POCUS

What is that Hot Potato Voice? POCUS for the PTA

The Case:

A 25-year-old male with recurrent strep throat presents to the ED with sore throat, difficulty swallowing, and feeling as though his voice has changed.  His physical exam is significant for a left sided, bulging tonsil.  He is currently managing his own secretions, and his respiratory status is stable.  You are concerned that he has not been able to drink any fluids since the night prior.  He appears well hydrated, but you question if this is simple tonsillar cellulitis or a peritonsillar abscess (PTA).  You know that clinical diagnosis of PTA only has a reported sensitivity of 78% and a specificity of only 50% (Lyon et al, 2005) and want to do further diagnostic imaging.  Should this patient go to CT, or could you find an answer faster at the bedside with much less radiation? Can you drain this in the emergency department or does he need to proceed to the OR with ENT? He has gotten viscous lidocaine and his pain improved. His rapid strep was positive. You wheel out your bedside ultrasound and perform an intraoral ultrasound.

Using the endocavitary probe, you perform the following US of the peritonsillar region:

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Question:

What is the diagnosis?

Peritonsillar abcess
T - Tonsil, PTA - Abscess, Arrow - Carotid

T - Tonsil, PTA - Abscess, Arrow - Carotid

Point of Care PTA Ultrasound:

There are two techniques for performing an ultrasound of the tonsils - transcutaneous and intraoral.

Transcutaneous Ultrasound: This technique is useful in children, especially if performing a needle aspiration of the abscess, as it is less invasive and leaves spaces for aspiration equipment in the oral cavity.  Using the linear high frequency transducer, positioned under the mandible with your probe marker towards the patient’s earlobe on the same side, first identify the submandibular gland, and then the tonsil, immediately deep to the submandibular gland.

Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections."  Pediatric Radiology  46.7 (2016): 1059-067.

Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections." Pediatric Radiology 46.7 (2016): 1059-067.

Arrow - Vasculature (Carotid and IJ), SMG - Submandibular gland, T - Tonsil

Arrow - Vasculature (Carotid and IJ), SMG - Submandibular gland, T - Tonsil

Intraoral Ultrasound: As used in the case, this technique utilizes an endocavitary transducer after numbing the area with topical anesthetic for patient comfort. The transducer is placed intraorally abutting the area of suspected abscess with the probe marker facing the ipsilateral ear.

Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department."  Academic Emergency Medicine  12.1 (2005): 85-88.

Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department." Academic Emergency Medicine 12.1 (2005): 85-88.

The tonsil is identified by the irregular surface, representing tonsillar crypts. An isoechoic ring surrounding an anechoic region identifies an abscess with posterior enhancement.  Abscesses will develop in between the medial aspect of the tonsil and superior constrictor muscles.  Posterior and lateral to the tonsil is the important internal carotid artery, which can be seen with pulsatile flow on color Doppler.  It is important to identify this structure prior to draining of the abscess.  It will run anterior to the jugular vein within the carotid sheath.

T - Tonsil, PTA - Peritonsilar abscess, Arrow - Carotid  Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.”  Am J Emerg Med  (2015).

T - Tonsil, PTA - Peritonsilar abscess, Arrow - Carotid

Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.” Am J Emerg Med (2015).

Peritonsillar Abscess on Ultrasound:

  • Intraoral sensitivity ranges from 90-100%

  • Transcutaneous sensitivity ranges from 80-91%

  • Enlarged tonsils with:

    • Heterogenous, cystic, anechoic fluid

    • Well circumscribed with irregular margins

  • Usually along the posterolateral aspect of tonsil

  • Can save a patient from the radiation of a CT scan (where sensitivity is 100%, but specificity is 75%)

 

Back to our case:

Can you find an answer to your patient’s symptoms quickly, at the bedside?

  • Yes! You should think of ultrasound to help you diagnose a PTA, which in the published literature has a comparable sensitivity to CT (see above)

Do you need an ENT and to send this patient to the OR?

  • Case reports suggest that US assisted drainage can replace CT and operative drainage of abscesses (Todsen et al. 2018), but a true trial comparing the two modalities is yet to be completed

  • It never hurts to use your ultrasound to determine what you can see!

 

References:

  1. Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections." Pediatric Radiology 46.7 (2016): 1059-067.

  2. Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department." Academic Emergency Medicine 12.1 (2005): 85-88.

  3. McLario, David J., and John L. Kendall, eds. Case Studies in Pediatric Emergency and Critical Care Ultrasound. Cambridge: Cambridge UP, 2013. Print.

  4. Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.” Am J Emerg Med (2015).

  5. Todsen, Tobias, Stage, Mads G., Hahn, Christoffer H. “A Novel Technique for Intraoral Ultrasound-Guided Aspiration of Peritonsillar Abscess.” Diagnostics 8.3 (2018)

AEM Early Access 22: Test Characteristics of Point of Care Ultrasound for the Diagnosis of Retinal Detachment in the Emergency Department

Welcome to the twenty-second episode of AEM Early Access, a FOAMed podcast collaboration between the Academic Emergency Medicine Journal and Brown Emergency Medicine. Each month, we'll give you digital open access to an recent AEM Article or Article in Press, with an author interview podcast and suggested supportive educational materials for EM learners.

Find this podcast series on iTunes here.

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DISCUSSING (CLICK ON LINK FOR FULL TEXT, OPEN ACCESS THROUGH January 31):

Test Characteristics of Point of Care Ultrasound for the Diagnosis of Retinal Detachment in the Emergency Department. Daniel J. Kim, MD,  Mario Francispragasam, MEd, MD, Gavin Docherty, MD, Byron Silver, MSc, MD, Ross Prager, BSc, Donna Lee, MD, RDMS, and David Maberley, MSc, MD. 

