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Essential Features

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  • • Permanent aortic dilation (at least 50%)

    • Classified by etiology (degenerative, inflammatory, mechanical, congenital, dissecting) and by shape (saccular, fusiform)

    • Up to 25% of patients have symptoms of aortoiliac occlusive disease as well

    • Most are infrarenal; decreased vasa vasorum and elastic lamellae may predispose to aneurysm formation

    • Rupture risk correlates with size, following law of LaPlace

    • Average expansion rate of 0.4 cm/y depends on aneurysm size, diastolic blood pressure, and chronic obstructive pulmonary disease (COPD)

    • For AAA measuring 5.0–5.5 cm, rupture risk is 40% at 5 years

    Suprarenal: Uncommon; extends proximal to renal arteries; low risk for rupture until exceeds 6–7 cm

    Ruptured: Most often ruptures posterolaterally to left; if exsanguination delayed, likely contained rupture that eventually becomes free rupture

    Inflammatory: Characterized by inflammatory response external to aneurysmal wall, with inflammation usually confined to anterior aorta; 25% have ureteral obstruction, which results in dense, shiny fibrotic reaction enveloping adjacent viscera

    Infected (mycotic): Bacterial contamination of preexisting aneurysm (different from Salmonella causing false aneurysm); gram-negative infections result in higher rupture rates

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Epidemiology

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  • • Ruptured AAA is the 13th leading cause of death in the United States (15,000 deaths yearly)

    • Present in 2% of population and incidence is increasing

    • More men affected than women (4:1)

    • 5% of patients with coronary artery disease have AAA

    • 50% of patients with femoral or popliteal aneurysms have AAA

    • 19% incidence among first-degree relatives

    Rare causes:

    • –Marfan syndrome

      –Ehlers-Danlos syndrome

      –Behçet disease

      –Syphilis

      –Long-term sequelae of aortic dissection

    Risks:

    • –Smoking

      –Hypertension (HTN)

      –COPD

    • Diabetes appears to exert protective effect

    • Increased incidence of rupture during fall and winter months

    Strep, Haemophilus, Staph, E coli, other gram-negative pathogens, and fungi identified in infected AAA

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Clinical Findings

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Symptoms and Signs

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  • • Rarely produces symptoms if intact

    • Painless, pulsatile abdominal mass above umbilicus; may be uncomfortable on palpation

    • Palpation may be difficult in obese patients

    • Rarely produces back pain from pressure on nerves

    • Severe paincaused by inflammatory or ruptured AAA or acute expansion

    • Congestive heart failure from aortocaval fistula, GI bleed from duodenal erosion, and pyelonephritis from ureteral obstruction are rare

    • Rupture causes sudden, severe abdominal/back pain radiating to back or inguinal area, faintness or syncope, shock; often tender pulsatile mass present

    Triad for rupture: Pain, pulsatile abdominal mass, hypotension found in < 67% of patients

    Inflammatory: Abdominal pain, tender AAA

    Infected: Rapidly enlarging tender pulsatile mass, fever

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Laboratory Findings

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  • • CBC abnormal

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Imaging Findings

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  • Abdominal x-ray: 20% calcifications in outer aortic wall on lateral view

    US

    • –Inexpensive screening test, measures size and position

      –Used in cases of groin pseudoaneurysm to evaluate proximal anastomosis in abdomen

    CT scan

    • –Diagnostic, accurate sizing, and provides information about anatomy: renal ...

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