Accuracy of emergency medicine ultrasound in the evaluation of abdominal aortic aneurysm

doi:10.1016/j.jemermed.2005.02.016

The Journal of Emergency Medicine

Volume 29, Issue 4, November 2005, Pages 455-460

Presented as an abstract at the Society of Academic Emergency Medicine Annual Meeting, St. Louis, May 2002.

https://doi.org/10.1016/j.jemermed.2005.02.016 Get rights and content

Abstract

This study assesses the accuracy of Emergency Medicine (EM) residents in detecting the size and presence of abdominal aortic aneurysms (AAAs) using EM ultrasound (EUS) compared to radiology measurement (RAD) by computed tomography (CT) scan, magnetic resonance imaging (MRI), angiography, or operative findings. There were 238 aortic EUS performed from 1999–2000; 36 were positive for AAA. The EUS finding of “AAA” had a sensitivity of 0.94 (0.86–1.0 95% confidence interval [CI]) and specificity of 1 (0.98–1.0 95% CI). Mean aortic diameter among patients with AAA identified by EUS was 5.43 ± 1.95 cm and by RAD was 5.35 ± 1.83 cm. The mean absolute difference between EUS and RAD diameters was 4.4 mm (95% CI 3.7–5.5 mm). Regression of EUS on RAD diameters is strongly correlated, with R² = 0.92. EM residents with appropriate training can accurately determine the presence of AAA as well as the maximal aortic diameter.

Introduction

In the United States, there are approximately 11,000 cases of ruptured abdominal aortic aneurysm (AAA) per year (1). Of these, it has been estimated that 30% are misdiagnosed (2). The overall mortality rate for patients with ruptured AAA is 80–95% (3, 4). Among those who survive to the hospital, the mortality rate is 50–80% (5, 6). Once patients present to the emergency department (ED), early diagnosis significantly decreases mortality from 75% to 35% (7). The sensitivity of the clinical evaluation in the detection of unruptured AAA is only 50–65% (8). Its accuracy in patients with rupture has not been studied, but is likely to be lower, because many of these patients are hypotensive or unconscious. Less than half of the patients with a ruptured AAA will present with the classic triad of abdominal pain, hypotension, and a pulsatile abdominal mass (9). For these reasons, it is essential to have a rapid and accurate diagnostic test for patients at risk for AAA presenting with symptoms suggestive of this disease.

The present study investigates the ability of emergency medicine (EM) residents to determine the presence of an AAA as well as the accuracy of AAA measurement by ultrasound as compared to measurements made by computed tomography (CT) scan, magnetic resonance imaging (MRI), or angiography conducted by the Department of Radiology.

Section snippets

Materials and methods

This study was conducted at two urban tertiary care academic medical centers with a combined annual ED volume of 60,000 patients, between October 1999 and October 2000. Patients were included if they were older than 55 years and had at least one of the following symptoms: abdominal, back, flank or chest pain, or hypotension, as well as clinical suggestion of AAA. Patients who presented with a known, stable AAA were excluded. EM residents sought to determine whether an AAA was present based on

Results

There were 238 patients enrolled in the study. Follow-up data were obtained on all of them. EUS identified aortic abnormalities in 36 patients: 34 with AAA, one with aortic dissection, and one with “large intraluminal clot.” EUS identified the remaining 202 patients as being without emergent abnormalities of the aorta. The criterion standard identified 36 AAA (in the same 36 patients identified as “abnormal” by EUS); 31 of these patients were identified by RAD and 5 in the operating room. The

Discussion

Various imaging modalities have been used to evaluate for the presence of AAA. Cross-table lateral plain radiographs were once the most widely used test to evaluate for AAA, but are not sufficiently accurate for a potentially catastrophic disease (11). Abdominal computed tomography (CT) is nearly 100% sensitive and specific and may also serve to identify alternative diagnoses. The disadvantage of CT is expense, in terms of time, personnel, and financial resources; and it necessitates the

Limitations

No mechanism existed to determine if all eligible patients were enrolled, so it is uncertain what proportion of patients who met the entry criteria was not enrolled. This may have led to selection bias. Our residents received more extensive training than may currently be the case in the average Emergency Medicine residency program, which may limit extrapolation of these results to all EM residents. There may have been some input by attending emergency physicians into EUS findings and this was

Conclusion

Emergency Medicine residents with appropriate training can accurately determine the presence of AAA. Similar to previous investigations of ultrasound in the hands of sonography technicians and radiologists, EUS accurately measures aortic diameter in patients with AAA.

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Ultrasound in Emergency Medicine is coordinated by David H. Adler, md, and Barry Simon, md, of the University of California San Francisco, San Francisco, California

Dr. Costantino is currently at Temple University School of Medicine, Philadelphia, Pennsylvania; Dr. Dean is currently at the University of Pennsylvania, Philadelphia, Pennsylvania; Dr. Bruno is currently on active duty in the U.S. Air Force.

View full text

Ultrasound in Emergency MedicineAccuracy of emergency medicine ultrasound in the evaluation of abdominal aortic aneurysm

Abstract

Introduction

Section snippets

Materials and methods

Results

Discussion

Limitations

Conclusion

J Vasc Surg

Eur J Vasc Surg

J Vasc Surg

Eur J Vasc Endovasc Surg

Eur J Vasc Endovasc Surg

Ann Emerg Med

Mortality

Epidemiology and potential for prevention of abdominal aortic aneurysm

Br J Surg

Mortality from ruptured abdominal aortic aneurysm in Wales

Br J Surg

Operation for ruptured abdominal aortic aneurysma community-wide experience

Surgery

Selective screening for abdominal aortic aneurysm with physical examination and ultrasound

Arch Intern Med

Ultrasound in Emergency Medicine
Accuracy of emergency medicine ultrasound in the evaluation of abdominal aortic aneurysm