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CASE SCENARIO

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A 65-year-old male with a past medical history notable for hypertension, hyperlipidemia, and a 40 pack-year smoking history complicated by chronic obstructive pulmonary disease (COPD) presents to the emergency room with 2 hours of sudden-onset abdominal and lower back pain. Shortly after the pain began, he felt dizzy and nauseated. He was subsequently brought to the emergency room by ambulance.

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Upon evaluation, the patient is found to be tachycardic and hypotensive with a systolic blood pressure of 90. He is slightly somnolent but oriented to person, place, and time. His abdomen is distended and mildly tender to palpation without overt signs of peritonitis. A prominent pulsatile midline mass is also noted. The bilateral flanks demonstrate ecchymosis. Femoral, popliteal, and distal lower extremity pulses are diminished but palpable, and all extremities are mottled and cool. His labs are notable for a hematocrit of 33, white blood cell count of 12, BUN of 20, and Cr of 1.4.

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EPIDEMIOLOGY

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Acute diseases of the aorta present life-threatening emergencies. The following discussion aims to equip the reader with the understanding required for prompt diagnosis and initial management of aortic aneurysm and dissection.

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Abdominal Aortic Aneurysm (AAA)

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An arterial aneurysm is a localized, permanent, focal dilation that exceeds the normal vessel diameter by 50% or greater.1,2 Measurements taken with a variety of radiographic and in situ techniques have demonstrated that the normal caliber of the abdominal aorta varies in size by location and by gender. The supraceliac aorta is largest, with a diameter ranging from 2.50 to 2.72 cm in men and 2.10 to 2.31 cm in women, whereas the infrarenal aorta ranges from 1.99 to 2.39 cm in men and 1.66 to 2.16 cm in women.3 In general, however, an abdominal aortic aneurysm is defined by an aortic diameter greater than or equal to 3 cm, or a 1.5-fold increase in a patient’s normal aortic diameter.4 In the vast majority of cases, the isolated area of aneurysmal dilation is confined to the infrarenal aorta (~80%).4,5

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The incidence of AAA ranges from approximately 1.5% to just over 3% in various studies,4,5 and the rate of aneurysm formation is two- to six-fold higher in men compared to women.3 Rates as high as 10% to 15% have been noted in populations with a strong family history of aneurysmal disease and in long-term smokers.6

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Aortic Dissection

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The incidence of acute aortic dissection is approximately 3 per 100,000 person-years.6,7 Dissections typically occur between the sixth and eighth decades of life and affect males more commonly than females. Accurate diagnosis and timely intervention are paramount to minimize morbidity and mortality. Studies have demonstrated that without treatment, most patients with acute dissection die within 3 months of diagnosis.7...

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