AAA Screening

Published on November 2016 | Categories: Documents | Downloads: 27 | Comments: 0 | Views: 182
of 7
Download PDF   Embed   Report

Good Doc about AAA screening

Comments

Content

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

Official reprint from UpToDate®
www.uptodate.com ©2015 UpToDate®

Screening for abdominal aortic aneurysm
Author
Emile R Mohler III, MD

Section Editor
Joann G Elmore, MD, MPH

Deputy Editor
Lee Park, MD, MPH

All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Jun 2015. | This topic last updated: Jun 01, 2015.
INTRODUCTION — An aneurysm is a focal dilation of a blood vessel with respect to the original or adjacent artery. An
abdominal aortic aneurysm (AAA) is defined as a dilated aorta with a diameter at least 1.5 times the diameter measured
at the level of the renal arteries. In most individuals, the diameter of the normal abdominal aorta is approximately 2.0 cm
(range 1.4 to 3.0 cm). For practical purposes, an AAA is diagnosed when the aortic diameter exceeds 3.0 cm [1,2].
The majority of aneurysms never rupture, but when they do, sudden death from retroperitoneal or intraperitoneal
exsanguination is usual unless surgery is performed immediately. Acute AAA rupture is one of the most dramatic
emergencies in medicine, particularly because it often masquerades as another problem. In the United States, ruptured
AAA is estimated to cause 4 to 5 percent of sudden deaths and is the thirteenth most common cause of death [3].
The increasing use of computed tomography and magnetic resonance imaging has revealed asymptomatic and
previously undiagnosed AAAs. The concern raised by people who become incidentally aware of a "ticking bomb" in their
abdomen presents a common dilemma to clinicians. The decision to perform elective surgery to prevent aneurysm
rupture must be weighed against immediate surgical risks in an often older adult population and the low likelihood that a
rupture will occur before death from other causes [4]. The trade-off between present and future risk should involve
patient preference as an important consideration in the decision to screen for an AAA. (See "Management of
asymptomatic abdominal aortic aneurysm", section on 'Introduction' and "Management of asymptomatic abdominal
aortic aneurysm".)
The dilemmas associated with the incidental discovery of an AAA make decisions regarding screening difficult.
Systematic population screening would yield many previously undiagnosed small aneurysms that are unlikely to rupture,
resulting in needless disease labeling [5]. Only aneurysms of a certain size would be considered for surgery, with smaller
aneurysms subject to watchful waiting.
Issues related to screening for AAAs will be reviewed here. Details regarding the clinical manifestations, diagnosis, and
treatment of AAAs are presented separately. (See "Clinical features and diagnosis of abdominal aortic aneurysm" and
"Management of asymptomatic abdominal aortic aneurysm", section on 'Introduction'.)
EPIDEMIOLOGY AND RISK FACTORS — The epidemiology and risk factors related to abdominal aortic aneurysm
(AAA) are discussed in detail elsewhere. (See "Epidemiology, risk factors, pathogenesis and natural history of abdominal
aortic aneurysm", section on 'Epidemiology' and "Clinical features and diagnosis of abdominal aortic aneurysm", section
on 'Risk factors'.)
In summary, the most important risk factors for AAA are increasing age, smoking, and male sex:
● The prevalence of AAAs is negligible in individuals under the age of 60, particularly women, but then increases
dramatically with age [1,6,7]. Screening studies show that AAA occurs in 4 to 9 percent of individuals over the age
of 60 [8-11]. However, most (57 to 88 percent) of these aneurysms are ≤3.5 cm in diameter. Clinically important
aneurysms over 4.0 cm in diameter are present in about 1 percent of men between the ages of 55 and 64; the
prevalence increases by 2 to 4 percent per decade thereafter [6,7]. On the basis of population surveillance data
over 20 years from a screening program in Gloucestershire, United Kingdom, it appears that the mean aortic
http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 1 of 7

