Aneurysm of the Abdominal Aorta

Descriptive text is not available for this image BASICS

DESCRIPTION

  • There are two types of aneurysms: true and false. A true aneurysm involves all three vessel wall layers. False aneurysms or pseudoaneurysms occur when the intimal and medial layers are disrupted and the dilated segment is surrounded by the adventitia only. Ruptures are usually higher with false aneurysms due to poor support of the aneurysmal wall.
  • Abdominal aortic aneurysm (AAA) is the most common true arterial aneurysm. False aneurysms of the abdominal aorta are usually due to trauma or infection.
  • The average diameter of the infrarenal aorta is 2 cm; an aortic diameter of ≥3 cm is considered aneurysmal.
  • In men, AAA diameters are predictive of clinical events. In women, aneurysms are still defined as >3 cm, but the aortic scaling index (ASI; diameter [cm] / body surface area [m2]) is more predictive of clinical events.
  • System(s) affected: cardiovascular; neurologic; heme/lymphatic/immunologic
  • Synonym(s): aortic aneurysms; AAA

Geriatric Considerations
Incidence of AAA, risk of rupture, and operative morbidity and mortality all rise with age.Pediatric Considerations
Rare in children; may be associated with umbilical artery catheters, connective tissue diseases, arteritides, or congenital abnormalities

EPIDEMIOLOGY

  • Estimated prevalence of AAA in developed countries is 2–8%. Age-related increase is seen more with men than women.
  • Ultrasound studies show that 4–8% of older men have an occult AAA.
  • 90% of all AAA >4 cm are related to atherosclerotic disease, with the vast majority located infrarenally.
  • Predominant gender: male > female

Incidence

  • Roughly 15,000 deaths per year and the 15th leading cause of death in the United States.
  • 0.4% to 0.67% in Western populations or 2.5 to 6.5 aneurysms per 1,000 patient-years
  • If stratified into years, the incidence of AAA is increased in the older populations. For example, the incidence increases from 55 to 298 per 100,000 patient-years if comparing men aged 65 to 74 years versus men >85 years of age.

Prevalence

  • The prevalence of AAA-associated mortality has decreased by 50% since the 1990s, likely due to the decline in cigarette smoking, increased screening for AAA detection, and early interventions.
  • With the increasing life expectancy in developed countries, the prevalence of AAA is expected to increase, but the decreased prevalence of smoking will have the opposite effect.

ETIOLOGY AND PATHOPHYSIOLOGY

  • AAAs are caused by degradations of abnormal production of elastin and collagen, the structural components of the aortic wall.
  • There are many causes of aortic aneurysms: inflammation, degenerative disorders, vasculitis, infections, and trauma. However, the vast majority of AAA are caused by inflammation with atherosclerosis as the inciting factor.
  • Although most aortic aneurysms are caused by inflammatory or degenerative destruction of elastin and collagen; infections, trauma, and connective tissues disorders can also degrade elastin and collagen, leading to similar presentations.
  • The natural course of an AAA is progressive expansion, based on multiple factors, the most important being ongoing smoking.

Genetics

  • Familial AAA have a variable polygenetic inheritance pattern.
  • Monogenetic inheritance patterns such as: Marfan syndrome (fibrillin-1 defect), Ehlers-Danlos syndrome (type IV collagen defect), or Loeys-Dietz syndrome are more commonly associated with thoracoabdominal aortic aneurysms.

RISK FACTORS

Older age, male sex, Caucasian race, family history, smoking, hypertension (HTN), hyperlipidemia, atherosclerosis, peripheral aneurysms, obesity

GENERAL PREVENTION

  • Address cardiovascular disease risk factors.
  • Follow screening guidelines: U.S. screening for detection of AAA in male patients, aged 65 to 75 years, who have ever smoked.

COMMONLY ASSOCIATED CONDITIONS

  • HTN, myocardial infarction (MI), heart failure, carotid artery atherosclerosis, lower extremity peripheral arterial disease, tobacco abuse
  • Screening for thoracic aneurysm should also be considered.
  • 20% of patients with AAA have concurrent thoracic aneurysm (1).

Descriptive text is not available for this image DIAGNOSIS

  • Asymptomatic AAA (majority)
    • USPSTF recommends a one-time screen for an AAA by abdominal ultrasonography for men aged 65 to 75 years with a smoking history (2)[A].
    • Selective screening for AAAs in nonsmoker men aged 65 to 75 years can be offered based on personal or family history and patient’s preferences (2)[A].
    • Women with a first-degree relative with an AAA can be offered screening via abdominal ultrasonography (1)[C].
ALERT
  • Symptomatic: The triad of shock, pulsatile mass, and abdominal pain always suggest rupture of AAA, and immediate surgical evaluation is recommended (1).
    • Hemodynamically stable patients (shock is absent as the rupture is contained) may undergo a CT abdomen with IV contrast for evaluation of an AAA.
    • Unstable patients (rupture is uncontained) undergo a focused bedside ultrasound and surgical repair if AAA is present.
  • Unusual presentations:
    • Primary aortoenteric fistula: erosion/rupture of AAA into duodenum
    • Aortocaval fistula: erosion/rupture of AAA into vena cava or left renal vein: 3–6%

