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    Abdominal Aortic Aneurysm

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    Jun.29.2022

    Abdominal Aortic Aneurysm

    Synopsis

    Key Points

    • Abdominal aortic aneurysm is focal dilation (diameter greater than 3 cm) of the abdominal aortic artery involving all layers of the wall
    • Modifiable risk factors include smoking, hypertension, elevated cholesterol level, obesity, and preexisting atherosclerotic occlusive disease r1r2r3
    • Upon rupture, estimated mortality is greater than 80% r4
    • Overall survival rate of patients with surgically repaired abdominal aortic aneurysms is comparable to that of age-matched cohorts
    • Screening and early detection is paramount in reducing rates of mortality associated with rupture
      • Many abdominal aortic aneurysms are asymptomatic until they become unstable and rupture
    • Serial surveillance by ultrasonography is necessary to evaluate for aneurysm enlargement
    • Symptoms of instability and rupture can progress rapidly or gradually, depending on whether weakness in wall extends anteriorly into the abdominal cavity (rapidly fatal) or dissects posteriorly into the retroperitoneum (slower)
    • Surgical or endovascular aneurysm repair is indicated in patients with aneurysm diameters greater than 5.5 cm for men and 5 cm for women who are expected to have long-term benefit from intervention r5

    Urgent Action

    • There must be no delay in admitting patients for emergent operative repair when symptoms associated with impending rupture occur

    Pitfalls

    • Cannot rely on clinical examination to exclude abdominal aortic aneurysm r6
      • Patients with abdominal aortic aneurysm risk factors who present with abdominal, flank, or back pain must have ultrasonographic imaging to eliminate unstable abdominal aortic aneurysm as source of symptoms
        • If ultrasonogram shows abdominal aortic aneurysm, CT angiography is necessary to eliminate dissection as the cause of the symptoms
    • Avoid delay in referral of symptomatic patients to emergent vascular surgery evaluation r7

    Terminology

    Clinical Clarification

    • Abdominal aortic aneurysm is focal dilation (diameter greater than 3 cm) of the abdominal aortic artery involving all layers of the wall

    Classification

    • By location
    • By size and rupture risk
      • Precise risk modeling is multivariate,r8r9 but size provides a useful clinical guide
      • Data from various studies support estimates as follows: r10
        • Small (3-3.9 cm)
          • No risk of rupture
        • Medium (4-4.9 cm)
          • Rupture risk is 1% per year
        • Large (5-5.9 cm)
          • Rupture risk is 5% to 10% per year
        • Very large (6-6.9 cm)
          • Rupture risk is 10% to 20% per year
        • Giant (7-7.9 cm)
          • Rupture risk is 20% to 40% per year
        • Greater than 8 cm
          • Rupture risk is 30% to 50% per year
    • By shape
      • Factors into decisions regarding timing and approach to operative repair r11
        • Fusiform (true aneurysm)
          • Weakness involves the entire circumference and length of the aorta
        • Saccular (pseudoaneurysm)
          • Weakness is a blister or bleb of the aorta that does not involve the entire circumference

    Diagnosis

    Clinical Presentation

    History

    • Presence and severity of symptoms depend on size and stability of aneurysm
      • Approximately 90% of aneurysms identified by screening are 5.5 cm or smaller r12
    • Aneurysms 3.9 cm or smaller may be totally asymptomatic r6c1
    • Symptoms generally start when aneurysm is 4 cm or larger; symptoms include:
      • Early satiety c2
      • Nausea/vomiting c3c4
      • Urinary symptoms of bladder compression and irritation c5c6
    • As aneurysm becomes large and unstable, symptoms become more prominent
      • Symptoms depend on whether aneurysm is weakening anteriorly or dissecting posteriorly into retroperitoneum
        • Syncope may be first symptom of unstable or rupturing aneurysm c7
        • As many as 65% of patients with rupture die of sudden cardiovascular collapse before reaching the hospital r13c8
      • Data regarding incidence are difficult to verify, but additional complications of aneurysmal leakage and instability include intraperitoneal hemorrhage and decreased perfusion to lower extremities
        • Turner sign (flank ecchymosis) represents retroperitoneal hemorrhage c9
        • Cyanosis and skin mottling coincide with decreased perfusion c10c11
        • Femoral and popliteal pulses may be asymmetrical or absent c12c13c14c15

