ABDOMINAL AORTIC ANEURYSM

ABDOMINAL AORTIC ANEURYSM

ABDOMINAL AORTIC ANEURYSM

An abdominal aortic aneurysm (AAA) is a bulge or swelling in the aorta, the main blood vessel that runs from the heart down through the chest and tummy.

Symptoms and Signs

Although 80% of 5-cm infrarenal aneurysms are palpable on routine physical examination, most aneurysms are discovered on ultrasound or CT imag­ing as part of a screening program or during the evaluation of unrelated abdominal symptoms.

Aneurysmal expansion may be accompanied by pain that is mild to severe midabdominal discomfort often radiating to the lower back. The pain may be constant or intermittent and is exacerbated by even gentle pressure on the aneurysm sack. Pain may also accompany inflammatory aneurysms. Most aneurysms have a thick layer of thrombus lining the aneurysmal sac, but embolization to the lower extremities is rarely seen.

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The sudden escape of blood into the retro­peritoneal space causes severe pain, a palpable abdominal mass, and hypotension. Free rupture into the peritoneal cavity is a lethal event.

Diagnosis

Abdominal ultrasonography is the diagnostic study of choice for initial screening for the presence of an aneu­rysm. In approximately three-quarters of patients with aneurysms, curvilinear calcifications outlining portions of the aneurysm wall may be visible on plain films of the abdomen or back. CT scans provide a more reliable assess­ment of aneurysm diameter and should be done when the aneurysm nears the diameter threshold (5.5 cm) for treat­ment. Contrast-enhanced CT scans show the arteries above and below the aneurysm. The visualization of this vascula­ture is essential for planning repair.

Once an aneurysm is identified, routine follow-up with ultrasound will determine size and growth rate. The fre­quency of imaging depends on aneurysm size ranging from every 2 years for aneurysms smaller than 4 cm to every 6 months for aneurysms at or approaching 5 cm. When an aneurysm measures approximately 5 cm, a CTA with contrast should be done to more accurately assess the size of the aneurysm and define the anatomy.

Treatment

Elective Repair

In general, elective repair is indicated for aortic aneurysms larger than 5.5 cm in diameter or aneurysms that have undergone rapid expansion (more than 0.5 cm in 6 months). Symptoms such as pain or tenderness may indi­cate impending rupture and require urgent repair regard­less of the aneurysm’s diameter.

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Aneurysmal Rupture

A ruptured aneurysm is a lethal event. Approximately half the patients exsanguinate prior to reaching a hospital. In the remainder, bleeding may be temporarily contained in the retroperitoneum (contained rupture), allowing the patient to undergo emergent surgery. However, only half of those patients will survive. Endovascular repair is available for ruptured aneurysm treatment in most major vascular cen­ters, with the results offering some improvement over open repair for these critically ill patients.

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