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Emergency Ultrasound

Journal Summary

Point-of-Care Ultrasound for Suspected Acute Appendicitis Performs Better than Radiology-Based Ultrasound… if You are Really Good at It

Review by Michael Boniface, MD

Ultrasound-first approach to imaging in suspected acute appendicitis in adult patients? That seems to be the accepted algorithm at Antalya Training and Research Hospital in Turkey, where this bit of research comes from. This study sought to investigate the value of point-of-care sonography by emergency physicians as part of a diagnostic algorithm, as well as compare it to radiology-based sonography. The emergency medicine attending physicians were extremely experienced, having five or more years and greater than 600 scans per year, as well as participating in an additional training workshop specific to appendiceal ultrasound. Each evaluating EP assigned a pre-test probability by VAS first after history and physical examination only and again after POCUS. All patients then underwent radiology-based ultrasound, as well. CT was only utilized in patient who had a non-diagnostic radiology-based ultrasound. A total of 264 patients were included in the final analysis, 169 (64%) of whom ultimately were confirmed as having acute appendicitis. The gold standard was surgery, pathologic evaluation of the appendix, or clinical follow results. In the 169 with confirmed appendicitis, POCUS was positive in 156 compared with only 130 by radiology-based ultrasound. Final test characteristics reported a sensitivity and specificity of 92.3% and 95.8% respectively for POCUS, compared with 76.9% and 97.8% by radiology based imaging. Laparotomy was negative in 10 patients, in which POCUS was negative in seven of them and non-diagnostic in the other three.

The data and test characteristics reported by this group are extremely impressive, but there are several features which limit this study’s conclusions and generalizability to most other practice settings. The emergency physician’s test accuracy on POCUS for diagnosing acute appendicitis was far more sensitive than that of radiologists, with only a minor sacrifice to its specificity. This should not be surprising, however, given that the emergency physicians were extremely experienced operators who underwent additional training on this protocol, whereas many of the radiology-performed examinations were performed by one-year experienced radiology residents who “had completed standard education protocol for their residency.” Additionally, the authors do not report how many of the patients ultimately required CT for non-diagnostic ultrasound and the final diagnosis or disposition of this sub-group. Although the sensitivity was much higher in the POCUS group and no patient with a false positive POCUS underwent laparotomy, clinical decisions made purely on this in the absence of radiology based ultrasound or CT likely would have resulted in two or three additional non-therapeutic laparotomies. Overall, this does add to the growing body of literature that, even in adults, when you become skilled as an operator at this protocol, it can be a very effective component to incorporate into your clinical algorithm.

Gungor F, Kilic T, Akyol KC, et al. Diagnostic value and effect of bedside ultrasound in acute appendicitis in the emergency department. Acad Emerg Med. 2017 Feb 7. doi: 10.1111/acem.13169.

Strengthening the Case for Ultrasound versus Chest Radiography for Confirmation of Central Venous Catheter Placement

Review by Michael Boniface, MD

The concept of using ultrasound prior to, or in lieu of, chest radiography following line placement has been actively studied and discussed in the literature for five to seven years now. This systematic review and meta-analysis sought to examine all available relevant data to calculate pooled test characteristics for its primary outcome of ultrasound for detection of pneumothorax and catheter malpositioning. Secondarily, it evaluated feasibility, interrater-reliability, and efficiency as defined by time saving compared with chest radiography. Of the greater than 1500 articles identified by electronic search, 15 were included in final meta-analysis. This included 1,511 patients with 1,553 catheter insertions. Pooled sensitivity and specificity for detection of catheter malposition was ultimately calculated as 82% and 98%, respectively, when compared to radiography as the gold standard. The techniques for detection varied across studies, but included limited cardiac and vascular ultrasound with agitated or non-agitated rapid saline flush. There were only 12 pneumothoraces across all studies (1.1%), all of which were detected by ultrasound, whereas only ten were detected by CXR (two seen on CT). Feasibility of obtaining adequate cardiac images for confirmation of CVC placement was greater than 96% and for detection of pneumothorax was 100%. Of the studies that reported time required, confirmation occurred in 5.6 minutes by ultrasound, compared to a mean time of 63.9 minutes for chest radiograph and 143.4 minutes for formal radiograph interpretation.

The authors conclude that when a catheter is malpositioned following placement, it will be detected by ultrasound four out of every five times. While not performing as well as the gold standard, there is a marked time savings, and if malpositioning is detected, then the CVC can be expediently addressed, obviated the need for a CXR first. Not surprisingly, pneumothorax detection is highly reliable and rapid. Despite significant heterogeneity between studies included and some potential biases, overall the authors did a fantastic job of demonstrating highly favorable characteristics for this method of confirmation, with enormous potential clinical impact given the time savings to line activation in these critically ill patients.

Ablordeppey EA, Drewry AM, Beyer AB, et al. Diagnostic accuracy of central venous catheter confirmation by bedside ultrasound versus chest radiography in critically ill patients: a systematic review and meta-analysis. Crit Care Med. 2016 Dec. 5.doi: 10.1097/CCM.0000000000002188.

Lung Ultrasound in Pediatric Patients Reduces CXR Utilization, Without Missed Pneumonias!

Review by Joshua Guttman, MD

This was a randomized controlled trial looking at the feasibility and safety of performing a lung ultrasound (LUS) instead of a chest x ray (CXR) for the diagnosis of pneumonia in children. The authors randomized 191 pediatric patients (<21 years old) presenting to the ED with a concern for pneumonia to two arms. The intervention group received only a lung ultrasound, with an optional CXR at the treating physician’s discretion after the LUS. The control arm received a CXR followed by a LUS. The authors hypothesized that they could reduce the number of CXRs performed without missing any pneumonias or resulting in unscheduled healthcare visits or adverse events. Pneumonia was defined as a lung consolidation with sonographic air bronchograms. Overall, they found a 39% reduction in CXR utilization without any missed pneumonias or adverse events. In experienced sonologists (>25 LUS), they found a 60% reduction in CXR usage. Overall, they found a NNT of 2.5 to avoid 1 CXR. However, if they exclude CXRs done at the request of the parent, PCP or admitting service, there was an NNT of 1.5. Therefore, to reduce 1 CXR, 1.5 LUS needed to be performed.

This RCT was a well performed, statistically valid study which showed a very significant decrease in CXR utilization when LUS was used as a first test. This is important, as reducing CXR utilization reduces radiation, cost ($9200 in this study) and ED length of stay (30 minutes in this study). Unfortunately, the study was underpowered for safety secondary outcomes such as missed pneumonias, which is what clinicians are most concerned about when employing a relatively new test (LUS) while not utilizing the “usual” test (CXR). Despite this, the clinicians in the study very often opted to trust the LUS, and there were no reported missed pneumonias and adverse events. However, the study was done at a center with a very robust POCUS program, and therefore it is possible that physicians at this site are more comfortable relying on LUS than in other centers. While this work is promising, research that is powered for safety outcomes would likely make more physicians comfortable in foregoing CXR completely. Based on this study, it is likely reasonable to employ a shared decision making with parents on possibly forgoing CXR.

Jones BP, Tay ET, Elikashvili I, et al. Feasibility and safety of substituting lung ultrasonography for chest radiography when diagnosing pneumonia in children: a randomized controlled trial. Chest. 2016 Jul;150(1):131-138. doi: 10.1016/j.chest.2016.02.643.

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