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

diameter and incidence of aortic aneurysm in men has been declining since the program inception in 1990 [12].
● It has been estimated that smoking accounts for 75 percent of all aneurysms ≥4.0 cm in diameter [13]. Studies
indicate that the prevalence of AAA in individuals over 65 years appears to be decreasing [14,15], and this
decrease has been correlated with trends in cigarette smoking [16].
● AAAs are four to six times more common in men than in women [17,18]. In addition, AAAs develop in women
about ten years later than in men [19]. A model to identify women with multiple cardiovascular risk factors who are
at particularly high risk for AAA and may benefit from screening has been developed combining two US data sets,
but remains to be validated in other populations [20].
A positive family history is another factor that significantly increases the risk of AAA [21]. In a study that did not have a
clear definition of a positive family history, a patient report of a positive family history doubled the risk for AAA [21]. A
clear history of surgery for an AAA in a first-degree relative may increase the risk four-fold [22].
In addition, a number of other predictors of AAA have been identified [13,20].
● White race
● Atherosclerosis, especially peripheral artery disease
● Hypertension
● Aneurysms of the femoral or popliteal arteries
● Obesity
Regular exercise and a diet rich in fruit, vegetables, and nuts reduce the risk of AAA [20].
NATURAL HISTORY AND MANAGEMENT — The following observations have been noted regarding the natural history
of abdominal aortic aneurysms (AAAs) (see "Management of asymptomatic abdominal aortic aneurysm", section on
'Aneurysm diameter and rupture risk'):
● Only 1 percent of 65-year-old men who have a negative ultrasound will develop an AAA in the next five years [23].
● Aneurysms less than 4.0 cm in transverse diameter are unlikely to rupture in the next five years [24,25].
● The five-year overall cumulative rupture rate of incidentally diagnosed aneurysms in population-based samples is
25 to 40 percent for aneurysms larger than 5.0 cm, compared with 1 to 7 percent for aneurysms 4.0 to 5.0 cm
[24,26-28].
Management options for patients with an asymptomatic AAA include surgery, endovascular stenting, and watchful
waiting. (See "Management of asymptomatic abdominal aortic aneurysm" and "Endovascular repair of abdominal aortic
aneurysm" and "Management of asymptomatic abdominal aortic aneurysm", section on 'Introduction'.)
The case-fatality rate is 50 percent when surgery is performed emergently on the 40 percent of patients with ruptured
aneurysms who survive long enough to come to medical attention [29-31]. This contrasts with mortality for elective repair
that is reported to be between 1 and 5 percent, depending upon comorbidities and the type of repair [3]. (See
"Management of symptomatic (non-ruptured) and ruptured abdominal aortic aneurysm", section on 'Introduction'.)
SCREENING TESTS — Asymptomatic abdominal aortic aneurysms (AAAs) can be detected on physical examination or
by imaging studies. Abdominal ultrasonography is considered the screening modality of choice for AAAs because of its
high sensitivity and specificity, as well as its safety and relatively low cost.
Abdominal ultrasonography — Ultrasonography has been used as the screening modality in the large randomized
trials of screening for AAA. With a sensitivity of 95 to 100 percent and a specificity of nearly 100 percent [32],
ultrasonography has superb test characteristics for diagnosing and following an AAA. (See "Clinical features and
http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 2 of 7