HISTORY

  • Abdominal, back, or flank pain
  • AAA risk factors, hypotension if presenting in an emergency situation
  • Found on routine screening if presenting in an outpatient setting

PHYSICAL EXAM

  • Pulsatile supraumbilical mass
  • Encroachment by aneurysm
    • Vertebral body erosion, gastric outlet obstruction, ureteral obstruction
    • Lower extremity ischemia secondary to embolization of mural thrombus
  • Rupture leads to tachycardia, hypotension, evidence of shock and anemia, and possible flank contusion (Grey Turner sign).

DIFFERENTIAL DIAGNOSIS

  • Other abdominal masses
  • Other causes of abdominal or back pain (e.g., peptic ulcer disease, renal colic, diverticulitis, appendicitis, incarcerated hernia, bowel obstruction, GI hemorrhage, arthritis, metastatic disease, MI)

DIAGNOSTIC TESTS & INTERPRETATION

Initial Tests (lab, imaging)

  • If rupturing AAA is considered: complete blood chemistry (chemistries, PT/INR, PTT, type and cross), ECG
  • Ultrasound: simplest and least expensive diagnostic procedure with a high sensitivity (94–100%) and specificity (98–100%); test of choice for an asymptomatic AAA (1)[C]
  • Surveillance of asymptomatic aneurysm
    • 2.6 to 2.9 cm: Screen at 10-year intervals.
    • 3 to 3.9 cm: Screen at 3-year intervals.
    • 4 to 4.9 cm: Screen at 12-month intervals.
    • 5 to 5.4 cm: Screen every 6 months.
  • CT scans are preferred preoperative study (caution with IV contrast in renal failure) if a symptomatic AAA is suspected.
  • MRI/MRA can visualize AAA but is often not possible in emergent situations.
  • Abdominal x-rays can be diagnostic if calcifications exist; not a diagnostic tool of choice

Follow-Up Tests & Special Considerations

  • Evaluation for coronary artery disease is appropriate prior to elective AAA repair, including stress test, echocardiography, and ECG if appropriate.
  • If AAA was discovered at any location, then full assessment of entire aorta, including thoracic aorta and aortic valve, is recommended (1)[C].

Diagnostic Procedures/Other

ALERT

Use clinical judgment: Patients with known AAA having abdominal or back pain symptoms may be rupturing despite a negative CT scan.

Descriptive text is not available for this image TREATMENT

GENERAL MEASURES

  • Treat atherosclerotic risk factors: HTN, dyslipidemia, diabetes mellitus, and smoking (2)[A].
  • Smoking was associated with a 0.35 mm/year AAA growth, twice as fast as AAA growth in nonsmokers, and is the most important AAA outcome predictor (1).
  • Emergent treatment in unstable or symptomatic patients requires immediate vascular surgery consultation, adequate IV access and resuscitation, type and cross for multiple units, and rapid bedside ultrasound (1).
  • Less acute prevention of AAA rupture is elective repair and risk factor modification.

MEDICATION

  • β-Blockers, aspirin, and statins theoretically reduce the rate of growth of AAAs by decreasing shear wall stress, inflammation, and prevention of an intraluminal mural thrombus. However, there are conflicting RCT and meta-analysis trials. Because concomitant atherosclerosis is often a precipitating factor in AAAs, their use is recommended for reduced mortality in patients with coronary artery disease or its equivalents (3)[A].
  • The use of ACE inhibitors has shown to be inconclusive with regard to growth of AAA; however, studies do indicate a decreased rate of AAA rupture (3)[A].
  • Doxycycline and roxithromycin, theorized to decreased wall inflammation, have not been shown to have any effect on AAA (4).

SURGERY/OTHER PROCEDURES

Current recommendations are the following:

  • Elective
    • 5.5-cm diameter is threshold for repair in “average” patient (1)[C].
    • Younger, low-risk patients with long-life expectancy may prefer early repair.
    • Saccular aneurysms should be considered for elective repair (1)[C].
    • Women or AAA with high risk of rupture: Consider elective repair at 4.5 to 5 cm.
      • Consider delayed repair in high-risk patients.
      • 5% perioperative mortality for open elective repair (1)
  • High risk of rupture
    • Expansion >0.5 cm/year; poorly controlled HTN; smoking/severe COPD
  • High-risk patients for elective repair
    • Risk factors for open repair include age >75 years, COPD, chronic kidney disease with Cr >1.75, and suprarenal clamp site.
    • The leading cause of early mortality after AAA repair is coronary artery disease, with open AAA repair being much higher risk than endovascular AAA repair (1)[C].
  • The RCT IMPROVE trial showed a similar 30-day mortality for patients with ruptured AAA who underwent endovascular repair versus open repair (35.4% vs. 37.4%); 1-year follow-up all-cause mortality between the two groups (41.1% vs. 45.1%) (4)[A].
  • Perioperative morbidity rates are lower for EVAR, suggesting that an EVAR is preferable in patients with a ruptured AAA with poor prognostic factors for an open repair, such as SBP <80 mm Hg, age >80 years, Cr >1.3 on admission, ischemic heart disease, female sex, and hemoglobin <9.0 on admission (2),(4)[A].
  • Contraindications for AAA endovascular repair are an aortic neck length >32 mm and a ruptured AAA with aortic neck length <7 mm. In these patients, an open AAA repair is performed due to anatomical constrictions.

