Version May 2024
INTRODUCTION — Mortality remains high for patients who experience rupture of an abdominal aortic aneurysm (AAA), but it has dropped considerably in the past 20 years due to a variety of factors [1]. Elective AAA repair prior to the development of symptoms is the most effective means to prevent rupture and aneurysm-related sudden death.
The definition of AAA and aortic anatomy will be reviewed here together with an overview of the epidemiology, risk factors, pathogenesis, natural history, screening, clinical features and diagnosis, management, and surgical repair, with links to more detailed topics. Our recommendations for the care of the patient with AAA are consistent with those provided by the Society for Vascular Surgery guidelines, which were updated in 2018 [2]. Other types of arterial aneurysms are discussed separately. (See "Iliac artery aneurysm" and "Femoral artery aneurysm" and "Popliteal artery aneurysm".)
DEFINITIONS AND AORTOILIAC ANATOMY — Abdominal aortic aneurysm (AAA) is the most common true arterial aneurysm. A true aneurysm is defined as a segmental, full-thickness dilation of a blood vessel that is 50 percent greater than the normal aortic diameter (figure 1) [3]. False aneurysms of the abdominal aorta can also occur but are much less common and are usually due to a traumatic or infectious etiology.
In most adults, an aortic diameter >3.0 cm is generally considered aneurysmal. Normal aortic diameter varies with age, sex, and body habitus, but the average diameter of the adult human infrarenal aorta is approximately 2.0 cm; 95 percent of the adult population has an aortic diameter ≤3.0 cm [3]. Thus, for the majority of patients, an infrarenal aorta with a maximum diameter ≥3.0 cm is considered aneurysmal [3-5]. For males, diameter alone defines the presence of an AAA and predicts clinical events. However, for females, although the aorta is still considered aneurysmal when its diameter exceeds 3.0 cm, the diameter is less predictive of clinical events. An aortic size index (ASI), calculated as diameter (cm)/body surface area (m2), is more predictive of clinical events than the absolute aortic diameter in females [6].
For the purposes of this discussion:
●Small aneurysms have a diameter <4.0 cm
●Medium aneurysms have a diameter between 4.0 and 5.5 cm
●Large aneurysms have a diameter >5.5 cm
●Very large aneurysms have a diameter ≥6.0 cm
The natural history of AAA is one of progressive expansion, which is variable and depends upon aneurysm diameter and other factors, the most important of which is ongoing smoking [7].
AAAs can be described relative to the involvement of the renal or visceral vessels. Several classification schemes have been described [8-11]. We use the following definitions to describe AAA (figure 2):
●Suprarenal aneurysm – The aneurysm involves the origins of one or more visceral arteries but does not extend into the chest.
●Pararenal aneurysm – The renal arteries arise from the aneurysmal aorta, but the aorta at the level of the superior mesenteric artery is not aneurysmal.
●Juxtarenal aneurysm – The aneurysm originates just beyond the origins of the renal arteries. There is no segment of nonaneurysmal aorta distal to the renal arteries, but the aorta at the level of the renal arteries is not aneurysmal.
●Infrarenal aneurysm – The aneurysm originates distal to the renal arteries. There is a segment of nonaneurysmal aorta that extends distal to the origins of the renal arteries.
AAA most often affects the segment of aorta between the renal and inferior mesenteric arteries; approximately 5 percent involve the renal or visceral arteries. Up to 40 percent of AAAs are associated with iliac artery aneurysm(s) (figure 1) [3-5,12]. (See "Iliac artery aneurysm".)
Thoracoabdominal aneurysms originate in the chest and may involve the visceral or renal vessels (figure 3). (See "Clinical manifestations and diagnosis of thoracic aortic aneurysm".)
Anatomy — The abdominal aorta is a retroperitoneal structure that begins at the hiatus of the diaphragm and extends to its bifurcation into the right and left common iliac arteries at the level of the fourth lumbar vertebra. The posterior abdominal peritoneum covers the abdominal aorta anteriorly and is reflected onto the posterolateral duodenum at its junction with the jejunum.
