Abdominal Aortic Aneurysm

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 ^c5
• 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 ^c6
    • As many as 65% of patients with rupture die of sudden cardiovascular collapse before reaching the hospital ^r13c7
  • 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 ^c8
    • Cyanosis and skin mottling coincide with decreased perfusion ^c9c10
    • Femoral and popliteal pulses may be asymmetric or absent ^c11c12c13c14

Physical examination

• Most aneurysms are small, asymptomatic, and detected as incidental findings via ultrasonography or CT scan ^r6c15
• Approximately 30% of asymptomatic aneurysms are detected by a health care provider during routine physical examination ^r6
  • Abdominal bruit may be present ^c16
  • Abdominal midline pulsatile mass may be palpable ^c17
    • Sensitivity of this sign decreases with increasing BMI
  • Prominent popliteal pulses may be present ^c18
    • 15% of patients have coexisting popliteal aneurysm ^c19
• 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

• Cause is uncertain and may be multifactorial
  • Arterial wall inflammation with collagen matrix protein degradation ^c33
  • Atherosclerosis may play a role or may result from arterial wall degradation ^c34
  • Family history
    • Approximately 20% of first-degree relatives of a patient with an abdominal aortic aneurysm develop one as well ^r7c35
    • Aneurysms tend to rupture at smaller diameters in patients with family history of disease ^c36
  • 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 ^c37

Risk factors and/or associations

Other risk factors/associations

• Obesity is an independent risk factor for the presence of abdominal aortic aneurysm ^r3c50
• Atherosclerotic occlusive disease ^r1c51
• Sedentary lifestyle is a risk factor for progression ^c52
• Infection with Chlamydia pneumoniae
  • Small epidemiologic studies suggest possible role of Chlamydia pneumoniae in pathogenesis of abdominal aortic aneurysm with positive serum polymerase chain reaction and immunofluorescence serology results and presence of abdominal aortic aneurysm ^r17c53
• Patients with diabetes have slower abdominal aortic aneurysm growth rate than patients without diabetes, which may be related to metformin treatment ^r18

Primary diagnostic tools

• Physical examination ^c54
  • 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 ^r6c55
  • Aneurysms larger than 5 cm are palpable 76% of the time ^r19c56
  • Ruptured or unstable aneurysms present with abdominal or back pain and hemodynamic instability regardless of size ^c57
• Abdominal imaging
  • Ultrasonography is the imaging modality of first choice for diagnosis and as part of a screening program ^r6r7r18
    • Most widely studied and used imaging tool for evaluating abdominal aortic aneurysm ^r20c58
    • 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 does 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 ^r20c59
  • Abdominal CT angiography
    • Recommended imaging modality for diagnosis of rupture ^r7r18c60
    • 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 ^c61
    • 95% sensitivity and 100% specificity for detecting abdominal aortic aneurysm in asymptomatic patients^r21
    • Does not require contrast medium or radiation
    • Imaging may be suboptimal in patients with obesity
    • 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 ^c62
    • 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 ^c63
    • 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

Most common ^r14

• Mesenteric ischemia ^c64d1
  • Thromboembolic interruption of arterial flow causing intestinal hypoperfusion
    • Patient complains of abdominal pain out of proportion to signs and symptoms
      • Arterial thrombosis ^c65
        • Pain onset is gradual (progressively worsening) with postprandial exacerbation of pain
      • Arterial embolism ^c66
        • Pain onset is acute, severe, and unrelenting
  • Differentiated by CT angiography
• Ureteral calculus ^c67d2
  • 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 shows hydronephrosis in the case of obstructing renal calculus but does not rule out unstable/dissecting abdominal aortic aneurysm
• Diverticulitis ^c68d3
  • 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 ^c69d4
  • 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 ^c70c71d6
  • 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

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

Recommendations for specialist referral

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

Drug therapy

• Statins ^r39
  • 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 ^c73
    • Atorvastatin Calcium Oral tablet; Adults: 80 mg PO once daily. May decrease dose to 40 mg PO once daily if unable to tolerate the higher dose.
  • Rosuvastatin ^c74
    • Rosuvastatin Calcium Oral tablet; Adults: 20 or 40 mg PO once daily.