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

diagnosis of abdominal aortic aneurysm", section on 'Imaging asymptomatic patients'.)
Physical examination — The aorta bifurcates at the umbilicus. Thus, physical examination in a patient with an AAA
may reveal a pulsatile mass in the epigastrium. The accuracy of the clinical examination is markedly diminished by
obese body habitus and smaller aneurysm size [33]. The reproducibility of physical examination findings between
clinicians has not been studied. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on
'Abdominal palpation'.)
Use of abdominal palpation for screening purposes has been evaluated in several populations. One report of
asymptomatic, high-risk internal medicine clinic attendees found an aneurysm prevalence of 9 percent [34]. Using
ultrasonography as the gold standard, the sensitivity of abdominal palpation varies from 23 to 68 percent, and specificity
from 75 to 91 percent [34-36]. Sensitivity increases with the size of the aneurysm and decreased abdominal girth. In one
study, the sensitivity was 61 percent for AAAs 3.0 to 3.9 cm, 69 percent for aneurysms 4.0 to 4.9 cm, and 82 percent for
aneurysms 5.0 cm or greater; when girth was less than 100 cm, sensitivity was 100 percent for aneurysms 5.0 cm or
larger [36]. The predictive value of palpation declines dramatically below age 70 [37,38].
Other imaging modalities — AAAs may be seen on plain films of the abdomen, abdominal computed tomography
(CT), and magnetic resonance imaging (MRI). Both CT and MRI appear to be highly accurate tests for AAAs but are not
generally performed for screening as they are more expensive than abdominal ultrasonography. However, nearly twothirds of aneurysms leading to surgery are detected as incidental findings on imaging studies (most often CT or MRI)
that are performed for other indications [3]. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section
on 'Diagnosis'.)
EFFECTIVENESS OF SCREENING
Effectiveness — The effectiveness of population-based screening for abdominal aortic aneurysms (AAAs) with
abdominal ultrasonography has been evaluated in large randomized trials and systematic reviews [17,21,39-45].
The Multicenter Aneurysm Screening Study (MASS), the largest of the randomized trials, evaluated a population-based
sample of 67,800 men between the ages of 65 and 74 [39]. Subjects were randomly assigned to receive an invitation to
undergo ultrasound screening or no correspondence. Of the 33,839 men invited to undergo screening, 80 percent were
tested. The prevalence of aortic aneurysms (defined as maximum aortic diameter ≥3.0 cm) was 4.9 percent (1333
aneurysms). Repeat ultrasonography was performed yearly in those with an aortic diameter of 3.0 to 4.4 cm and every
three months with an aortic diameter of 4.5 to 5.4 cm. Patients were referred for urgent surgery at an aortic diameter
≥5.5 cm, an increase in aortic diameter by more than 1 cm in a year, or symptoms attributed to the aneurysm. Surgery
was performed significantly more often in the screened group (354 versus 146 patients in the control group).
A decrease in aneurysm-related deaths (30-day mortality from surgery and deaths from ruptured aneurysms) for the
screened group, compared with the control group, was seen at four-year follow-up (0.49 versus 0.85 per 1000 person
years, hazard ratio [HR] 0.58, 95% CI 0.42-0.78) and sustained with follow-up through 7, 10, and 13 years [46-48].
Significant reductions in all-cause mortality (HR 0.96, 95% CI 0.93-1.00) as well as AAA-related mortality were first
demonstrable at the seven-year follow-up [46]. In the final data analysis from this trial, at 13 years, there was a 42
percent reduction (95% CI 31-51 percent) in aneurysm-related deaths, with an estimation of 216 men needing to be
invited for screening to save one death over 13 years [48]. The overall reduction in all-cause mortality was 3 percent (CI
1-5 percent). There were twice as many elective operations for AAA and half as many emergency operations in the
invited group compared to the control group. Among 25,541 men with a normal first scan, there were a total of 59
ruptured abdominal aneurysms, with most ruptures occurring after eight years of follow-up and in men whose initial scan
showed an aortic diameter 2.5 to 2.9 cm; whether rescreening is indicated for this population at some subsequent
interval (possibly six to seven years after the initial examination) would require further investigation. Additionally, it
should be noted that the rate of ruptured aortic aneurysm in the population has been declining since the initiation of

