Original ContributionsEmergency Department Ultrasound Scanning for Abdominal Aortic Aneurysm: Accessible, Accurate, and Advantageous*
Introduction
The prevalence of abdominal aortic aneurysms (AAAs) particularly in men older than 55 years, is increasing, and deaths caused by ruptured AAAs have increased dramatically.1 Many patients who present to the emergency department with a ruptured AAA are unaware of their aneurysmal disease. Only a minority present with the classic triad of abdominal/flank pain, shock, and a pulsatile abdominal mass.2 Thus, it is not surprising that ruptured AAA is frequently misdiagnosed at the patient’s initial presentation.3 As might be expected, delays in diagnosis are often associated with disastrous consequences.4, 5
Misdiagnosis occurs more frequently in those presenting with atypical symptoms and signs.3 Patients with leaking AAAs may present with a colicky pain that radiates from the flank to the groin accompanied by hematuria. Understandably, their condition is often misdiagnosed as renal colic. Equally confounding clinical scenarios may lead to misdiagnoses such as gastrointestinal bleeding, diverticulitis, or acute myocardial infarction.
The presence of a pulsatile abdominal mass is neither a sensitive nor specific means of detecting an AAA.6, 7 A recent summary of the reported efficacy of abdominal examination indicates that palpation detects only 39% of all AAAs.6 Sensitivity improves with increases in aneurysmal diameter except in patients who are obese and those with ruptured AAAS.6 Conversely, the presence of a pulsatile abdominal mass does not invariably indicate aneurysmal disease; in one series, normotensive patients with tender pulsatile abdominal masses were most frequently found to have para-aortic masses transmitting the pulsations of a normal-caliber aorta.7 Consequently, the overall reported positive predictive value of palpating a widened aorta is only 43%.6
Hypotension, although helpful in prompting the diagnosis of AAA, is an overwhelmingly poor prognostic factor.5 Normotensive patients presenting with contained bleeding are the group most likely to survive emergency repair of a ruptured AAA.4 Hence, the onus is on the emergency physician to entertain the diagnosis of AAA before hypotension develops.
Ultrasound scanning has a well-established role as an adjunct in the diagnosis of AAA.1 Ultrasound examinations have been used in asymptomatic patients to screen for AAA and to monitor the progress of aneurysmal disease. In symptomatic patients, bedside scanning by ultrasonographers has proved an effective means of establishing or excluding the diagnosis of AAA.8 Although computed tomography (CT) and angiography are more likely to detect leaking blood, thereby distinguishing a ruptured AAA from an intact aneurysm, the combination of symptoms and the presence of an AAA on ultrasound scanning rarely results in negative findings at laparotomy.9
We believe that bedside aortic ultrasound scanning performed in the ED can serve 2 distinct purposes. First, if used as a widespread screening measure in those at risk for aneurysmal disease, it may prevent the misdiagnoses that so frequently occur. Second, in patients in whom a ruptured AAA is suspected, confirming the presence of an aneurysm by ultrasound scanning might obviate the potentially dangerous trip to the CT scanner, expedite the patient’s transport to surgery, or both.
The literature regarding the ability of emergency physicians to perform bedside scans to detect AAA is relatively limited; to our knowledge, there is only one case report detailing the clinical impact of emergency physician–performed ultrasonography for AAA.10 Our objectives in performing this study were therefore twofold: to determine whether emergency physicians with relatively limited training and experience could accurately distinguish the presence or absence of an AAA, and to assess the potential impact of bedside aortic ultrasound scans on patient management.
Section snippets
Materials and methods
This study was conducted in the ED of an adult academic tertiary referral center serving approximately 48,000 patients per year.
After receiving approval for the study from our hospital’s institutional review board, 20 emergency physicians and emergency medicine trainees with 3 or more years of postgraduate experience attended a 3-day ultrasound training course. None of the participants had any prior experience performing or interpreting ultrasound scans. The course was developed, following
Results
Between September 1997 and December 1999, we performed 68 bedside aortic scans. The results of these scans were compared with CT scans in 28 patients, with formal ultrasound studies in 19, angiography in 1, and laparotomy in 9. In the remaining 11 instances, the radiologist’s review of the videotaped scans served as the gold standard.
The aorta was visualized in 66 of the 68 patients who had ultrasound scanning; in 2 patients (who proved not to have AAAs), overlying gas shadows obscured the
Discussion
In 1988, Shuman et al8 reported their 2-year experience “with rapid, emergent sonography performed in the emergency department.” Ultrasonographers were on call to present immediately to the ED whenever paramedics or emergency physicians requested their services for patients with abdominal or back pain, pulsatile masses, and hypotension or tachycardia. Rapid bedside ultrasonography was performed before the surgeon’s examination of the abdomen. Thirty-two of the 60 patients in their study proved
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2018, Annals of Vascular SurgeryCitation Excerpt :There were no false positives with POCUS, demonstrating a specificity of 100%. The sensitivity and specificity found in this study was similar to previous studies involving novices trained in POCUS to screen for AAA.14,20 The study performed by Blois determined that a family medicine resident trained in ultrasound to screen for AAA was highly accurate in detecting AAA in an outpatient general clinic, with a sensitivity and specificity of 100%.20
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Address for reprints: Marie Kuhn, MD, FACEM, Emergency Department, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia 5000; Australia;, +61 8 8222 5063, fax +61 8 8222 4171; E-mail [email protected].