The aorta lies slightly left of the midline to accommodate the inferior vena cava, which is adjacent to the aorta on its right. The branches of the aorta include (superior to inferior) (figure 4) the left and right inferior phrenic arteries, left and right middle suprarenal arteries, celiac axis, superior mesenteric artery, left and right renal arteries, left and right gonadal arteries, inferior mesenteric artery, left and right common iliac artery, middle sacral artery, and paired lumbar arteries (L1 to L4).
The common iliac artery bifurcates into the external iliac and internal iliac arteries at the pelvic inlet (figure 5). The internal iliac artery gives rise to anterior and posterior branches to the pelvic viscera and also supplies the musculature of the pelvis. The external iliac artery passes underneath the inguinal ligament to become the common femoral artery [13].
EPIDEMIOLOGY — The estimated prevalence of abdominal aortic aneurysm (AAA) in developed countries is between 2 and 8 percent and is higher in males (4 to 8 percent in those older than 50) compared with females (1 to 1.3 percent) [14]. Based on screening, approximately 1,000,000 individuals in the United States have an AAA [15]. The prevalence of AAA increases with age in both males and females, although the age-related increase is more pronounced in males [16,17]. Ultrasound screening studies have shown that 4 to 8 percent of older males have an occult AAA [18-20]. Because the incidence of AAA rises sharply in individuals over 60 years of age, the future prevalence of AAA could increase substantially in association with the aging population. Other studies suggest that a reduction in the prevalence of smoking may have the opposite effect [21,22]. (See "Epidemiology, risk factors, pathogenesis, and natural history of abdominal aortic aneurysm", section on 'Epidemiology'.)
In the 2010s, death from rupture of an AAA was estimated to occur in approximately 7000 patients per year in the United States. AAA-associated mortality has decreased by nearly 50 percent since the early 1990s. Although the specific reasons for this decline are unknown, the declining prevalence of cigarette smoking in the adult population, the increasing awareness and impact of government-sponsored screening programs for identifying early disease, and an increase in the use of endovascular repair of AAA, particularly in the older patients, all may have played a role in this decline [1,23]. (See "Epidemiology, risk factors, pathogenesis, and natural history of abdominal aortic aneurysm", section on 'Epidemiology of AAA rupture'.)
RISK FACTORS — Well-defined clinical risk factors are associated with the pathogenesis of abdominal aortic aneurysm (AAA) [14]. The most important risk factors are listed below and discussed in detail elsewhere. (See "Epidemiology, risk factors, pathogenesis, and natural history of abdominal aortic aneurysm", section on 'Risk factors for the development of AAA'.)
Risk factors associated with aneurysmal disease include:
●Older age
●Male sex
●Cigarette smoking
●Positive family history of AAA
●Other large artery aneurysms (eg, iliac, femoral, popliteal)
●Atherosclerosis
●Hypertension
PATHOGENESIS AND NATURAL HISTORY — Aneurysmal degeneration of the abdominal aorta is a multifactorial, systemic process generally felt to be due to alterations in vascular wall biology leading to a loss of vascular structural proteins and wall strength. A common systemic etiology for large vessel (eg, aorta, femoral, iliac, popliteal) aneurysm formation is supported by the occurrence of multiple aneurysms in the same patient. Etiologic factors felt to be important in the development and progression of abdominal aortic aneurysm (AAA) include proteases, inflammatory mediators, and genetic factors. Biomechanical forces, including stresses across the arterial wall, are also felt to play a role. (See "Epidemiology, risk factors, pathogenesis, and natural history of abdominal aortic aneurysm", section on 'Pathophysiology of AAA'.)
An understanding of the management of patients with an AAA requires knowledge of the natural history of this disorder. The natural history of AAA is one of progressive expansion, the rate of which is variable. AAAs expand, on average, at a rate of 0.3 to 0.4 cm per year [24-28]. Expansion tends to be more rapid in smokers and less rapid in patients with diabetes mellitus or peripheral artery disease [26]. Some aneurysms, for unclear reasons, remain relatively fixed in size for a period of time but then undergo rapid expansion. (See "Epidemiology, risk factors, pathogenesis, and natural history of abdominal aortic aneurysm", section on 'Expansion and rupture of AAA'.)
