Abdominal aortic aneurysm
المؤلف:
James Carton
المصدر:
Oxford Handbook of Clinical Pathology 2024
الجزء والصفحة:
3rd edition , p51
2025-01-07
913
Definition
• A localized permanent dilation of the abdominal aorta >3 cm in diameter.
Epidemiology
• Incidence is reported to be 5– 10%.
Aetiology
• Almost all are caused by aortic atherosclerosis.
Pathogenesis
• Proteolytic enzymes weaken the media of the aorta, leading to aneurysmal change. • Increased levels of matrix metalloproteinases have been found in aneurysmal aortas. these enzymes are known to degrade elastin.
Presentation • Unruptured aneurysms are often asymptomatic and most are discovered incidentally on abdominal examination or imaging.
• Ruptured abdominal aortic aneurysms present as a surgical emergency with abdominal pain and shock.
Macroscopy
• the aorta is dilated, usually below the level of the renal arteries.
• extensive atherosclerosis is invariably present, often with secondary thrombosis and calcification.
Histopathology
• Aortic atherosclerosis shows intimal collections of lipid, inflammatory cells, and fibrosis. Complicated lesions may show haemorrhage in the plaque or overlying thrombus.
• Aortic aneurysms show severe atherosclerosis with marked loss of the media layer.
Prognosis
• the natural history is that of gradual enlargement.
• Risk of rupture is exponentially related to the diameter.
• Mortality after rupture exceeds 80%.
• elective surgical repair should be considered for aneurysms with a maximum diameter of 5.5 cm or more.
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