ADMISSION, INPATIENT, AND NURSING CONSIDERATIONS

Risk of abdominal compartment syndrome after repair, 4–12%; usually associated with large fluid resuscitation

Descriptive text is not available for this image ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

  • May do a CT scan 5 years after an open repair for possible late aortic dilatation or pseudoaneurysm (2)[C]
  • Follow-up imaging should be tailored to patient. Once renal function stabilizes postoperatively, a CT can be performed to evaluate the endograft (2)[C].
  • Aggressive risk factor modification always recommended postoperatively (2)[A].

DIET

Low-fat, low-salt, and low-caffeine diet; optimize nutrition prior to elective repair.

PATIENT EDUCATION

Smoking cessation, aerobic exercise, and aggressive control of atherosclerotic risk factors such as HTN

PROGNOSIS

  • Naturally progressive disorder, expands at an average rate of 0.3 to 0.4 cm/year; a fast expansion is considered >0.6 cm per year and should be evaluated for operative management.
  • Possibility of rupture increases with an aneurysm diameter of >5.5 cm or a fast rate of expansion (>0.5 cm over a 6-month period), continued cigarette use, female sex, recent surgery, uncontrolled HTN, and aneurysm couture.

COMPLICATIONS

  • Emergent AAA repair and elective AAA repair have similar complications, with a higher incidence in emergent AAA repair.
  • Complications include MI, respiratory failure, and acute kidney injury in the early period.
  • Late complications such as aortic graft infection, aortoenteric fistula, and graft occlusion have similar rates between emergent and elective repair.
  • Ischemic bowel and abdominal compartment syndrome are complications usually after a ruptured open AAA repair given the massive blood loss, increased operative time, and magnitude of fluid resuscitation.

Authors

Jeffrey Chen, MD

REFERENCES

  1. Chaikof EL, Dalman RL, Eskandari MK, et al. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018;67(1):2–77.e2.  [PMID:29268916]
  2. LeFevre ML; for U.S. Preventive Services Task Force. Screening for abdominal aortic aneurysm: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2014;161(4):281–290.  [PMID:24957320]
  3. Guessous I, Periard D, Lorenzetti D, et al. The efficacy of pharmacotherapy for decreasing the expansion rate of abdominal aortic aneurysms: a systematic review and meta-analysis. PLoS One. 2008;3(3):e1895.  [PMID:18365027]
  4. Braithwaite B, Cheshire NJ, Greenhalgh RM, et al; for IMPROVE Trial Investigators. Endovascular strategy or open repair for ruptured abdominal aortic aneurysm: one-year outcomes from the IMPROVE randomized trial. Eur Heart J. 2015;36(31):2061–2069.  [PMID:25855369]

ADDITIONAL READING

Aggarwal S, Qamar A, Sharma V, et al. Abdominal aortic aneurysm: a comprehensive review. Exp Clin Cardiol. 2011;16(1):11–15.  [PMID:21523201]

Descriptive text is not available for this image SEE ALSO

Aortic Dissection; Arteritis, Temporal; Ehlers-Danlos Syndrome; Marfan Syndrome; Polyarteritis Nodosa; Turner Syndrome

Descriptive text is not available for this image CODES

ICD10

  • I71.4 Abdominal aortic aneurysm, without rupture
  • I71.3 Abdominal aortic aneurysm, ruptured

SNOMED

  • 233985008 Abdominal aortic aneurysm (disorder)
  • 14336007 Ruptured abdominal aortic aneurysm
  • 75878002 Abdominal aortic aneurysm without rupture

CLINICAL PEARLS

  • Men with a smoking history aged 65 to 75 years should undergo a one-time screening abdominal ultrasound to evaluate for an AAA. Men and women with a first degree relative with an AAA should be considered for a screening abdominal ultrasound.
  • Larger AAAs should be screened more often, with elective repair with AAA >5.5 cm or an expansion of >0.5 cm every 6 months.
  • Patients with a ruptured AAA present in shock, with abdominal pain and a pulsatile mass. A bedside ultrasound should be done quickly to evaluate for an AAA, or an emergent CT scan can be performed if the patient is hemodynamically stable.
  • AAA are treated either open or endovascularly as an elective or emergent procedure. 30-day and 1-year mortality between the two methods remain the same; however, there is increased mortality with an emergent AAA repair.
  • Patients require aggressive risk factor modification, especially smoking cessation.

Last Updated: 2026

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