Diagnostic ultrasound ( PDFDrive )

CHAPTER 12 The Retroperitoneum 439
A
B
C
D
FIG. 12.8 Ruptured Abdominal Aortic Aneurysm (AAA). The use of both (A) ultrasound and (B) computed tomography (CT) in suspected
rupture of AAA should be avoided because of the addition of time for the workup. (In this case 45 minutes elapsed between the ultrasound and
CT.) CT is preferred in this setting because it can usually be done expeditiously and more reliably answers the pertinent questions. (C) Transverse
ultrasound and (D) contrast-enhanced CT show the same AAA visualized at the site of rupture. The patient did not survive.
low into the aneurysm sac through an aortic branch, usually
the IMA or a lumbar artery (Fig. 12.11, Videos 12.1 and 12.2).
In a type 3 leak, there is disruption of the integrity of the stent
grat, caused by a fabric tear or a separation of component parts
of the modular stent grat (Fig. 12.12, Videos 12.3 and 12.4). A
type 4 leak is caused by porosity of the stent grat fabric with
blood actually going through the pores in the fabric. his is seen
only early ater placement and is self-correcting. he term
endotension refers to an aneurysm sac that stays pressurized in
the presence of a stent grat. his is sometimes referred to as a
type 5 endoleak. Its presence is inferred by continued growth
in the aneurysm sac size in the absence of detecting another
type of leak. 40,41
With an endoleak, a treated aneurysm may continue to grow
and eventually rupture. Endoleaks occur in approximately onethird
of AAAs treated with stent grats. 42 Types 1 and 3 endoleaks
require immediate treatment when diagnosed. Type 4 endoleaks
are generally seen only during placement of the stent grat and
are self-limited, requiring no treatment. More judgment is involved
in the care of type 2 leaks. Small leaks may be watched over time
to see if they resolve and whether expansion of the aneurysm
occurs. 42,43
Because of the possibility of endoleaks, AAAs treated with
stent grats undergo routine imaging surveillance. Imaging most
oten includes yearly, contrast-enhanced, multiphase CT
examinations. his regular imaging greatly increases cost and
exposes patients to contrast and substantial radiation. Color
duplex Doppler sonography alone can be used to visualize
endoleaks. Several studies suggest that standard color duplex
Doppler ultrasound may be the preferred method of surveillance.
44,45 Studies comparing contrast-enhanced duplex with
standard color duplex have found the addition of contrast
improves the quality of the study. Several studies suggest that
contrast-enhanced ultrasound is at least as sensitive as CT for
the detection of endoleaks. 46-48 he issue is still a topic of research, 49
although with more experience, contrast-enhanced ultrasound
likely will play a signiicant role in AAA endoluminal grat
surveillance.
As already mentioned, surveillance for grat migration is also
necessary ater EVAR. In those undergoing surveillance for
endoleak with color duplex Doppler sonography, plain radiography
can be used to assess for grat migration.
OTHER ENTITIES CAUSING
ABDOMINAL AORTIC DILATION
Inlammatory Abdominal Aortic Aneurysm
Inlammatory AAAs constitute as much as 5% or more of all
AAAs. 50 According to some investigators, inlammatory AAA
is likely related to retroperitoneal ibrosis (see later discussion),