POCUS

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

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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