The likelihood that an aneurysm will rupture is increased for those with aneurysm diameter >5.5 cm, a faster rate of expansion (>0.5 cm over a six-month period), those who continue to smoke, and in females. In addition to these, other factors that increase the risk of rupture include recent surgery; medical factors such as uncontrolled hypertension, which may increase aortic wall stress; and, possibly, aneurysm contour [29].
SCREENING — Screening studies show that abdominal aortic aneurysm (AAA) occurs in up to 7 percent of individuals over the age of 50 [18,19,30,31]. However, the majority of AAAs identified at screening are small, and up to 50 percent of those ≤3.5 cm in diameter remain stable throughout follow-up (ie, do not enlarge significantly to warrant treatment) [32]. The effectiveness of population-based screening for AAAs with abdominal ultrasonography has been evaluated in large randomized trials and systematic reviews [33-40]. Screening for AAA in males over age 65 results in a decreased risk of AAA-related mortality; however, for people with a low risk for AAA, any absolute benefit on overall mortality is likely to be small.
We screen males ages 65 to 75 who have ever smoked and suggest screening males aged 65 to 75 who have a first-degree relative who has been diagnosed with AAA. We offer screening to females who have a first-degree relative who has been diagnosed with AAA; screening is not otherwise indicated for females. The Society for Vascular Surgery (SVS) and European Society for Vascular Surgery (ESVS) guidelines also suggest rescreening individuals at the 10-year time point if their original aortic diameter is between 2.5 and 3.0 cm [2]. (See "Screening for abdominal aortic aneurysm".)
CLINICAL PRESENTATIONS — Patients with intact abdominal aortic aneurysm (AAA) may present with or without symptoms.
●Asymptomatic – The majority of patients are asymptomatic. A previously unknown AAA may also become apparent as a result of screening or be discovered incidentally on routine physical examination, on imaging studies performed for other indications, or in the course of evaluating other unrelated conditions. Asymptomatic AAAs are difficult to exclude based on physical examination alone in most patients, even when attempted by experienced examiners [41]. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Asymptomatic AAA'.)
●Symptomatic but not ruptured – Symptomatic AAA refers to any of a number of symptoms that can be attributed to the aneurysm. The development of symptoms may be a sign that AAA configuration is rapidly expanding, has become large enough to compress surrounding structures, or is an inflammatory or infectious aneurysm. Patients with symptomatic AAA most commonly present with abdominal, back, or flank pain, which may or may not be associated with AAA rupture. AAA can also present with other clinical manifestations, such as limb ischemia (acute or chronic), or other systemic manifestations (fever, malaise). In patients with abdominal pain, rupture of the aneurysm must be excluded. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Symptomatic (nonruptured) AAA'.)
●Symptomatic and ruptured – The clinical presentation of ruptured abdominal aortic aneurysm is variable with respect to symptoms and time course. The patient may or may not be aware of the diagnosis of AAA prior to their clinical manifestations of rupture. Only 20 to 30 percent of patients who present to an emergency department with rupture have a known history of AAA [42,43]. The classic presentation of severe pain, hypotension, and a pulsatile abdominal mass occurs in approximately 50 percent of patients [44]. Although the signs and symptoms of ruptured AAA may be obvious, some presentations make ruptured AAA difficult to recognize. Patients with rupture into the retroperitoneum may attribute their symptoms to other causes and delay seeking medical attention. Even after presenting to a physician, a misdiagnosis of ruptured AAA as renal colic, perforated viscus, diverticulitis, gastrointestinal hemorrhage, and ischemic bowel occurs approximately 30 percent of the time [45]. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Ruptured AAA'.)
DIAGNOSIS — A diagnosis of abdominal aortic aneurysm (AAA) is established with imaging studies that demonstrate the aneurysm in the patient suspected of having AAA on the basis of risk factors or on physical examination. Physical examination can reliably diagnose a large AAA (>5.5 cm), but the diagnosis is made using abdominal palpation in fewer than 50 percent of those with AAA. The physical examination should include a complete peripheral arterial vascular examination to assess for signs of thromboembolism or other peripheral aneurysms. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Physical examination'.)