    Physical examination

    • Most aneurysms are small, asymptomatic, and detected as incidental findings via ultrasonography or CT scan r6c16
    • Approximately 30% of asymptomatic aneurysms are detected by a health care provider during routine physical examination r6
      • Abdominal bruit may be present c17
      • Abdominal midline pulsatile mass may be palpable c18
        • Sensitivity of this sign decreases with increasing BMI
      • Prominent popliteal pulses may be present c19
        • 15% of patients have coexisting popliteal aneurysm
    • As aneurysms become unstable and begin to dissect, evidence of cardiovascular instability develops
      • Blood pressure may remain consistently elevated until late in progression of dissection c20c21
      • Abdominal, flank, back, groin, or scrotal pain c22c23c24c25
      • Ripping sensation in the back c26
      • Lower extremity pain, coolness, paralysis, and paresthesia c27c28c29c30
      • Embolic phenomena resulting in livedo reticularis and painful blue toes c31c32

    Causes and Risk Factors

    Causes

    • Cause is uncertain and may be multifactorial
      • Arterial wall inflammation with collagen matrix protein degradation
      • Atherosclerosis may play a role or may result from arterial wall degradation
      • Family history
        • Approximately 20% of first-degree relatives of a patient with an abdominal aortic aneurysm develop one as well r7c33
        • Aneurysms tend to rupture at smaller diameters in patients with family history of disease c34
      • Smoking is strongly associated with development of abdominal aortic aneurysm r2
        • Smokers are 7.6 times more likely to have an abdominal aortic aneurysm than nonsmokers c35

    Risk factors and/or associations

    Age
    • Incidence rises rapidly after age 60 years in men and 70 years in women c36c37c38c39
    • Affects 8% of men older than 65 years r14
    Sex
    • Men are 6 to 10 times more likely than women to have an abdominal aortic aneurysm r4c40c41
    • Abdominal aortic aneurysms tend to be more aggressive with more rapid expansion and have a higher tendency to rupture at smaller diameters in women
    Genetics
    • Genetic syndromes associated with abdominal aortic aneurysmr4 are as follows:
      • Ehlers-Danlos syndrome r15c42
        • Spectrum of arterial and venous anomalies, including progressive aneurysm formation with spontaneous vascular dissection and rupture
      • Marfan syndrome r16c43
        • Patients with Marfan syndrome are more likely to have thoracic aortic aneurysms but can also develop abdominal aortic aneurysms
        • Those with true abdominal aortic aneurysms tend to be younger and have short life expectancy
    Ethnicity/race
    • More frequent in White populations as compared with Hispanic or African American populations r7c44c45c46c47

    Other risk factors/associations

    • Obesity is an independent risk factor for the presence of abdominal aortic aneurysm r3c48
    • Atherosclerotic occlusive disease r1c49
    • Sedentary lifestyle is a risk factor for progression c50
    • Infection with Chlamydia pneumonia
      • Small epidemiologic studies suggest possible role of Chlamydia pneumonia in pathogenesis of abdominal aortic aneurysm with positive serum polymerase chain reaction and immunofluorescence serology results and presence of abdominal aortic aneurysm r17c51
    • Patients with diabetes have slower abdominal aortic aneurysm growth rate than patients without diabetes, which may be related to metformin treatment r18