http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 3 of 7

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

MASS, even in the absence of screening [49].
Results 20 years after initiation of a screening program for 65-year-old men in Gloucestershire, England, are available
[12]. Nearly 62,000 men were invited for screening, and 85 percent participated. One hundred and forty-eight of 52,690
screenees had an initial aortic diameter >5.4 cm and were referred for treatment; 4.6 percent had a diameter 2.6 to 5.4
cm and underwent surveillance. Perioperative mortality for the 631 surgeries performed on screen-detected aneurysms
was 3.9 percent; an additional 372 procedures were performed for aneurysms detected incidentally with a perioperative
mortality of 6.7 percent. The number of ruptured aneurysms fell annually during the course of the program in
Gloucestershire.
A systematic review and two meta-analyses analyzed four randomized trials of population-based screening for AAA in
people over age 65, including long-term follow-up data from the MASS trial [43,45,50]. The analyses concluded that an
invitation to attend a screening for AAA significantly reduces the risk of AAA-related mortality by about 45 to 50 percent
in men ages 65 to 74. However, there was no significant reduction in all-cause mortality [45]. Lack of impact on all-cause
mortality likely relates to the relative infrequency of AAA as a cause of death (accounting for less than 3 percent of
deaths) in this older age population with multiple comorbidities.
Only one study examined population-based screening in women, a population in whom the prevalence of AAA is
significantly lower than in men (1.3 versus 7.6 percent) [17]. Screening had no effect on AAA-related mortality (OR 1.0,
95% CI 0.14-7.07) or all-cause mortality (OR 1.05, 0.92-1.19) at five-year [17] and 10-year follow-up [51].
Cost-effectiveness — An early cost-effectiveness analysis, based upon relatively short-term (four-year) follow-up of the
MASS trial data, suggested a high cost for a quality-adjusted life-year (QALY) [52]. Subsequent data indicate
incremental cost-effectiveness with longer follow-up, as would be anticipated with major expense up front for surgical
intervention, and sustained long-term benefit [46,47,53-55]. Cost-effectiveness based on seven-year follow-up in men
was estimated at $19,500 per life-year gained based upon AAA mortality, and $7600 per life-year gained based on all
cause mortality [46]. Cost-effectiveness still remains in modeling studies that account for the decreasing prevalence of
AAA and newer surgical approaches [54,55].
Screening high-risk populations — The rate of rise in prevalence of AAAs with age is increased in people who have
ever smoked, compared to nonsmokers [13]. In a modeling study, inviting only those men aged 65 to 74 years with a
history of ever smoking (accounting for 69 percent of men in this age group) for one time screening would account for 89
percent of the anticipated reduction in AAA-related mortality [21]. Modeling studies have also found that screening
strategies that incorporate only the risk factors of age, sex, and lifetime smoking history outperform strategies that
consider other risk factors.
HARM FROM SCREENING — Abdominal ultrasonography has no known inherent risks. Potential harms from screening
for abdominal aortic aneurysm (AAA) include psychological distress and adverse outcomes from management of the
AAA [56].
Psychological distress — Psychologic harm from screening is of particular concern in patients found to have small
AAAs that do not require immediate intervention.
● In a study from Denmark, men found to have a small AAA on screening had lower quality of life (QOL) scores,
mainly related to poorer health perception [57]. During a period of conservative management, the QOL scores
declined further, mainly due to worsening health perception and psychosomatic distress. The entire group of men
who were attending screenings also had a lower QOL than the controls; however, once men were found to not
have an AAA, their QOL increased beyond that of the controls, suggesting that screening caused transient anxiety
even in healthy men.
● Six weeks after screening, participants in the MASS study who were found to have an AAA had slightly higher
http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 4 of 7

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

anxiety scores, slightly lower SF-36 mental and physical health scores, and lower self-rated health than
participants whose screen result was negative [39].
Taken together, these results suggest that screening for AAA produces mild transient anxiety in the people screened.
Men found to have an AAA that does not require immediate intervention may experience declines in self-perceived
health.
Complications of treatment — Complications of AAA repair are common and can be severe [58]. (See "Open surgical
repair of abdominal aortic aneurysm", section on 'Morbidity and mortality' and "Complications of endovascular abdominal
aortic repair".)
Patients who undergo screening and are managed surgically are at risk for immediate harms (surgical complications,
hospitalization, death) while harm from an AAA rupture would occur at some future point in time. The perioperative (30day) mortality rate with elective AAA repair in major randomized trials varied from 2.7 to 5.8 percent, depending upon
comorbidity factors and the type of procedure [59-61].
A separate issue is the relative mortality in patients undergoing elective open surgery compared to endovascular repair.
This issue is discussed in detail separately. (See "Management of asymptomatic abdominal aortic aneurysm", section on
'Open versus endovascular aneurysm repair' and "Endovascular repair of abdominal aortic aneurysm".)
MAJOR SOCIETY AND GOVERNMENTAL GUIDELINES AND POLICIES
The USPSTF — The United States Preventive Services Task Force (USPSTF) makes the following recommendations
[62]:
● Men who are ages 65 to 75 and who have ever smoked should be screened one time for AAA by abdominal
ultrasonography. The USPSTF found that there is little benefit to repeat screening in men who have a negative
ultrasound and that men over age 75 are unlikely to benefit from screening.
● The prevalence of AAA is very low in men ages 65 to 75 who have never smoked. However, the USPSTF
recommends that clinicians selectively offer screening for AAA in men ages 65 to 75 who have never smoked,
based on the patient’s medical history, family history, other risk factors, and personal values.
The USPSTF advises against screening women who have never smoked, but conclude that evidence is insufficient to
assess the benefits and harms of screening women aged 65 to 75 who have ever smoked [62].
Major US professional societies — In 2005, the ACC/AHA published guidelines on peripheral artery disease in
conjunction with major societies in vascular medicine, vascular surgery, and interventional radiology, including the
Society for Vascular Surgery, and the Society for Vascular Medicine [1]. These guidelines included discussions on the
diagnosis and management of AAA.
With regard to screening, the following conclusions were reached:
● It was recommended that men 60 years of age or older, who are either siblings or offspring of patients with AAAs
should undergo physical examination and ultrasound screening for the detection of aortic aneurysms.
● It was considered reasonable that men who are 65 to 75 years of age who have ever smoked should undergo a
physical examination and one-time ultrasound screening for detection of AAAs.
The Society for Vascular Surgery issued updated guidelines in 2009 recommending one-time screening for all men older
than 65 (and at 55 if family history is positive) and screening for women older than 65 who have smoked or have a family
history [63]. The guidelines cite that, although the prevalence of AAA is lower in women than men, rupture rates are
higher in women and life expectancy is longer.

