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ABDOMINAL ULTRASOUND
For this reason, aortic aneurysms are monitored,
and a graft placed within the vessel in
aneurysms over 5 cm which are increasing in size.
Postoperative complications of grafts, such as
infection or pseudoaneurysm, are usually monitored
with CT or MRI.
Discussions of the benefits of screening programmes
for selected populations are ongoing. 1,2
However, there is some evidence that, despite the
reduction of mortality due to aneurysm rupture,
overall mortality in men over 65 remains unaffected
by screening, 3 and it has not been widely
adopted into patient management.
Most aneurysms are associated with atherosclerosis,
which weakens the media of the wall, causing
the vessel to dilate and eventually rupture.
The aneurysm may be fusiform or saccular (Fig.
8.3). Blood flow within it is turbulent, and the
slow-flowing blood at the edges of the vessel tends
to thrombose.
Surgery is always complicated by the involvement
of the renal arteries. Fortunately, the vast
majority of aneurysms are infrarenal, but it can be
difficult to determine the relationship of the
aneurysm to the renal artery origins on ultrasound,
and CT is helpful in such cases. The use of angiography
can be beneficial in this respect; however its
disadvantage is that, unlike ultrasound, it displays
only the lumen of the vessel and can underestimate
the pathology present.
Occasionally the aneurysm affects the bifurcation
and common iliac arteries, which should be
examined during the scan as far as possible.
The true maximum diameter of the aneurysm
should be ascertained in TS and LS. A true anteroposterior
diameter is most accurately measured
in LS, by ensuring the calipers lie in a plane perpendicular
to the vessel axis at its widest part. To measure
the lateral diameter in TS, care must be taken to
keep the angle of the transducer perpendicular to the
vessel axis to ensure an accurate and reproducible
measurement. The ability of ultrasound to locate the
B
A
C
Figure 8.3 (A) LS demonstrating an aneurysm of the lower abdominal aorta. (B) TS through the aneurysm containing
thrombus with an eccentric lumen demonstrating turbulent flow. (C) LS demonstrating flow around the thrombus in
the aneurysm.
(Continued)