    Diagnostic Procedures

    Primary diagnostic tools

    • Physical examination c52
      • Small aneurysms (smaller than 3.9 cm) are usually asymptomatic
      • Careful abdominal examination by an experienced diagnostician can identify a pulsatile abdominal mass in the 3- to 3.9-cm range 29% of the time r6
      • Aneurysms larger than 5 cm are palpable 76% of the time r19
      • Ruptured or unstable aneurysms will present with abdominal or back pain and hemodynamic instability regardless of size
    • Abdominal imaging
      • Ultrasonography is the imaging modality of first choice for diagnosis and as part of a screening program r6r7r18
        • The most widely studied and used imaging tool for evaluating abdominal aortic aneurysm r20
        • Very accurate and sensitive; avoids ionizing radiation
        • Patients with abdominal aortic aneurysm risk factors who present with abdominal, flank, or back pain must have ultrasonographic imaging to eliminate unstable abdominal aortic aneurysm as source of symptoms
      • Abdominal CT scan
        • Accurate and sensitive for diagnosis of abdominal aortic aneurysm but will not reliably diagnose rupture or dissection and requires exposure to radiation
        • Contrast-enhanced CT is well established in the literature and is capable of identifying aortic aneurysms r20
      • Abdominal CT angiography
        • Recommended imaging modality for diagnosis of rupture r7r18
        • Provides important anatomic information to determine whether rupture has occurred and if patient is a candidate for emergency endovascular repair r18
        • If ultrasonogram shows abdominal aortic aneurysm, CT angiography is necessary to eliminate dissection as the cause of the symptoms
        • Relative to ultrasonography, considered slightly more accurate at determining aneurysm diameter r20

    Imaging

    • Abdominal aortic aneurysms are often discovered incidentally by imaging done for other reasons
    • Diagnostic accuracy depends on the size, stage, and stability of the aneurysm
      • Ultrasonography c53
        • 95% sensitivity and 100% specificity for detecting abdominal aortic aneurysm in asymptomatic patientsr21
        • Does not require contrast medium or radiation
        • Imaging may be suboptimal in patients who are obese
        • Focused abdominal sonographic findings in trauma examination will show blood from aneurysmal rupture in dependent areas of the abdomen
          • Indicated for unstable patients to direct to either immediate surgical repair (positive focused abdominal sonographic findings in trauma) or CT angiography (negative or equivocal focused abdominal sonographic findings in trauma)
          • Cannot exclude retroperitoneal aneurysmal dissection
        • In stable patients, not sufficiently precise for procedural planning
      • CT angiography c54
        • Provides better detail and definition of abdominal structures than ultrasonography
          • Useful for poor-quality or indeterminate ultrasonography results
          • Useful pretreatment planning
        • Requires iodinated contrast medium and radiation
        • Features of an impending rupture that can be seen on CT scan include the following: r22
          • Periaortic blood
          • Hemorrhage into a mural thrombus
          • Peripheral crescent-shaped attenuation within the aneurysm
          • Increased size (assuming a comparison study is available)
      • Magnetic resonance angiography c55
        • Higher cost compared to CT angiography and ultrasonography
        • Does not require radiation
        • Contraindicated for patients with metal clips or pacemakers
        • For preintervention studies, may be substituted if CT cannot be performed r23
        • Can be obtained without the use of IV contrast, making it an option for patients with advanced chronic renal disease r20

