Diagnostic ultrasound ( PDFDrive )

CHAPTER 12 The Retroperitoneum 437
A
B
FIG. 12.5 Aorta With Saccular Aneurysm. (A) Viewed in the longitudinal plane, the aorta appears normal. (B) Transverse imaging of the aorta
is required to reliably detect a saccular aneurysm. Unless a longitudinal image can be obtained in the plane of the greatest diameter of a saccular
aneurysm, transverse imaging must be used to measure the greatest diameter.
A B C
FIG. 12.6 Small Aortic Aneurysm Just Reaching 3.0 cm. (A) Longitudinal scan. Note that the abdominal aortic aneurysm was incorrectly
measured from inner wall to inner wall (calipers, 2.9 cm) instead of the correct method, which is outer wall to outer wall. (B) The patient was lost
to follow-up of the aneurysm. He returned 6 years later with a 6-week history of abdominal and back pain. The aneurysm was incidentally rediscovered
during the course of abdominal ultrasound. On longitudinal imaging, the aneurysm had increased in size (4.6 cm). (C) Transverse view shows that
the aortic lumen is actually larger and now is eccentric, with a largest diameter of 7.3 cm. In retrospect, the patient’s 6-week history of abdominal
and back pain probably had been from the contained perforation of the aneurysm.
decubitus position. he middle and distal abdominal aorta are
oten better seen in this position, particularly in obese patients.
he proximal common iliac arteries may also be better seen in this
position.
We obtain longitudinal and transverse cine loops from an
anterior window and from a let lateral window. he longitudinal
cine loops allow for easy remeasurement of the aorta by the
reviewing physician. he transverse cine loops allow the reviewing
physician to determine whether there is eccentricity of the
aneurysm.
Computed Tomography
Computed tomography (CT) has a limited role in AAA screening
and surveillance but should be used in any of the following
situations:
1. he patient is so obese or otherwise diicult to image that
whether the aneurysm may be eccentric cannot be determined
with reasonable certainty on initial scanning. Once the
aneurysm is shown to be fusiform, performing most of the
further surveillance with ultrasound is reasonable.
2. he aneurysm is known to be eccentric, and the area of
eccentricity is not optimally seen with ultrasound.
3. he patient is acutely symptomatic (including emergency
room patients).
4. Portions of the iliac arteries that are known to be aneurysmal
are not well seen.
5. he AAA is suspected to be an inlammatory AAA (described
later) and has not yet been imaged with CT.
6. he aneurysm is suspected of having reached a size at which
treatment planning is needed.