RT Book, Section A1 Doherty, Gerard M. SR Print(0) ID 58091001 T1 Abdominal Aortic Aneurysm (AAA) T2 Quick Answers Surgery YR 2010 FD 2010 PB The McGraw-Hill Companies PP New York, NY SN LK accesssurgery.mhmedical.com/content.aspx?aid=58091001 RD 2024/03/28 AB • 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