    Differential Diagnosis

    Most common r14

    • Mesenteric ischemia c56d1
      • Thromboembolic interruption of arterial flow causing intestinal hypoperfusion
        • Patient complains of abdominal pain out of proportion to signs and symptoms
          • Arterial thrombosis c57
            • Pain onset is gradual (progressively worsening) with postprandial exacerbation of pain
          • Arterial embolism c58
            • Pain onset is acute, severe, and unrelenting
      • Differentiated by CT angiography
    • Ureteral calculus c59d2
      • Acute, severe pain in back, flank, or abdomen
        • Cannot differentiate from dissecting retroperitoneal aneurysm on clinical grounds alone
      • Differentiated by CT imaging, preferably without contrast medium on initial phase
        • Ultrasonography will show hydronephrosis in the case of obstructing renal calculus but will not rule out unstable/dissecting abdominal aortic aneurysm
    • Diverticulitis c60d3
      • Pain commonly located in left lower quadrant of abdomen or left flank
        • Typically, slower onset of pain (over 1-3 days) accompanied by low-grade fever and inflammatory peritoneal signs
      • Differentiated by CT imaging with IV and oral contrast medium
    • Pancreatitis c61d4
      • Can produce severe midabdominal pain radiating to central back d5
        • Often accompanied by nausea and vomiting
      • Typically slower onset of epigastric pain (over hours or days)
      • Differentiated by CT imaging with IV contrast medium
    • Peptic ulcer disease/perforated ulcer c62c63d6
      • Can produce severe midabdominal pain radiating to central back
        • Typically slower onset and progression of symptoms (over hours or days)
          • Bloody emesis and bowel movements accompany pain
      • Differentiated by CT imaging with IV contrast medium

    Treatment

    Goals

    • Identify abdominal aortic aneurysm
    • Immediate treatment goals depend on stability of aneurysm
      • Ruptured or dissecting aneurysms require immediate surgical stabilization and repair regardless of size
    • Stable aneurysms less than 4.5 to 5.5 cm in diameter require elective consultation with a vascular surgeon regarding advisability of repair
    • Stable aneurysms less than 5.5 to 6 cm in diameter require urgent consultation with a vascular surgeon regarding advisability of repair
    • Repair aneurysms 6 cm or larger whether they are symptomatic or not
    • Reduce risk factors
      • Encourage weight loss if patient is obese
      • Promote an active lifestyle
      • Advise smoking cessation

    Disposition

    Admission criteria

    Ruptured and dissecting abdominal aortic aneurysm can cause death within seconds or minutes

    • There must be no delay in admitting patients for emergent operative repair when symptoms associated with impending rupture occur

    Symptoms associated with impending rupture or dissection include the following:

    • Shock with unstable vital signs
    • Cold, clammy skin
    • Dizziness
    • Syncope
    • Abdominal pain
    • Pain or decreased pulses in extremities from embolism
    Criteria for ICU admission
    • Postoperative recovery after surgical or endovascular repair
    • If repair of symptomatic abdominal aortic aneurysm is delayed to optimize coexisting medical conditions, monitor patient in an ICU setting, with blood products available r7

    Recommendations for specialist referral

    • Refer patients to vascular surgeon for consultation at time of initial diagnosis with abdominal aortic aneurysm r7