Nondrug and supportive care

Smoking cessation ^r2

• Can reduce risk of abdominal aortic aneurysm formation and progression ^c75
• Evidence-based strategies include nicotine replacement products, pharmacotherapy (eg, bupropion, varenicline), and counseling ^{c76c77c78c79c80}
  • High-quality evidence indicates that a combination of pharmacotherapy and high-intensity behavioral treatment is more effective than high-intensity behavioral treatment alone ^r40
  • Some evidence indicates that high-intensity behavioral treatment is more effective than low-intensity or usual care ^r40
• 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 ^r41
• Withdrawal agents may also be used instead of nicotine replacement therapy when it is contraindicated; varenicline and sustained-release bupropion are first line choices ^r41

• 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 May 3, 2023. https://www.ahrq.gov/professionals/clinicians-providers/guidelines-recommendations/tobacco/index.html

  Pharmacotherapy	Odds ratio of success
  Combination nicotine patch (longer than 14 weeks) plus ad lib nicotine gum or spray	3.6
  Varenicline 2 mg/day	3.1
  Nicotine patch plus bupropion sustained-release	2.5
  Nicotine patch plus nortriptyline	2.3
  Nicotine nasal spray	2.3
  High-dose (greater than 25 mg) nicotine patch	2.3
  Nicotine gum	2.2
  Nicotine patch plus inhaler	2.2
  Varenicline 1 mg/day	2.1
  Nicotine inhaler	2.1
  Bupropion sustained-release	2
  Nicotine patch plus second-generation antidepressant (paroxetine, venlafaxine)	2
  Regular dose nicotine patch used for either 6-14 weeks or for longer than 14 weeks	1.9

Aerobic exercise ^c81

• Prolonged sedentary lifestyle may promote abdominal aortic aneurysm progression^r42c82c83

Comorbidities

• Other cardiovascular diseases ^c88
  • In patients with abdominal aortic aneurysm between 4 and 5.5 cm in diameter, only 16% of deaths^r44 were due to rupture or repair, whereas over 50% were caused by other cardiovascular diseases (mostly myocardial infarction and stroke) ^c89c90
    • Hypertension coexists frequently in patients with abdominal aortic aneurysm ^c91
      • 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 (eg, myocardial infarction)
    • Atherosclerosis frequently coexists with abdominal aortic aneurysm ^c92
      • Cause-and-effect relationship is firmly established
      • Management is indicated to minimize risk of rupture and occurrence of other cardiovascular events (eg, myocardial infarction, cerebrovascular accident)
• Lower extremity aneurysm ^c93
  • 15% of patients have popliteal aneurysm ^r45c94
  • Test for popliteal aneurysm using ultrasonography if physical examination finds prominent popliteal pulse
• Mycotic aneurysm ^c95
  • Bacterial infection of aneurysm
  • Exceedingly poor prognosis with or without surgical repair ^r46
• Aortoenteric fistula ^c96
  • 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 ^r47

At-risk populations

• Screening recommendations vary between organizations
• US Preventive Services Task Force recommends performing sonography 1 time to screen males aged 65 to 75 years with history of tobacco use ^r12c109
  • Clear linear dose-response relationship exists 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 males aged 65 to 75 years who have never smoked rather than routinely screening all males in this group ^r12c110
  • 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 females 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 females aged 65 to 75 years who have ever smoked or have a family history of abdominal aortic aneurysm ^r12c111
• Canadian Task Force on Preventive Health Care recommends performing 1-time sonography to screen all males aged 65 to 80 years regardless of tobacco use history, owing to data showing reduced abdominal aortic aneurysm–related mortality and rupture ^r51c112
• Canadian Task Force on Preventive Health Care recommends against screening females, regardless of smoking history ^r51
• Society for Vascular Surgery recommends: ^r7
  • 1-time ultrasonographic screening for abdominal aortic aneurysms in males or females aged 65 to 75 years with history of tobacco use ^r7c113
  • 1-time ultrasonographic screening for abdominal aortic aneurysms in males or females older than 75 years with history of tobacco use and in otherwise good health who have not previously received a screening ultrasonographic examination ^r7c114
  • 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 ^r7c115
• American Institute of Ultrasound in Medicine recommends ultrasound screening evaluation for: ^r48
  • Males aged 65 years or older who have ever smoked ^r48
  • Females aged 65 years or older with cardiovascular risk factors ^r48
  • Individuals aged 50 years or older with a family history of aortic and/or peripheral vascular aneurysmal disease ^r48
  • Individuals with a personal history of peripheral vascular aneurysmal disease ^r48
  • Individuals with other risk factors for an abdominal aortic aneurysm ^r48
• Canadian Society for Vascular Surgery: ^r52
  • Recommends 1-time screening ultrasonography for all males aged 65 to 80 years ^r52
  • Suggests 1-time screening ultrasonography for all females aged 65 to 80 years with a history of smoking or cardiovascular disease ^r52
  • Suggests consideration of screening on an individual basis in males and females older than 80 years, based on life expectancy and patient choice ^r52
  • Suggests 1-time screening ultrasonography in those aged 55 years or older for all first-degree relatives of patients with abdominal aortic aneurysm ^r52
  • 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 ^r52

Screening tests

• Ultrasonography is sensitive and specific for detection of stable abdominal aortic aneurysm ^c116