Systematic review: Emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm

Background The use of ultrasound (US) to diagnose an abdominal aortic aneurysm (AAA) has been well studied in the radiology literature, but has yet to be rigorously reviewed in the emergency medicine arena. Objectives This was a systematic review of the literature for the operating characteristics of emergency department (ED) ultrasonography for AAA. Methods The authors searched PubMed and EMBASE databases for trials from 1965 through November 2011 using a search strategy derived from the following PICO formulation: Patients - patients (18+ years) suspected of AAA. Intervention - bedside ED US to detect AAA. Comparator - reference standard for diagnosing an AAA was a computed tomography (CT), magnetic resonance imaging (MRI), aortography, official US performed by radiology, ED US reviewed by radiology, exploratory laparotomy, or autopsy results. AAA was defined as ≥3 cm dilation of the aorta. Outcome - operating characteristics (sensitivity, specificity, and likelihood ratios [LR]) of ED abdominal US. The papers were analyzed using Quality Assessment of Diagnostic Accuracy Studies (QUADAS) guidelines. Results The initial search strategy identified 1,238 articles; application of inclusion/exclusion criteria resulted in seven studies with 655 patients. The weighted average prevalence of AAA in symptomatic patients over the age of 50 years is 23%. On history, 50% of AAA patients will lack the classic triad of hypotension, back pain, and pulsatile abdominal mass. The sensitivity of abdominal palpation for AAA increases as the diameter of the AAA increases. The pooled operating characteristics of ED US for the detection of AAA were sensitivity 99% (95% confidence interval [CI] = 96% to 100%) and specificity 98% (95% CI = 97% to 99%). Conclusions Seven high-quality studies of the operating characteristics of ED bedside US in diagnosing AAA were identified. All showed excellent diagnostic performance for emergency bedside US to detect the presence of AAA in symptomatic patients.