    Treatment Options

    Watchful waiting with medical management r24

    • Observe small aneurysms with diameters up to 5.5 cm in men and 5 cm in women r5
      • Small aneurysms (less than 5.5 cm in men and 5 cm in women) can rupture, and risk of death from treatment-related mortality is less than that from rupture; however, rupture risk is low for small aneurysms without other risk factors
      • A 2020 Cochrane Review reported there was no evidence of an advantage to early repair for small abdominal aortic aneurysm (4-5.5 cm) r25
    • Medical management
      • Smoking cessation is the most important intervention r7d7
      • Use statins, antihypertensive drugs, and antiplatelet drugs for medical management of traditional cardiovascular risk factors; abdominal aortic aneurysm is considered a coronary heart disease equivalent r7r26
        • 5-year survival rate is better in patients receiving these agents compared with rates in patients not receiving each therapy, respectively: r27
          • Statins: 68% versus 42%
          • Antihypertensives: 62% versus 39%
          • Antiplatelet drugs: 62% versus 39%
        • Guidance for use of such therapies and therapeutic targets is provided in recent multidisciplinary clinical practice guidelinesr28r29r30r26
      • Many classes of medication, including statins, β-blockers, ACE inhibitors, angiotensin receptor blockers, and antibiotics have been evaluated for their potential to limit aneurysm progression, but none have been shown in large randomized trials to provide benefit r31
        • Society for Vascular Surgery practice guidelines suggest not administering these drugs for the sole purpose of reducing risk of abdominal aortic aneurysm expansion and rupture r7
    • Surgical/interventional management
      • It is essential to select patients who are expected to have a long-term benefit from elective intervention
      • For most patients in good health, elective surgical or endovascular repair is indicated for aneurysms with diameters larger than 5.5 cm in men and larger than 5 cm in women r5r18
        • The following circumstances reinforce need for repair of smaller-diameter lesions:
          • Symptomatic (most commonly pain in abdomen, back, or flank) r7
            • Symptoms are a harbinger of rupture and require immediate referral and treatment
          • Expansion of diameter greater than 0.5 cm in 6-month period (or larger than 1 cm/year)r18, regardless of absolute size
            • Accelerated expansion is associated with greater risk of rupture than diameter alone
          • Presence of a saccular aneurysm (most are fusiform)
            • Associated with a greater risk of rupture
      • Choice of open versus endovascular surgical repair
        • Decision regarding type of procedure should be individualized—based on age, overall health, anatomic features, and patient preference
          • The Society for Vascular Surgery recommends calculation of perioperative risk score to aid in decision making;r7 the Vascular Quality Initiative (VQI) scoring toolr32 is available online
          • European Vascular Society guidelines recommend endovascular abdominal aortic aneurysm repair for most patients with suitable anatomy and reasonable life expectancy r18
            • Endovascular aneurysm repair has lower 30-day procedural morbidity and mortality but there is no long-term mortality difference between endovascular aneurysm repair and open aneurysm repair r33r34c64
            • For patients with comorbid advanced chronic renal insufficiency and oxygen-dependent chronic obstructive pulmonary disease, endovascular aneurysm repair outcomes are superior to those achieved with contemporary open repair, particularly when it is performed under local or regional anesthesia r7
          • Open surgical repair may be preferred for younger patients with longer life expectancy r18
        • For ruptured abdominal aortic aneurysms, emergency endovascular aneurysm repair and conventional open surgical repair show similar outcomes and mortality rates r35
          • Society for Vascular Surgery practice guidelines recommend endovascular aneurysm repair over open repair for treatment of ruptured abdominal aortic aneurysm r7
      • A 2021 systematic review indicated a beneficial effect of statins on long-term survival in patients after abdominal aortic aneurysm repair r36
    • Additional guidelines have been published by the National Institute for Health Care and Excellence r37

    Drug therapy

    • Statins r38
      • For secondary prevention of atherosclerotic disease, use high-intensity statins for adults aged 75 years or younger (achieves greater than 50% reduction in baseline LDL cholesterol level) r29
      • Atorvastatin c65
        • Atorvastatin Calcium Oral tablet; Adults: 80 mg PO once daily has been shown to reduce the progression of atherosclerosis in clinical trials.
      • Lovastatin c66
        • Lovastatin Oral tablet; Adults: Initially, 20 mg PO once daily with evening meal. Dosage range: 10 to 80 mg/day PO in single doses or divided twice daily. Max: 80 mg/day PO. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.
      • Pravastatin c67
        • Pravastatin Sodium Oral tablet; Adults: 40 to 80 mg PO once daily. Max: 80 mg/day. Assess LDL-C 4 to 12 weeks after initiation or dose adjustment; adjust dosage as needed. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.
      • Simvastatin c68
        • Simvastatin Oral tablet; Adults: Initially, 20 to 40 mg PO once daily in the evening. Usual range: 20 to 40 mg PO once daily in the evening. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions. Chinese patients taking lipid-modifying doses of niacin should receive less than 80 mg/day. Only use 80 mg in patients who have been taking 80 mg chronically without myopathy.