LISTEN NOW: FIRST AUTHOR INTERVIEW WITH Daniel J. Kim, MD

Profile Shot [Daniel Kim].jpg

Daniel J. Kim, MD

Department of Emergency Medicine

Vancouver General Hospital

Director, Ultrasound Fellowship Program

University of British Columbia

@dan___kim

ABSTRACT

Previous studies of point of care ultrasound (POCUS) have reported high sensitivities and specificities for retinal detachment (RD). Our primary objective was to assess the test characteristics of POCUS performed by a large heterogeneous group of emergency physicians (EPs) for the diagnosis of RD.

Methods: This was a prospective diagnostic test assessment of POCUS performed by EPs with varying ultrasound experience on a convenience sample of emergency department (ED) patients presenting with flashes or floaters in one or both eyes. After standard ED assessment, EPs performed an ocular POCUS scan targeted to detect the presence or absence of RD. After completing their ED visit, all patients were assessed by a retina specialist who was blinded to the results of the POCUS scan. We calculated sensitivity and specificity with associated exact binomial confidence intervals (CI) using the retina specialist's final diagnosis as the reference standard.

Results: A total of 30 EPs enrolled 115 patients, with median age of 60 years and 64% female. The retina specialist diagnosed RD in 16 (14%) cases. The sensitivity and specificity of POCUS for detecting RD was 75% (95% CI 48%-93%) and 94% (95% CI 87%-98%), respectively. The positive likelihood ratio was 12.4 (95% CI 5.4-28.3), and negative likelihood ratio was 0.27 (95% CI 0.11-0.62).

Conclusions: A large heterogeneous group of EPs can perform POCUS with high specificity but only intermediate sensitivity for RD. A negative POCUS scan in the ED performed by a heterogeneous group of providers after a one-hour POCUS didactic is not sufficiently sensitive to rule out RD in a patient with new onset flashes or floaters. This article is protected by copyright. All rights reserved.

ADDITIONAL RELATED READING

Vrablik et al, 2015. The diagnostic accuracy of bedside ocular ultrasonography for the diagnosis of retinal detachment: a systematic review and meta-analysis. https://www.ncbi.nlm.nih.gov/pubmed/24680547

Jacobsen et al, 2016. Retrospective Review of Ocular Point-of-Care Ultrasound for Detection of Retinal Detachment: https://www.ncbi.nlm.nih.gov/pubmed/26973752

Baker et al, 2017. Can emergency physicians accurately distinguish retinal detachment from posterior vitreous detachment with point-of-care ocular ultrasound?: https://www.ncbi.nlm.nih.gov/pubmed/29042095

AEM Commentary on this paper: https://www.ncbi.nlm.nih.gov/pubmed/30112843

Other commentaries on this paper:

NEJM Journal Watch: https://www.jwatch.org/na46896/2018/06/11/dont-try-rule-out-retinal-detachment-with-poc-ultrasound

UC San Diego Ultrasound Division: http://emultrasound.sdsc.edu/index.php/2018/07/25/retinal-detachment/

Ultrasound Case of the Month

Case: Submitted by Dr. Sam Goldman

This is an 83-year old woman with a history of prior abdominal surgeries presenting to the ED as a transfer from her SNF with increasing abdominal distention. Patient has not had a bowel movement in four days although endorses passing occasional flatus. She denies emesis though endorses nausea, hiccupping, and burping. She denies any abdominal pain, fevers, chills, dysuria or urinary frequency. 

Diagnosis:

Small Bowel Obstruction

Image was acquired with the curvilinear probe, but any high penetration probe (eg curvilinear of phased array probe) can also be used.  Multiple regions of the abdomen should be interrogated when evaluating for SBO.

What are we looking for with abdominal US for SBO?

When evaluating for an SBO, we are looking for fluid filled small bowel loops >2.5-3cm in width. You maybe more likely to see an increase in intestinal contents (fluid and echogenic materials) and you may see to-and-fro or whirling of the intestinal contents. In more severe cases, you may see bowel wall thickening (greater than 3mm) and free fluid which is extraluminal. pSBO may be more difficult to evaluate with the US machine.   

What do we see in this video?

  • Dilated loops of bowel > 2.5cm measured outer wall to outer wall (most sensitive and specific finding). 
  • Bidirectional flow of bowel contents (to and fro or whirling)
  • Visualization of plicae circularis (“keyboard sign”)

How good is U/S for Detecting SBO?

Ultrasound is superior to abdominal plain films and approaches the sensitivity and specificity of CT scan in many cases. 

Sensitvity Specificity
Abdominal Films 66-77% 50-57%
CT 92% 93%
Ultrasound 88% 96%

Faculty Reviewer: Dr. Kristin Dwyer

References

(Mallo RD, et al. Computed tomography diagnosis of ischemia and complete obstruction in small bowel obstruction: a systematic review. Journal Gastrointestinal Surgery. 2005. May-Jun;9(5):690-4.)

(Ogtata M, et al. Prospective Evaluation of Abdominal Sonography for the Diagnosis of Small Bowel Obstruction. Annals of Surgery. 1996. 23(3):237-241.) 

Additional resources:

Podcast on US of SBO from www.ultrasoundpodcast.com: Episode 36 - Small Bowel Obstruction - Ultrasound Podcast

Great view of Plicae Circularis (“Keyboard Sign”) from Emory University