Laboratory studies are not routinely obtained as part of the evaluation of asymptomatic AAA. However, a white blood cell count, blood cultures, and erythrocyte sedimentation rate should be performed in patients with systemic symptoms (eg, fever, weight loss) to evaluate for an infectious cause of AAA or inflammatory aneurysm. For patients with ruptured AAA, routine laboratory studies, and type and crossmatch are obtained.
Imaging — AAA that is suspected based upon clinical symptoms or signs, or incidentally on nonvascular imaging studies (eg, spine magnetic resonance [MR] imaging), should be confirmed with definitive vascular imaging (algorithm 1). For asymptomatic AAA, the imaging test of choice is abdominal ultrasonography, which has sensitivity and specificity approaching 100 percent for an aortic diameter >3.0 cm [46]. Abdominal ultrasound is noninvasive and is ideal for serial imaging in patients with small- and medium-sized aneurysms who are being conservatively managed. However, ultrasound is technician dependent and has other limitations. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Imaging asymptomatic patients' and "Management of asymptomatic abdominal aortic aneurysm", section on 'Aneurysm imaging'.)
Computed tomography (CT) is the imaging test of choice for symptomatic AAA. Contrast-enhanced CT aortography is generally not needed to establish a diagnosis of ruptured AAA [47] but may be essential for planning surgical repair. In patients with symptoms of more than one hour, findings of rupture on CT scan are usually obvious (eg, retroperitoneal hematoma, extravasation of contrast) (image 1) [48]. Other findings on abdominal CT may be associated with unstable aneurysms or "impending rupture" (eg, crescent sign, breaks in aortic wall calcification, aortic blebs) [49-52]. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Imaging symptomatic patients'.)
CT of the abdomen (and MR imaging) can also be used to diagnose and monitor asymptomatic AAA. However, these are generally limited to preoperative planning and to postoperative follow-up of aortic graft repairs. (See "Endovascular repair of abdominal aortic aneurysm", section on 'Endograft surveillance' and "Open surgical repair of abdominal aortic aneurysm", section on 'Follow-up'.)
MANAGEMENT — Abdominal aortic aneurysms (AAAs) are managed according to their diameter and the presence or absence of symptoms. Under most circumstances, patients with symptoms that cannot be definitively attributed to another etiology should be admitted for observation and further vascular evaluation. Asymptomatic aneurysms are evaluated on an outpatient basis, unless they are very large. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Introduction'.)
Ruptured AAA — Repair of ruptured abdominal aortic aneurysm (rAAA) can be offered to most patients, and the timing of the initial evaluation and management of the patient is guided by the hemodynamic status of the patient. (See "Management of symptomatic (non-ruptured) and ruptured abdominal aortic aneurysm", section on 'Ruptured AAA'.)
●Hemodynamically unstable – The hemodynamically unstable patient (persistent in spite of resuscitation) with known AAA who presents with classic symptoms/signs of rupture (hypotension, flank/back pain, pulsatile mass) should be taken emergently to the operating room for immediate control of hemorrhage, resuscitation, and repair of the aneurysm. Imaging confirmation of the presence of AAA in hemodynamically unstable patients suspected but not known to have the disease is ideal prior to intervention but is not required. Preoperative management of hemodynamically unstable patients, including the concept of "hypotensive hemostasis," is an area of active investigation. However, in most circumstances, volume resuscitation should be provided to the least amount necessary to maintain mentation and stabilize blood pressure and pulse rate.
●Hemodynamically stable – For patients with suspected ruptured AAA who are hemodynamically stable, abdominal imaging (preferably computed tomographic [CT] aortography) should be performed urgently to confirm the rupture prior to repair, rule out other potential etiologies as a cause of abdominal pain and hypotension, and determine if an endovascular repair is feasible.
Open surgical versus endovascular repair of ruptured aneurysm — Both open and endovascular techniques can be successfully employed in the treatment of ruptured AAA. Endovascular repair of ruptured AAA may have some advantages over open repair; however, it is not universally available, and the selection of technique is best determined by the available surgical team. Open surgical or endovascular repair of ruptured AAA is accomplished in a manner that is similar to elective repair, with modifications for aortic hemorrhage control, and anticoagulation. Conversion rates from endovascular to open repair for rAAA may be higher compared with elective repair because of unanticipated anatomic features or device-related issues. (See "Surgical and endovascular repair of ruptured abdominal aortic aneurysm".)
