department, with an incidence of approximately 1 in 10,000 patients.

2.     Use of Ultrasound is on the rise for PTA (25% in 2007-2008, 78% in 2013-2014) with associated improvement of Emergency physician success and decrease in ENT consults, CT usage, return visits, and LOS.

3.     We reviewed our case, including our “I&D Preparation” with a step-by-step breakdown of how to efficiently use Ultrasound to find a possible PTA, including locating the all important carotid artery.

4.     Further great resources including articles and videos on this topic can be found at bottom of the blog post!

Clinical Background

Peritonsillar abscesses (PTA) are localized collections of pus in the peritonsillar space between the tonsillar capsule and superior constrictor muscle. Due to this space being loose connective tissue, it is prone to abscess formation which can lead to a wide variety of clinical presentations - from a unilateral pharyngeal bulge to even sepsis.

Abscess formation typically occurs after tonsillitis and can also occur after mononucleosis. Some risk factors to keep in mind are smoking and chronic periodontal disease. It is the most common deep head/neck space infection presenting to the Emergency Department, with an incidence of approximately 1 in 10,000 patients. In the United States, the incidence is 30 per 100,000 among patients aged 5-59 years of age [1].

There is significant clinical overlap between peritonsillar cellulitis and abscess. Therefore, POCUS has developed into a helpful imaging modality for emergency physicians to differentiate between pathology as well aid in successful bedside aspiration which we will explore below.

How Does Ultrasound Help?

Different radiologic modalities can be considered to investigate for peritonsillar abscess including XR, contrast-enhanced CT imaging and intraoral ultrasonography. The sensitivity of ultrasound for the diagnosis of peritonsillar abscess is found to be 89-100% [2] which is similar to CT but without the radiation. Multiple studies have supported the use of ultrasonography in PTA.

In 2012, Costantino et al [3] published a prospective randomized study of adult patients that presented to a single emergency department with clinical suspicion for PTA. Subjects were randomized to US vs. landmark based aspiration for diagnosis. Intraoral US was performed by EM residents with attending oversight. There was a total of 28 patients enrolled. This study blended the question of diagnostic and therapeutic benefits of POCUS for PTA versus landmark based drainage. Ultrasound led to more accurate diagnostics and successful aspiration by the emergency doctors among other positive findings. Results are shown below in Table 1.

  Table 1. Outcomes of Costantino et al. Randomized Trial Comparing Intraoral Ultrasound to Landmark-based Needle Aspiration in Patients with Suspected Peritonsillar Abscess

In 2015, Secko and Sivitz [4] performed a brief literature review and cited a sensitivity of 89% to 95% and a specificity of 78% to 100% in diagnosing PTA when using intraoral ultrasound, depending on the sonographers expertise. Thus showing ultrasound can enhance diagnostic accuracy and reduce the risk of unnecessary surgical drainage.

After the 2012 Costantino study was performed, Gibbons et al. sought to investigate whether the behaviors of emergency physicians (EP) for the diagnosis and treatment of PTA had changed. Secondary outcomes were successful aspiration, frequency of specialty consultation, need for advanced imaging, unscheduled return visits within 1 week, and length of stay (LOS). This study showed that EP have changed how they diagnose this pathology. Prior to 2012 study by Constantino et al. 25% had utilized this modality which increased to 78% in 2013-2014. Secondary outcomes including EP success, ENT consults, CT usage as well as return visits and LOS were noted to have improved with POCUS. Ultrasound Gel created a great summary of this study depicted in Table 2.  Please peek at the Ultrasound Gel website and podcast for further details. Links below.

Table 2. Results of Gibbons et al. study summarized by: https://www.ultrasoundgel.org/posts/X_iZeT5q6pSW2I8xLfbDZQ

Case Presentation

A recent case we encountered was a 39 year old male who presented to our Emergency Department with two days of a worsening sore throat and episodic fevers. Pain gradually worsened to where he began experiencing right anterior neck discomfort, increased pain with swallowing, increased saliva and slight hoarseness in his voice.

Notable initial vitals found the patient to be afebrile 98.1 degree F, although heart rate was elevated to 117bpm. Exam showed mildly edematous midline uvula. No obvious tonsillar abscess or exudate visible although notable posterior pharyngeal erythema as well as anterior neck tenderness just inferior to the mandible with no obvious enlarged anterior lymph nodes or neck asymmetry or rigidity.  

Significant labs: WBC 19.94, Hemoglobin 16.4.

Initial imaging ordered at triage: CT soft tissue neck with contrast revealed a right peritonsillar well-circumscribed peripheral enhancing fluid collection measuring 10 x 8 x 22mm with mild surrounding edema.

Decision was made to attempt PTA drainage at the bedside via intracavitary US assistance.

Ultrasound Findings 

Image 1. With the above intracavitary US transverse view, we were able to accurately measure the dimensions of the PTA which measured 1.36 x 1.38 cm. Our third measurement observed the depth necessary for needle drainage and insertion into the abscess ~0.63mm. Lastly using color doppler, we appreciated the carotid artery which lies posterior and lateral to the tonsil, which was approximately 1.69cm in depth.

Image 2. This image shows a brief video clip of the carotid artery, which was confirmed by using color doppler while in transverse view.

Image 3. For educational purposes, this is another patient’s tonsil found using intraoral US. This transverse plane image helped identify abscess versus cellulitis in a patient without CT neck performed. We see a tonsil with hyperemia which commonly can be seen in patient with tonsillitis. While enlarged, there was no sizable abscess appreciated on exam or by ultrasound to further pursue I&D.