    Nondrug and supportive care

    Smoking cessation r2

    • Can reduce risk of abdominal aortic aneurysm formation and progression c69
    • Evidence-based strategies include nicotine replacement products, pharmacotherapy (eg, bupropion, varenicline), and counseling c70c71c72c73c74
      • High-quality evidence indicates that a combination of pharmacotherapy and high-intensity behavioral treatment is more effective than high-intensity behavioral treatment alone r39
      • Some evidence indicates that high-intensity behavioral treatment is more effective than low-intensity or usual care r39
    • Nicotine replacement therapy may also be supplemented with agents shown to mitigate the effects of withdrawal; a combination of nicotine replacement plus sustained-release bupropion is recommended r40
    • Withdrawal agents may also be used instead of nicotine replacement therapy when it is contraindicated; varenicline and sustained-release bupropion are first line choices r40
    • First line pharmacotherapy to aid in smoking cessation.Data from Agency for Healthcare Research and Quality: Treating Tobacco Use and Dependence: 2008 Update. AHRQ website. Published 2008. Reviewed February 2020. Accessed March 5, 2021. https://www.ahrq.gov/professionals/clinicians-providers/guidelines-recommendations/tobacco/index.html
      PharmacotherapyOdds ratio of success
      Combination nicotine patch (longer than 14 weeks) plus ad lib nicotine gum or spray3.6
      Varenicline 2 mg/day3.1
      Nicotine patch plus bupropion sustained-release2.5
      Nicotine patch plus nortriptyline2.3
      Nicotine nasal spray2.3
      High-dose (greater than 25 mg) nicotine patch2.3
      Nicotine gum2.2
      Nicotine patch plus inhaler2.2
      Varenicline 1 mg/day2.1
      Nicotine inhaler2.1
      Bupropion sustained-release2
      Nicotine patch plus second-generation antidepressant (paroxetine, venlafaxine)2
      Regular dose nicotine patch used for either 6-14 weeks or for longer than 14 weeks1.9

    Aerobic exercise c75

    • Prolonged sedentary lifestyle may promote abdominal aortic aneurysm progressionr41
    Procedures
    Open or laparoscopic surgical repair c76c77
    General explanation
    • Removes dilated section of abdominal aorta and replaces it with synthetic graft material
      • Discharge is typically 4 to 9 days after procedure
      • Normal activity can be resumed in about 4 weeks
    Indication
    • Aneurysm 5.5 cm or larger in men
    • Aneurysm 5 cm or larger in women
    • Symptomatic aneurysm of any size
    Contraindications
    • Uncorrected coagulopathy
    Complications
    • Perioperative mortality is 5% for elective repair r14
    • Ischemic colitis and spinal cord ischemia are common postoperative complications
    Endovascular aneurysm repair c78
    General explanation
    • Aneurysmal section of aorta is not replaced. A stent is placed inside aneurysm via femoral artery cannulation
    • Procedure involves incision into the groin to expose femoral artery
    • A catheter is threaded into aorta under radiographic fluoroscopic guidance
      • A stent graft is placed into the aneurysm and a balloon is inflated to stabilize the aorta
    • Blood flows through graft instead of dilated aorta
    • Typically reserved for infrarenal abdominal aortic aneurysms with sufficient normal aorta above graft to allow for anchoring without occluding renal arteries
    • Evidence suggests that for repair of ruptured abdominal aortic aneurysms, endovascular repair and open surgical repair produce similar outcomes, complication rates, and 30-day mortality rates r35
    • Evidence suggests there is no long-term mortality benefit in comparison with open surgical repair r42
    Indication
    • Aneurysm 5.5 cm or larger in men
    • Aneurysm 5 cm or larger in women
    • Symptomatic aneurysm of any size
    Contraindications
    • Uncorrected coagulopathy
    • Anatomically unfavorable aneurysms

