Aortic blebs: possible site of aneurysm rupture.

Although the growth and rupture of abdominal aortic aneurysms are commonly explained by Laplace's law, the final events that precede aneurysm rupture are not fully understood. Local excrescences within the wall of abdominal aortic aneurysms were observed in four of five patients studied with preoperative CT scanning, and were removed from six patients at the time of surgery. These protrusions were filled with thrombus, and on histologic examination marked attenuation of the aortic wall, focal loss of elastic fibers, and inflammatory cell infiltrates of lymphocytes, plasma cells, and occasional multinucleate giant cells were seen. The presence of these blebs and their microscopic characteristics suggest their potential as a mechanism for rupture and recognition of this deformity by use of abdominal CT scanning may indicate the necessity for prompt surgical intervention. Further careful clinicopathologic correlation is required to clearly establish these localized defects in the aneurysm wall as a cause for rupture.