US Aorta Abdomen Transabdominal US of the abdominal aorta poses negligible risk to patients and can reliably detect the presence of an AAA in nearly all patients with sensitivity and specificity approaching 100% [3,9,10,16]. With the portability of US machines, sonographic evaluation of the abdominal aorta can be performed in a wide range of settings, including in the emergency department [16,41]. US of the abdominal aorta is the mainstay imaging procedure for AAA screening and surveillance [7,12,16,42,43] and is often the first-line imaging study performed for evaluation of asymptomatic patients suspected to have an AAA [9,10,16,44]. In 1% to 2% of cases, the abdominal aorta cannot be adequately evaluated by US because of large patient body habitus or excessive overlying bowel gas [14,45]. Pre-evaluation overnight fasting is recommended to reduce bowel gas in patients [3,10,16]. Compared to CT, US underestimates AAA diameters by an average of 1 to 3 mm [15,16,54-56]. For preintervention planning for AAA endovascular or surgical repair, US is insufficiently precise and does not provide imaging information on access vessels and abdominal aortic branches [7,13]. A CTA, or alternatively MRA, is needed when the size threshold for repair is reached [10,13,44]. To overcome variations in imaging plane orientation that can occur with conventional 2-D US, 3-D US has shown promise for improved accuracy and reproducibility in aortic diameter measurements by allowing for measurements to be made in the plane orthogonal to the centerline of the abdominal aorta [57,58]. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www. acr.org/ac.
Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm. US Aorta Abdomen Transabdominal US of the abdominal aorta poses negligible risk to patients and can reliably detect the presence of an AAA in nearly all patients with sensitivity and specificity approaching 100% [3,9,10,16]. With the portability of US machines, sonographic evaluation of the abdominal aorta can be performed in a wide range of settings, including in the emergency department [16,41]. US of the abdominal aorta is the mainstay imaging procedure for AAA screening and surveillance [7,12,16,42,43] and is often the first-line imaging study performed for evaluation of asymptomatic patients suspected to have an AAA [9,10,16,44]. In 1% to 2% of cases, the abdominal aorta cannot be adequately evaluated by US because of large patient body habitus or excessive overlying bowel gas [14,45]. Pre-evaluation overnight fasting is recommended to reduce bowel gas in patients [3,10,16]. Compared to CT, US underestimates AAA diameters by an average of 1 to 3 mm [15,16,54-56]. For preintervention planning for AAA endovascular or surgical repair, US is insufficiently precise and does not provide imaging information on access vessels and abdominal aortic branches [7,13]. A CTA, or alternatively MRA, is needed when the size threshold for repair is reached [10,13,44]. To overcome variations in imaging plane orientation that can occur with conventional 2-D US, 3-D US has shown promise for improved accuracy and reproducibility in aortic diameter measurements by allowing for measurements to be made in the plane orthogonal to the centerline of the abdominal aorta [57,58]. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www. acr.org/ac.