Symptomatic (nonruptured) AAA — Aneurysm repair is indicated for patients with symptoms (abdominal/back/flank pain, thromboembolism) that cannot unequivocally be attributed to another etiology, regardless of aneurysm diameter. For patients with symptomatic AAA, the first priority is to determine whether there is any immediate concern that the aneurysm has ruptured or is at high risk for impending rupture, which may be suggested by clinical symptoms or signs, or certain radiologic features (eg, broken calcification, asymmetry) that may indicate instability of the aneurysm. (See "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Imaging symptomatic patients'.)
In the absence of overt rupture, patients with AAA who are thought to be symptomatic or who have possible signs of impending rupture should be admitted for observation and further evaluation. If the patient is a candidate, repair should be accomplished during the same hospitalization. (See "Management of symptomatic (non-ruptured) and ruptured abdominal aortic aneurysm", section on 'Emergency versus delayed repair of symptomatic aneurysm'.)
If the patient is a candidate for repair, a determination needs to be made about whether an open surgical or endovascular approach is more appropriate, primarily based upon an anatomic assessment of aortoiliac anatomy. (See "Endovascular repair of abdominal aortic aneurysm" and "Open surgical repair of abdominal aortic aneurysm".)
Asymptomatic aneurysm — The management of asymptomatic AAA is based upon an assessment of the patient's risk for rupture, compared with the expected risk of perioperative morbidity and mortality associated with repair [53]. When the risk of rupture exceeds the risk of repair, repair is recommended. Conversely, if the risk of repair is greater than the risk of rupture, conservative management and surveillance is recommended. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Aneurysm repair versus conservative management'.)
The assessment of rupture risk depends primarily upon the diameter of the aneurysm at diagnosis and the patient's medical comorbidities. The annual risk of rupture has been found in randomized trials (discussed below) to be similar to, or lower than, the risk of repair in patients with small- or medium-sized aneurysms (<5.5 cm in diameter) [25,54-57]. This diameter threshold for AAA repair is not absolute and may depend on the patient's stature and location of the aneurysm.
Other factors that need to be accounted for include the patient's age and sex, faster expansion rates, and the presence of other peripheral aneurysms. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Other considerations' and "Management of asymptomatic abdominal aortic aneurysm", section on 'Summary of indications for elective AAA repair'.)
Patients who are not candidates for repair or refuse repair should create an advanced directive detailing their wishes in the event of rupture. Family members or other caregivers should be made aware of these wishes, given that the patient may not be able to report these wishes at the time of aneurysm rupture. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Counseling the high-risk patient'.)
Medical therapies — During the period of observation (watchful waiting), medical therapies are aimed at reducing the rate of aortic expansion and morbidity and mortality from cardiovascular disease. However, no medical therapy other than smoking cessation has proven effective at reducing the rate of AAA enlargement and possibly, by extrapolation, risk for rupture. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Therapies to limit aortic expansion'.)
Aneurysm surveillance — During the period of observation, ultrasound surveillance is routinely performed on a schedule that depends primarily upon the diameter of the aneurysm. We generally obtain annual ultrasound; however, a more frequent interval (eg, every six months) may be used depending upon other characteristics of the aneurysm or patient-related factors. Factors that influence the aneurysm surveillance interval are discussed separately. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Aneurysm imaging'.)
AAA REPAIR — Aneurysm repair can be accomplished using open surgical or endovascular techniques. Endovascular aneurysm repair is associated with a lower risk of perioperative morbidity compared with open repair for asymptomatic, symptomatic, and ruptured abdominal aortic aneurysm (AAA). Long-term mortality following elective AAA repair is not significantly different between the techniques. Guidelines from major medical and surgical societies recommend an individualized approach to the patient when choosing between open and endovascular repair, taking into account the patient's age, risk factors for perioperative morbidity and mortality, anatomic factors, and experience of the surgeon [4,5,58]. Given the need for lifelong surveillance with endovascular repair, younger patients with low operative risk may benefit more from open surgical repair, whereas older patients and those with high operative risk may benefit more from endovascular repair, provided their aortoiliac anatomy is appropriate. (See "Management of asymptomatic abdominal aortic aneurysm", section on 'Open versus endovascular aneurysm repair' and "Surgical and endovascular repair of ruptured abdominal aortic aneurysm", section on 'Open surgical versus endovascular repair'.)
