Diagnostic ultrasound ( PDFDrive )

436 PART II Abdominal and Pelvic Sonography
AAAs of any size are entered into the database. Patients are seen
once in our interventional radiology clinic so that they can meet
the physicians and advanced practice nurses involved and can
be informed about their disease, its treatment, and how their
aneurysm is to be followed. he clinic orders all subsequent
aortic ultrasounds and monitors all results. Ater that irst visit,
all communication is by phone and by mail. he database is
monitored periodically to make sure patients keep their appointments.
When the aneurysm reaches 5.0 cm in greatest diameter,
patients again begin to be seen regularly in the clinic.
Sonographic Technique
Pertinent history should be obtained when doing surveillance
on a known aneurysm. Questions of interest are whether the
patient has back and/or abdominal pain or tenderness. hese
symptoms can be experienced by patients who have inlammatory
aneurysms. In the absence of an inlammatory aneurysm, these
symptoms are considered an indication for aneurysm repair.
he following principles apply both to screening examinations
and studies for surveillance. Evaluation of the entire infrarenal
aorta is necessary. Identifying the aortic bifurcation guarantees
that one has seen far enough distally. By identifying the celiac,
superior mesenteric, or renal arteries or the aortic hiatus of the
diaphragm, sonographers can guarantee that the proximal
examination has been carried high enough. Images should be
obtained in both transverse and longitudinal planes. he goal is
to ind the maximum diameter of the aorta, measured from
outer edge of the wall to outer edge of the opposite wall. Measurements
should be taken perpendicular to the axis of the lumen
of the aorta. To guarantee that the measurement is perpendicular,
longitudinal images are usually best for obtaining the most
accurate measurements (Fig. 12.3). he measurement includes
both the front and the back walls.
Most infrarenal aneurysms are fusiform in shape with a
relatively circular cross section. With a fusiform aneurysm,
measurement of its size taken from any longitudinal plane through
the aorta will be the same (Fig. 12.4). he walls of the aorta are
generally well seen with longitudinal imaging because they are
parallel to the face of the transducer, resulting in a strong echo
from the walls. Transverse imaging is particularly important to
identify the small proportion of aneurysms that are eccentric.
If the aneurysm is eccentric, the measurement must be taken in
the plane of the aneurysm’s eccentricity to ind the largest diameter
of the aneurysm (Figs. 12.5 and 12.6).
We routinely image patients from two windows: the anterior
abdominal midline (sagittal plane), which allows imaging of
the maximum length of the abdominal aorta, and the let lank
(near the coronal plane), with the patient in the right lateral
FIG. 12.3 Measuring Abdominal Aorta Aneurysms (AAAs). AAA
measurements from longitudinal images are usually the most accurate
and are taken perpendicular to the lumen. The measurement includes
both the front and the back walls.
A
B
FIG. 12.4 Most Abdominal Aortic Aneurysms (AAAs) Are Fusiform. When fusiform, the AAA is circular in cross section. (A) Longitudinal
and (B) transverse gray-scale sonograms show measurement of the AAA.