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ABDOMINAL AORTIC ANEURYSMS

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An abdominal aortic aneurysm (AAA) is commonly ≥3.0 cm in diameter and can be a significant cause of morbidity and mortality. Symptomatic aneurysms and those ≥5.0 cm in diameter frequently require prompt operative repair.

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Clinical Features

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An acute rupturing AAA is an emergent condition that will lead to death if not rapidly identified and repaired. The classically described presentation of a ruptured AAA is an older male smoker with atherosclerosis who presents with sudden severe back or abdominal pain, hypotension, and a pulsatile abdominal mass. Patients may also present with syncope or pain that localizes to the flank, groin, hip, or abdomen.

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Half of patients with a rupturing aneurysm describe a ripping or tearing pain that is severe and abrupt in onset. On examination, patients may have a tender pulsatile abdominal mass, although this finding may be challenging to identify in obese patients. Patients with a ruptured AAA may present with persistent hypotension due to blood loss, although this may transiently improve due to compensatory mechanisms. Femoral pulsations are typically normal. Retroperitoneal hemorrhage may rarely present with external findings such as periumbilical ecchymosis (Cullen's sign), flank ecchymosis (Grey–Turner's sign), or a scrotal hematoma.

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Aortoenteric fistulas, although rare, may present as gastrointestinal bleeding with either a small sentinel bleed or a massive life-threatening hemorrhage. Patients with prior aortic grafting are at an increased risk of this complication. The duodenum is a common site for fistula formation, and patients with this complication may present with hematemesis, melena, or hematochezia. Aortovenous fistulas can lead to high-output cardiac failure with decreased arterial blood flow distal to the fistula.

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An uncommon presentation of AAA is rupture into the retroperitoneum, where significant fibrosis may lead to a chronic contained rupture. These patients can appear well and may complain of pain for an extended period of time before the diagnosis is made.

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Clinicians may discover an asymptomatic AAA on physical examination or as an incidental finding on a radiologic study. Refer patients with a newly diagnosed AAA to a vascular surgeon for evaluation, keeping in mind that aneurysms larger than 5 cm in diameter are at a greater risk for rupture.

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Diagnosis and Differential

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Identifying a new AAA can be a challenging diagnosis. When the diagnosis is not initially identified, renal colic is the most common incorrect initial diagnosis. Consider this diagnosis in patients with symptoms of back pain, an intraabdominal process, testicular torsion, or gastrointestinal bleeding.

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When the diagnosis is unclear, consider additional studies to further evaluate patients with symptoms concerning for an expanding or rupturing AAA. Bedside abdominal ultrasound has >90% sensitivity for identifying AAA and can be used to accurately measure the diameter of the aneurysm (see Fig. 27-1), although aortic rupture or retroperitoneal bleed cannot be reliably identified with this modality. Computed tomography ...

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