Open surgical repair — Open aneurysm repair involves replacement of the diseased aortic segment with a tube or bifurcated prosthetic graft (figure 6) through a midline abdominal or retroperitoneal incision [59]. With technical refinements for open AAA repair, complications such as acute renal failure, distal embolization, wound infection, colonic ischemia, false aneurysm formation, aortoduodenal fistula, graft infection, and perioperative bleeding have become less common following routine elective surgery but remain significant issues following emergent open AAA repair. (See "Open surgical repair of abdominal aortic aneurysm".)
Endovascular repair — Endovascular aneurysm repair (EVAR) involves the placement of modular graft components delivered via the iliac or femoral arteries to line the aorta (figure 6) and exclude the aneurysm sac from the circulation. EVAR requires fulfillment of specific anatomic criteria. With contemporary techniques, including custom-made fenestrated and branched devices, most patients can be considered candidates for EVAR in experienced endovascular centers. (See "Endovascular repair of abdominal aortic aneurysm".)
Some anatomic features of the aorta or iliac arteries may preclude the ability to place an aortic endograft. Endovascular repair may not be anatomically feasible if the aortic neck is occupied by thrombus, there is circumferential calcification at the level of the aortic neck, or both iliac arteries are too small for the intended device. Endovascular repair of juxtarenal or suprarenal aortic aneurysm is not possible where advanced devices and technical expertise are not available. (See "Endovascular repair of abdominal aortic aneurysm", section on 'Anatomic suitability'.)
Endografts — Multiple endovascular devices are commercially available for repair of AAA. Currently available endovascular grafts for infrarenal aortic repair share a bifurcated, modular design. Endografts are chosen to meet size criteria dictated by the size and configuration of the aneurysm. The anatomic measurements of interest include proximal neck length, aneurysm diameter, aortic neck angulation, iliac artery diameter, femoral artery diameter, and aortic length. Other considerations include whether there is flow in the inferior mesenteric artery and the location and number of accessory renal arteries. (See "Endovascular devices for abdominal aortic repair".)
Complications of endograft repair — Complications following endograft placement include systemic complications (eg, myocardial infarction, contrast-induced nephropathy, end-organ ischemia) and complications related to the endograft, such as vascular injury (eg, iliac, femoral), early and late endoleaks, device migration, component separation, stent fracture, limb thrombosis, and endograft infection. (See "Complications of endovascular abdominal aortic repair".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Aortic and other peripheral aneurysms".)
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.)
●Beyond the Basics topics (see "Patient education: Abdominal aortic aneurysm (Beyond the Basics)").
SUMMARY AND RECOMMENDATIONS
●Abdominal aortic aneurysm – For most adults, an aortic diameter >3.0 cm is generally considered aneurysmal. The most important risk factors for the development of abdominal aortic aneurysm (AAA) include older age, male sex, cigarette smoking, positive family history, and the presence of other large artery aneurysms. (See 'Definitions and aortoiliac anatomy' above and 'Epidemiology' above and 'Risk factors' above and 'Pathogenesis and natural history' above.)
●Diagnosis – A definitive diagnosis requires abdominal imaging studies that demonstrate a focal, aortic dilation meeting the criteria for aneurysm (>1.5 times normal diameter, or >3.0 cm in the infrarenal segment). Abdominal ultrasound and computed tomography of the abdomen are both highly sensitive and specific for diagnosing AAA but are recommended under differing clinical circumstances (algorithm 1) depending upon the presence of symptoms and the hemodynamic status of the patient. (See 'Diagnosis' above and "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Summary and recommendations'.)