http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 5 of 7

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

Canadian guidelines — The Canadian Society for Vascular Surgery recommends screening for men between age 65
and 75 who are candidates for surgery [64]. Recommendations are not to screen women >65 years on a population
basis, but to individualize screening for women with multiple risks (smoking, cerebrovascular disease, and family
history).
UK National Health Service — In the United Kingdom, a National Health Service AAA Screening Program (NAAASP)
has been funded to screen 65-year-old men for AAAs in England, and full implementation, involving 40 local programs
offering screening, is expected to be completed in April 2013 [65]. It is estimated that 300,000 new men will be invited for
screening annually.
Medicare coverage in the US
Medicare covers a one-time ultrasound study for Medicare recipients who meet the following criteria [66,67]:
● Males between 65 and 75 years of age who smoked at least 100 cigarettes
● Males or females with a family history of AAA
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond
the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and
they answer the four or five key questions a patient might have about a given condition. These articles are best for
patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient
education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade
reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to
your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and
the keyword(s) of interest.)
● Basics topics (See "Patient information: Abdominal aortic aneurysm (The Basics)".)
● Beyond the Basics topics (See "Patient information: Abdominal aortic aneurysm (Beyond the Basics)".)
SUMMARY AND RECOMMENDATIONS
● Undetected abdominal aortic aneurysm (AAA) commonly presents catastrophically with fatal rupture. (See
"Management of asymptomatic abdominal aortic aneurysm".)
● Abdominal ultrasonography is a highly sensitive and specific screening test for AAA. (See 'Abdominal
ultrasonography' above.)
● Screening for AAA in men over age 65 results in a decreased risk of AAA-related mortality; however, any absolute
benefit on overall mortality is likely to be small in people at no increased risk for AAA. (See 'Effectiveness of
screening' above.)
● Screening for AAA can lead to psychological distress, particularly in those found to have small AAAs that will be
managed conservatively. (See 'Psychological distress' above.)
● The perioperative (30-day) mortality rate with elective AAA repair in major randomized trials varied from 2.7 to 5.8
percent, depending upon comorbidity factors and the type of procedure. (See 'Complications of treatment' above.)
● In agreement with the recommendation of the USPSTF, we recommend one-time screening for AAA with
abdominal ultrasonography in men ages 65 to 75 who have ever smoked (Grade 1A). (See 'Major society and
governmental guidelines and policies' above.)

http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 6 of 7

Screening for abdominal aortic aneurysm

7/4/15, 10:43 PM

● We also suggest one-time screening for AAA in men ages 65 to 75 who have never smoked but who have a firstdegree relative who required repair of an AAA or died from a ruptured AAA (Grade 2C). Data for screening women
with a family history are not as strong, and screening should be individualized based on other risk factors and
patient preference. (See "Epidemiology, risk factors, pathogenesis and natural history of abdominal aortic
aneurysm", section on 'Epidemiology' and "Clinical features and diagnosis of abdominal aortic aneurysm", section
on 'Risk factors'.)
● If endovascular repair of AAA is proven safer than open surgical repair while achieving similar effectiveness, the
group of people for whom screening for AAA is beneficial would likely expand. (See "Management of asymptomatic
abdominal aortic aneurysm", section on 'Open versus endovascular aneurysm repair' and "Endovascular repair of
abdominal aortic aneurysm".)
Use of UpToDate is subject to the Subscription and License Agreement.
Topic 7569 Version 31.0

http://www.uptodate.com/contents/screening-for-abdominal-aortic-…archTerm=AAA&selectedTitle=3%7E125&view=print&displayedView=full

Page 7 of 7

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close