CELLULAR CONTENT AND PERMEABILITY OF INTRALUMINAL THROMBUS IN ABDOMINAL AORTIC-ANEURYSM

Purpose: A pathologic feature commonly associated with abdominal aorti c aneurysms is the presence of variably sized and shaped intraluminal thrombus, which may be fundamental to the disease process. However, th e precise role of the intraluminal thrombus in the formation, enlargem ent, and rupture of abdominal aortic aneurysms is unknown. The hypothe sis tested in this study was whether there were structural features of aortic thrombi to suggest that it may be involved in the pathogenesis of abdominal aortic aneurysms. We have investigated this hypothesis u sing a variety of structural and biochemical techniques. Methods: Test s performed were light, transmission, and scanning electron microscopy ; fluid permeability measurements; and Western blots. Results: Intralu minal thrombus found in abdominal aortic aneurysms is structurally com plex and is traversed from the luminal to abluminal surface by a conti nuous network of interconnected canaliculi. Quantitative microscopic a nalysis of the thrombus shows cellular penetration for at least 1 cm f rom the luminal surface of the thrombus. Macromolecular penetration ma y be unrestricted throughout the entire thickness of the thrombus. Fib rin deposition occurred throughout the thrombus, whereas fibrin degrad ation occurred principally at the abluminal surface. Conclusions: Thes e principally structural studies support the hypothesis that the throm bus is a self-sustaining entity that may have significance in the path ophysiologic mechanism of abdominal aortic aneurysms.