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.