●Screening for AAA – We screen males ages 65 to 75 who have ever smoked and suggest screening males aged 65 to 75 who have a first-degree relative who has been diagnosed with AAA. We offer screening to females who have a first-degree relative who has been diagnosed with AAA; screening is not otherwise indicated for females. For those in whom an aortic diameter between 2.5 and 3.0 cm was identified, society guidelines also suggest rescreening individuals at 10 years. Screening for other subsets should be individualized. (See 'Screening' above and "Screening for abdominal aortic aneurysm".)
●Clinical presentations – AAA does not typically cause symptoms unless the aneurysm is expanding rapidly, has become large enough to compress surrounding structures, is associated with inflammation (inflammatory aneurysm, infected aneurysm), or has ruptured. Patients with symptomatic AAA most commonly present with abdominal, back, or flank pain. The classic presentation of severe pain, hypotension, and a pulsatile abdominal mass occurs in approximately 50 percent of patients with ruptured AAA. AAA can also present with other clinical manifestations such as limb ischemia (acute or chronic), or systemic manifestations, such as fever or malaise, that may indicate an inflammatory or infectious aneurysm. (See 'Clinical presentations' above and "Clinical features and diagnosis of abdominal aortic aneurysm", section on 'Clinical features'.)
●Management – AAAs are managed according the presence or absence of symptoms. (See 'Management' above and "Management of asymptomatic abdominal aortic aneurysm", section on 'Summary and recommendations' and "Management of symptomatic (non-ruptured) and ruptured abdominal aortic aneurysm", section on 'Summary and recommendations'.)
•Symptomatic AAA
-When ruptured AAA is identified, repair should be undertaken emergently to give the patient the best chance for survival.
-For patients with symptomatic (nonruptured) AAA of any size or configuration who do not have a prohibitive risk for repair, we suggest urgent AAA repair (open or endovascular).
•Asymptomatic AAA
-For most patients with asymptomatic infrarenal AAA <5.5 cm, we recommend conservative management (watchful waiting) rather than elective AAA repair. The risk of aneurysm rupture does not exceed the risk of repair until the aneurysm diameter reaches 5.5 cm. Other factors taken into consideration include the patient's age and sex, expansion rate, and the presence of other peripheral aneurysms. For patients under observation, we generally obtain annual ultrasound; however, a more frequent interval (eg, every six months) may be used depending upon the characteristics of the aneurysm, or other factors. (See 'Asymptomatic aneurysm' above and "Management of asymptomatic abdominal aortic aneurysm", section on 'Aneurysm repair versus conservative management' and "Management of asymptomatic abdominal aortic aneurysm", section on 'Aneurysm imaging'.)
-For good-risk surgical candidates with AAA >5.5 cm, we recommend elective AAA repair (open or endovascular). Situations in which elective repair of AAA <5.5 cm may be appropriate include rapid aortic expansion, coexisting peripheral aneurysm or peripheral artery disease, and female sex. (See 'Asymptomatic aneurysm' above and "Management of asymptomatic abdominal aortic aneurysm", section on 'Summary of indications for elective AAA repair'.)
-For patients with AAA >5.5 cm who have a short life expectancy (<2 years) due to advanced comorbidities, particularly cardiopulmonary disease or malignancy, we suggest no repair over endovascular aneurysm repair. (See 'Asymptomatic aneurysm' above and "Management of asymptomatic abdominal aortic aneurysm", section on 'Counseling the high-risk patient'.)
●Repair techniques – Aneurysm repair can be accomplished using open surgical or endovascular techniques. The choice between open and endovascular AAA repair should be individualized, taking into account the patient's age, risk factors for perioperative morbidity and mortality, anatomic factors, and the experience of the surgeon. Endovascular aneurysm repair is associated with a lower risk of perioperative morbidity compared with open repair for asymptomatic, symptomatic, and ruptured AAA. Long-term mortality following elective AAA repair is not significantly different between the techniques. (See 'AAA repair' above and "Management of symptomatic (non-ruptured) and ruptured abdominal aortic aneurysm", section on 'Summary and recommendations' and "Management of asymptomatic abdominal aortic aneurysm", section on 'Summary and recommendations'.)
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