Diagnostic ultrasound ( PDFDrive )

CHAPTER 12 The Retroperitoneum 435
AAA-related mortality.” Based on these results, in 2005 the
USPSTF published a recommendation for one-time screening
for men aged 65 to 75 who had ever smoked. 28 In 2014 the
USPSTF issued an update reiterating this recommendation. 29
he task force also recommended selective screening based on
risk factors for men aged 65 to 75 who had never smoked. he
risk factors they referenced were older age, positive smoking
history, irst-degree relative with AAA, history of other vascular
aneurysm, coronary artery disease, cerebrovascular disease,
atherosclerosis, hypercholesterolemia, obesity, and hypertension.
he USPSTF believed the evidence to support screening for AAA
in women smokers was inconclusive and consequently made no
speciic recommendation about such screening. he USPSTF
recommended against routine screening for women who had
never smoked.
he Screening Abdominal Aortic Aneurysms Very Eiciently
(SAAAVE) Act was passed by the US Congress and signed on
February 8, 2006. Since January 1, 2007, Medicare has covered
a one-time, ultrasound screening to check for AAA in qualiied
patients. Qualiied patients are men with a history of smoking
(i.e., those who have smoked more than 100 cigarettes total during
their lives) and men and women with a family history of AAA
in a irst-degree relative. To be covered, patients must undergo
the AAA screening study as part of the Welcome to Medicare
Physical Exam and complete the screening within the irst 6
months of Medicare eligibility. Analysis of data from the irst 2
years ater the SAAVE Act was passed indicates that a minority
(<20%) of the Medicare population that was eligible for AAA
screening underwent screening. he impact of the SAAVE Act
on the rate of AAA screening during those irst 2 years was
described as modest. 30
Across the world, a few countries currently have nationwide
screening programs although several others have begun pilot
studies. National screening has been implemented in Sweden,
in all member nations of the United Kingdom (England, Scotland,
Wales, and Northern Ireland), and in the United States. Sweden
has achieved an impressive attendance rate of 85% of those eligible
for its screening program. 8
Ultrasound Approach
Screening for AAA must have high sensitivity. It is mandatory
that the entire infrarenal abdominal aorta be examined. he
screening ultrasound has one of three results: positive, negative,
or indeterminate. 31 he number of expected indeterminate exams
should be very low, much less than 5%.
here are currently two paradigms for ultrasound in the
screening of AAAs. he irst is embodied in the current guidelines
issued by the American College of Radiology (ACR) and involves
obtaining a full set of documentation images on every patient. 31
When the screening examination is positive for AAA, the recommended
images are adequate to document aneurysm size
accurately. he screening examination thus also serves as the
irst diagnostic exam. his type of screening exam is not very
diferent from a full “diagnostic” examination and is probably
the most common type in radiology departments.
he second paradigm is used by several mobile companies
ofering aneurysm screening to the general population. hese
for-proit programs are prepaid by the individuals requesting
screening; proit is based on doing a high volume of cases within
a short time, keeping cost to a minimum. It is unclear whether
adequate quality control mechanisms are in place for these exams,
which oten have only two possible results: positive and negative.
Positive exams do not result in extension of the study to be
diagnostic. Instead, a positive exam results in a recommendation
to the patient to have a diagnostic evaluation. his allows the
provider to save time and reduce cost.
he decreased cost of this type of examination ofers a potential
beneit. If the low cost of this type of service could be widely
reproduced, and if the issue of quality control were addressed,
screening that is both accurate and cost-efective could become
available for a wider segment of the population.
Unfortunately, at least some of the programs make recommendations
to their customers that cannot be supported by the
literature such as the concept of needing to screen for AAA on
a yearly basis. Screening on a yearly basis certainly will increase
the number of patients using the service and increase proit but
hardly seems to represent an disinterested attempt to improve
health care. 32 Atherosclerotic aneurysm formation is a very slow
process and there is absolutely no need for yearly screening for
someone without an aneurysm. here are some who would
question whether a second screening is ever needed if the irst
screening was performed at age 65 or later. Certainly, once a
irst well-performed screen is negative there is no justiication
for rescreening except perhaps ater many years.
Surveillance
Once an AAA is discovered, the patient moves from screening to
a surveillance program in which the aneurysm size is periodically
checked. Because an AAA tends to grow more rapidly as its
size increases, there is general agreement that a smaller aneurysm
needs to be checked less frequently than a larger one. Otherwise,
however, consensus is lacking on frequency of sonographic surveillance.
Recommendations for assessing aneurysms less than
4.0 cm in diameter range from 1 to 3 years. 33 For the U.K. Small
Aneurysm Trial, Brady et al. 34 concluded that surveillance could
be performed at intervals of 36, 24, 12, and 3 months for aneurysms
of 35, 40, 45, and 50 mm, respectively. Following this
schedule, the risk of the AAA size on recheck being greater than
55 mm would be less than 1%. Achieving a 5% rate would require
even less frequent surveillance. Society for Vascular Surgery
practice guidelines recommend surveillance at 36, 12, and 6
months for aneurysms between 3.0 and 3.4 cm, between 3.5 and
3.9 cm, and between 4.0 and 5.4 cm, respectively. hey also recommend
surveillance every 5 years for aortas between 2.6 and
2.9 cm in size. 35 It has been suggested that aortic aneurysms may
need even less frequent surveillance than what is cited above. 36
Up until several years ago, we scanned most aneurysms yearly.
Our aneurysm clinic now follows AAAs sonographically every
2 years when the aneurysm is less than 40 mm, every year for
aneurysms 40 to 44 mm, and every 6 months once the aneurysm
reaches 45 mm.
Surveillance of aneurysms lends itself well to being followed
by a database. Our interventional radiology–run aneurysm clinic
started a database in 2003 to follow AAAs. 37 Patients with known