    Complications

    • Grafts occasionally leak into excluded aneurysm sacs, requiring urgent reintervention in some cases
    • Perioperative mortality (1%-2%) is lower than for open repair; however, midterm and long-term data proving an all-cause mortality benefit are lacking
      • Approximately 20% to 30% of patients who undergo endovascular repair require secondary intervention within 6 years
    • Ischemic colitis and spinal cord ischemia are common postoperative complications

    Comorbidities

    • Other cardiovascular diseases c79
      • In patients with abdominal aortic aneurysm between 4 and 5.5 cm in diameter, only 16% of deathsr43 were due to rupture or repair, whereas over 50% were caused by other cardiovascular diseases (mostly myocardial infarction and stroke) c80c81
        • Hypertension coexists frequently in patients with abdominal aortic aneurysm c82
          • Cause-and-effect relationship has not been convincingly established
            • Manage and control hypertension to minimize shearing effect on abdominal aortic aneurysm wall and risk of aneurysm rupture, as well as occurrence of other cardiovascular events, such as myocardial infarction
        • Atherosclerosis frequently coexists with abdominal aortic aneurysm c83
          • Cause-and-effect relationship is firmly established
          • Management is indicated to minimize risk of rupture and occurrence of other cardiovascular events, such as myocardial infarction or cerebrovascular accident
    • Lower extremity aneurysm c84
      • 15% of patients have popliteal aneurysm r44c85
      • Test for popliteal aneurysm using ultrasonography if physical examination finds prominent popliteal pulse
    • Mycotic aneurysm c86
      • Bacterial infection of aneurysm
      • Exceedingly poor prognosis with or without surgical repair r45
    • Aortoenteric fistula c87
      • Almost exclusively secondary to abdominal aortic aneurysm repair
      • Any patient with history of abdominal aortic aneurysm repair presenting with gastrointestinal bleeding requires immediate CT angiography to investigate for aortoenteric fistula r46

    Monitoring

    • Ultrasonographic surveillance
      • Follow abdominal aortic aneurysms with repeated sonography at specified intervals, according to size
        • Greater than 2.5 cm but less than 3 cm r7
          • Repeat sonography after 10 years c88
        • 3 to 3.9 cm r7r47
          • Repeat sonography every 36 months c89
        • 4 to 4.9 cm r7r47
          • Repeat sonography every 12 months c90
        • 5 to 5.4 cm r7r47
          • Repeat sonography every 6 months c91
        • Refer patients with abdominal aortic aneurysms larger than 5.4 cm to a vascular subspecialist for treatment r5c92
      • Follow-up patients after aneurysm repair, particularly endovascular repair r47
    • Non–contrast-enhanced CT of entire aorta is recommended at 5-year intervals after aneurysm repair (either endovascular or open) r7c93
    • Monitor and control blood pressure and fasting serum lipid values r26c94c95

    Complications and Prognosis

    Complications

    • Aneurysm rupture c96
      • Size and expansion rate are greatest predictors of rupture
      • Aneurysm size greater than 8 cm has a 30% to 50% risk of rupture r10
      • Upon rupture, estimated mortality is greater than 80% r4
      • Expansion is more rapid in smokers
    • Arterial embolism c97
      • Cholesterol plaques and thrombotic material embolize off the aneurysmal wall and cause interruption of arterial blood flow distally
    • Hydronephrosis c98
      • From aneurysm compression on ureter (typically left side)
        • Pain is more common in lumbar area
      • Ureter becomes compressed in approximately 20% of aneurysms
    • Aortoenteric fistula c99
      • Communication develops between inflamed aortic aneurysm and portion of intestine
        • Sentinel bleed occurs when blood from aorta enters gastrointestinal tract for a brief period, then stops
          • Period of time between sentinel bleed and exsanguinating gastrointestinal bleed is variable (anywhere from 5 hours to 5 months) r48

