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Updated: Dec 7 2021

Abdominal Aortic Aneurysm

Images aa.jpg
  • Snapshot
    • A 67-year-old man presents to his primary care physician due to vague epigastric discomfort. He denies it being associated with meals and reports that this pain occurred insidiously. Medical history is significant for hypertension. He has been smoking 1-pack of cigarettes per day for the past 30 years. On physical exam, he has a pulsatile abdominal mass that is tender to palpation. An abdominal ultrasound is performed, which demonstrates a 6 cm abdominal aortic aneurysm. He is scheduled for an elective abdominal repair surgery for the following day.
  • SUmmary
    • Abdominal aortic aneurysm (AAA) is a condition characterized by a segmental and full-thickness dilation of the abdominal aorta. It is caused by inflammation and stress upon the aortic wall leading to dilatation and aneurysm. It typically presents in older men 60-70 years of age. Patients often present lower back pain and a pulsatile abdominal mass, with bruits heard on auscultation.
    • Diagnosis is made via imaging revealing an aortic diameter greater than 3cm. CT angiography is typically used following ultrasound for further characterization and intervention planning. 
    • Treatment is usually surgical repair via endovascular or open surgical operation and is recommended for aneurysms larger than 5.5 cm, expanding greater than 1 cm per year, or severe symptoms.
  • Epidemiology
    • Incidence
      • very common > 1/10,000
    • Demographics
      • 4:1 male to female ratio
    • Location
      • most AAA are infrarenal
        • 1/3 of AAA can extend into the iliac arteries
    • Risk factors
      • age
      • male gender
      • cigarette smoking (greatest risk factor)
      • family history
      • Caucasian race
      • atherosclerosis
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • inflammation leads to the degradation of proteins within connective tissue
          • aortic wall loses structural integrity
            • vessels widen and dilate leading to dilation and rupture
      • pathoanatomy
        • the abdominal aorta is a retroperitoneal structure that
          • begins in the hiatus of the diaphragm
          • bifurcates into the right and left iliac common arteries
            • these arteries can also become aneurysmal
        • an aneurysm typically develops below the renal arteries and above the common iliac arteries
      • cell biology
        • elastin fibers become disrupted and collagen becomes degraded
          • results in a loss of elasticity in the aortic wall
    • Associated conditions
      • weakening of the aortic wall can lead to tears causing aortic dissection
      • severe aneurysms can ultimately lead to aortic rupture
  • Anatomy
    • The aorta originates from the left ventricle and travels inferiorly until it bifurcates infrarenally around L4 
      •  abdominal aortic aneurysms most often occur below the kidneys and above the bifurcation of the aorta
  • Presentation
    • Symptoms
      • asymptomatic (the majority of cases)
        • an enlarged abdominal mass and an abdominal bruit may be found
      • if symptomatic
        • abdominal, back, or flank pain
        • in ruptured cases
          • severe pain and hypotension
    • Physical exam
      • auscultation findings
        • abdominal bruit
      • inspection
        • pulsatile mass
  • Imaging
    • Ultrasound
      • indication
        • USPSTF recommends that screen be performed 1 time in men who
          • are 65-75 years of age
          • smoked at any time
        • serial imaging in patients with an abdominal aortic aneurysm (AAA) < 5 cm
      • preferred views
        • longitudinal and transverse views of the abdomen
        • identification of the abdominal aorta and both common iliac arteries
      • findings
        • aortic dilation greater than 3 cm
        • hypoechoic appearance of thrombi
      • sensitivity
        • low sensitivity for leaks, involvement of other branches or suprarenal arteries
    • Abdominal CT (contrast-enhanced)
      • indication
        • in symptomatic patients who are hemodynamically stable
        • for preintervention planning
      • views
        • scan from diaphragm to iliofemoral arteries including the renal arteries and bifurcation of the aorta
      • findings
        • dilation of the aorta greater than 3 cm
        • presence of thrombi which are nonenhanced and hypodense
  • Differential
    • Mesenteric ischemia
      • findings found in mesenteric ischemia and not abdominal aortic aneurysm
        • more pronounced GI symptoms of diarrhea, vomiting, and nausea
        • weight loss
    • Myocardial infarction
      • findings found in myocardial infarction and not abdominal aortic aneurysm
        • ECG findings (i.e. STEMI, NSTEMI)
        • more severe chest pain
    • Peptic ulcer disease
      • findings found in peptic ulcer disease and not abdominal aortic aneurysm
        • burning associated with eating food or drinking
  • Treatment
    • Conservative
      • smoking cessation
        • indication
          • for all patients
        • outcomes
          • proven to decrease the rate of aneurysm expansion
    • Operative
      • AAA repair
        • indication
          • ruptured AAA (surgical emergency)
          • symptomatic and unruptured cases
            • abdominal aortic aneurysm ≥ 5.5 cm
            • AAA smaller than 5.5cm, but rapidly expanding (>0.5cm over 6 months)
  • Technique
    • Endovascular aneurysm repair (EVAR)
      • approach
        • typically performed by vascular surgery with fluoroscopic image guidance
      • technique
        • image-guided stent placement most often via femoral or common iliac artery access
      • complications
        • bleeding
        • infection
        • endoleak
        • thrombosis
    • Open surgical repair
      • approach
        • typically performed by cardiothoracic surgery via open incision
      • technique
        • incision via transabdominal or retroperitoneal approach
        • removal of aneurysm and placement of graft
      • complications
        • endoleak
        • bleeding
        • infection
        • thrombosis
        • incisional hernia
  • Complications
    • Aneurysm rupture
      • incidence
        • increased risk relative to size of the aneurysm
          • risk is 3-15% in aneurysms greater than 5.5 cm in diameter 
      • risk factors
        • advanced age
        • male sex
        • atherosclerosis
      • treatment
        • emergent surgical repair
    • Embolism
      • incidence
        • around 1-2% of patients with aneurysm repair experienced venous thromboembolism
      • risk factors
        • coagulopathy
      • treatment
        • anticoagulation
    • Aortic dissection
      • incidence
        • increased risk with increased aneurysm size
          • estimated 3.7% of patients with aneurysms> 6 cm
      • risk factors
        • hypertension
        • smoking
        • Marfan's syndrome
      • treatment
        • surgical repair
  • Prognosis
    • Overall poor prognosis
      • greater than 50% of patients with AAA die prior to arrival to the emergency room
      • poor prognostic factors include
        • age > 80 years old
        • massive blood loss
        • female gender
      • survival with treatment
        • 1-year survival rate for treated patients estimated around ~90%
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