Ruptured abdominal aortic aneurysm.

Most abdominal aortic aneurysms are true aneurysms. A true aortic aneurysm is a localized dilatation of the aorta caused by weakening of its wall; it involves all three layers (intima, media and adventitia) of the arterial wall. Aneurysms may develop in any segment of the aorta, but most involve the aortic segment below the renal arteries. An aortic diameter of 3 cm or more is used to define an abdominal aortic aneurysm (1). Aneurysmal dilatation of the abdominal aorta is a disease of aging and is rare before age 50 but is found in 2%–4% of the population older than 50 years (2). A retroperitoneal hematoma adjacent to an abdominal aortic aneurysm is the most common imaging finding of rupture (3). Extension of hemorrhage into the retroperitoneum, including the perirenal and pararenal spaces, psoas muscles and peritoneum, is a common occurrence. Intraperitoneal extravasation may be an immediate or a delayed finding. Patients who present with abdominal pain, a large abdominal aortic aneurysm, and no frank rupture pose a diagnostic dilemma. The symptoms may be attributable to aneurysmal instability,impending rupture, or a contained leak. Computed tomography (CT) is the modality of choice for evaluation of acute aortic syndrome, because of the speed of the examination and the widespread availability of CT. Ruptured abdominal aortic aneurysm (r-AAA) is still keeping an important clinical situation which needs urgent diagnosis and surgical treatment with a high mortality and morbidity rates despite the novel technological development (5). A retroperitoneal hematoma adjacent to an abdominal aortic aneurysm is the most common imaging finding of abdominal aortic aneurysm rupture (3,4). Periaortic blood may extend into the perirenal space, pararenal space, or the psoas muscles. Intraperitoneal extension may be an immediate or a delayed finding. These findings are readily visible on unenhanced CT images, which may have been obtained for another indication or as part of an aneurysm evaluation protocol. On contrast enhanced CT images, active extravasation of contrast material is frequently demonstrated.