I&D Preparation

1.     To evaluate the PTA bedside, apply a sterile probe cover to an intracavitary probe.

2.     Have your patient sitting forward in a comfortable position holding suction in one hand to use as needed for saliva.

3.     Carefully place the US Probe toward to the posterior pharynx at area of PTA.

•   Initially the probe was held by the provider in a transverse manner, although patients may experience more comfort and may enhance imaging by holding the probe themselves with guidance by the provider.

•   If difficulty tolerating, topical anesthetic spray which is used for the I&D can be applied for imaging as well. Imaging from our patient is shown above in Images 1,2.

4.     After locating and measuring the abscess, topical anesthetic (benzocaine) was applied to site.

5.     Use an 18 gauge needle with 10cc syringe for the I&D.

6.     Prior to drainage, approximately ~0.6mm was measured and then cut off of the 18 gauge needle cap and then the cap was placed back onto the needle.

•   This provided a stopping point to prevent the needle from being inserted too deep - avoiding the ~1.69cm depth where we found the carotid. (Note:  ensure there are no sharp edges to the hard plastic cap after cutting).

7.     Secondary to mild trismus, we decided to perform via static approach by identifying abscess with POCUS and then aspirating without US guidance.

8.     At the most fluctuant area, insert the needle while aspirating.

In our case, we were able to aspirate a small amount of blood tinged, purulent fluid. To further assist during the I&D, the patient held a sterile speculum handle with a light depressing their tongue to help keep their mouth open and to provide comfort. Considering the speculum had a light, the posterior pharynx remained well lit and easily visible throughout the I&D.

Image 4. For further orientation, here is an anatomic illustration by AAFP showing landmarks. It is vital to keep in mind the carotid artery lies posterior and lateral to the tonsil as a major complication/risk is injury to the carotid artery during this procedure. For this reason, insertion should be 8mm or less. (Image and information provided by AAFP [4]).

Case Resolution

Using our ultrasound guided I&D we were able to provide some relief at the site although we continued with mainstay therapies. When considering antibiotic coverage for PTA, antibiotic choices should be effective against streptococcus and oral anaerobes as PTA are polymicrobial mixture of aerobic and anaerobic bacteria. Antibiotic therapy should be provided for 10 to 14 days. An American Family Physician (AAFP) article by Galioto provided a great, detailed chart of typical antibiotic therapies. The citation and link to article can be found under references, with the antibiotic recommendations being found in Table 5.

Additionally corticosteroid therapy may provide relief for edema, inflammation and help trismus. Corticosteroid therapy typically consists of dexamethasone 10mg or methylprednisolone 2-3mg per kg also cited in the Galioto article. It is important to stress antibiotic completion and appropriate follow-up to avoid further complications with regards to PTA including airway obstruction, aspiration, or worsening infection possibly into neck deep space.

Summary

In the ED setting, POCUS remains an essential tool as well as excellent assistant for procedural guidance as dynamic (real-time) imaging allows the operator to appreciate landmarks. Our blog post reviews its importance as an adjunct for patients with peritonsillar abscesses, which are the most common deep head/neck space infection presenting to the Emergency Department. The use of POCUS has been increasing over the years from 25% in 2007-2008 to 78% in 2013-2014. With this rise, improvement of secondary outcomes including EP success, ENT consults, CT usage as well as return visits and LOS have also been appreciated. We reviewed the stepwise fashion of performing an intraoral ultrasound guided PTA I&D and how to appropriately determine your landmarks. Using POCUS as an adjunct to your antibiotic and steroid therapies has the potential to benefit your patients by decreasing the need for radiation due to CT imaging, return visits, and length of stay.

Resources and other relevant articles can be found below.

References

1. Gupta G, McDowell RH. Peritonsillar Abscess. [Updated 2022 Jul 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519520/

2. Ma J., Mateer R, Reardon R., Byars D., Knapp B., Laudenbach A.. Soft Tissue Infections. Emergency Ultrasound. Fourth ed. McGraw Hill; 2014:529-531:chap 22. 

3. Costantino TG, Satz WA, Dehnkamp W, Goett H. Randomized Trial Comparing Intraoral Ultrasound to Landmark-based Needle Aspiration in Patients with Suspected Peritonsillar Abscess. Academic Emergency Medicine. 2012;19(6):626-631. doi:https://doi.org/10.1111/j.1553-2712.2012.01380.x

4. Secko M, Sivitz A, Think ultrasound first for peritonsillar swelling, Am J Emerg Med (2015), http://dx.doi.org/10.1016/ j.ajem.2015.01.031

5. Galioto NJ. Peritonsillar Abscess. Am Fam Physician. 2017 Apr 15;95(8):501-506. PMID: 28409615.(https://www.aafp.org/pubs/afp/issues/2017/0415/p501.html)

Other great, relevant resources for further review on this topic:

https://www.thelandofem.com/blog/2019/11/18/intern-ultrasound-of-the-month

https://www.ultrasoundgel.org/posts/X_iZeT5q6pSW2I8xLfbDZQ

https://www.emrap.org/episode/ptaneedle/ptaneedle

https://www.emrap.org/episode/emraplive8/videodebut

Alexander VanFleet is a PGY2 in the Emergency Medicine residency program.

Allyson Hansen is the Ultrasound Director for USF Emergency Medicine