    Prognosis

    • Overall survival rate of patients with surgically repaired abdominal aortic aneurysms is comparable to that of age-matched cohorts
    • Cardiovascular and pulmonary disease are leading causes of early and late death after both open surgical and endovascular aneurysm repair r7
    • Nonmodifiable prognostic risk factors associated with poor patient survival after elective repair include end-stage renal disease and chronic obstructive pulmonary disease requiring supplementary oxygen r49
    • Upon rupture, the estimated mortality is greater than 80% r4

    Screening and Prevention

    Screening

    At-risk populations

    • Screening recommendation vary between organizations
    • US Preventive Services Task Force recommends performing sonography 1 time to screen men aged 65 to 75 years with history of tobacco use r12c100
      • There is a clear linear dose-response relationship between development of abdominal aortic aneurysm and duration of smoking r2
        • Each year of smoking increases relative risk of abdominal aortic aneurysm by 4% r2
    • US Preventive Services Task Force recommends selectively offering screening sonography in men aged 65 to 75 years who have never smoked rather than routinely screening all men in this group r12c101
      • Consider the balance of benefits and harms on the basis of evidence relevant to the patient's medical history, family history, other risk factors, and personal values
    • US Preventive Services Task Force recommends against routine screening in women who have never smoked and have no family history of abdominal aortic aneurysm, but concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for abdominal aortic aneurysm with ultrasonography in women aged 65 to 75 years who have ever smoked or have a family history of abdominal aortic aneurysm r12c102
    • Canadian Task Force on Preventive Health Care recommends performing one-time sonography to screen all men aged 65 to 80 years regardless of tobacco use history, owing to data showing reduced abdominal aortic aneurysm–related mortality and rupture r50c103
    • Canadian Task Force on Preventive Health Care recommends against screening women, regardless of smoking history r50
    • Society for Vascular Surgery recommends: r7
      • One-time ultrasonographic screening for abdominal aortic aneurysms in men or women aged 65 to 75 years with history of tobacco use r7c104
      • One-time ultrasonographic screening for abdominal aortic aneurysms in men or women older than 75 years with history of tobacco use and in otherwise good health who have not previously received a screening ultrasonographic examination r7c105
      • Ultrasonographic screening for abdominal aortic aneurysms in first-degree relatives of patients who present with an abdominal aortic aneurysm; perform screening in first-degree relatives who are aged between 65 and 75 years or in those older than 75 years and in good health r7c106
    • The American Institute of Ultrasound in Medicine recommends ultrasound screening evaluation for: r47
      • Men aged 65 years or older who have ever smoked r47
      • Women aged 65 years or older with cardiovascular risk factors r47
      • Individuals aged 50 years or older with a family history of aortic and/or peripheral vascular aneurysmal disease r47
      • Individuals with a personal history of peripheral vascular aneurysmal disease r47
      • Individuals with other risk factors for an abdominal aortic aneurysm r47
    • The Canadian Society for Vascular Surgery: r51
      • Recommends one-time screening ultrasonography for all men aged 65 to 80 years r51
      • Suggests one-time screening ultrasonography for all women aged 65 to 80 years with a history of smoking or cardiovascular disease r51
      • Suggests consideration of screening on an individual basis in men and women older than 80 years, based on life expectancy and patient choice r51
      • Suggests one-time screening ultrasonography in those aged 55 years or older for all first-degree relatives of patients with abdominal aortic aneurysm r51
      • Suggests consideration of repeat ultrasonography 10 years after initial screening for patients with initial aortic diameter larger than 2.5 cm and less than 3 cm, based on life expectancy and patient choice r51

    Screening tests

    • Ultrasonography is sensitive and specific for detection of stable abdominal aortic aneurysm c107

    Prevention

    • Risk-factor modification
      • Avoid smoking c108
      • Avoid high-fat diet c109
      • Participate in aerobic exercise activity for at least 150 minutes every week c110
      • Avoid or treat obesity c111
      • Actively manage blood pressure and cholesterol c112c113
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