Discussion
Without rapid intervention, rAAA carries a high mortality. Using ultrasound assessment of patients in extremis may decrease time to the operating room. Unfortunately, with our patient’s co-morbidities and cardiac arrest in the field she was not a candidate for surgical repair. Nevertheless, it is important to appreciate the value of ultrasound findings of rAAA. Catalano and Siani discussed the sonographic findings of ruptured AAA in 2005. Their series included 29 patients with rAAA (either confirmed via surgery or CT scan). The findings consistent with rAAA are (1) AAA deformation, (2) Luminal thrombus inhomogeneity, (3) Clear interruption of the lumen thrombus, (4) Intraluminal floating thrombus layer, (5) Aneurysm wall interruption, (6) Para-aortic hypoechoic area adjacent to bleeding site, (7) Retroperitoneal hematoma, and (8) Hemoperitoneum.2 All of these signs, excluding AAA deformation, were noted in rAAA. There is discussion as to whether with improved sonographic technology, in the hands of an experienced user, if ultrasound could replace the need for pre-operative CT angiograms, especially in hemodynamically unstable patients.
Perioperative hypotension is a negative survival predictor for rAAA; therefore, delays in diagnosis, can increase time to operative repair and prolong hypotensive time. In 2014, Reed and Cheung studied the effect of an emergency ultrasound program to expedite time to diagnosis. Although their study may have been underpowered for statistical significance, there was an overall decrease in time to diagnosis (56 minutes vs 111 minutes).3 This is an area of further inquiry in the current literature. Excluding technical considerations, a drawback of ultrasound can be the difficulty in assessing relevant visceral and renal artery anatomy for endovascular. Although a significant portion of open AAA repairs will require supraceliac clamping, it can be more difficult to assess distal targets such as iliac artery involvement.4 With ultrasound being increasingly employed for diagnosing of complex and urgent pathology, future studies are needed to address its use for pre-operative planning in the acute setting.
Within the current literature, more comparative studies need to be performed before ultrasound can replace CT angiogram as diagnostic gold standard for rAAA. Nevertheless, POC ultrasound facilitates swift clinical decision making for immediate patient care, with the added benefit of lower cost.