Spontaneous cure by natural methods is brought about in one of the following ways: (a) By consolidation of laminated clots. (b) A portion of the clot may become detached and plug the vessel on the distal side, effecting the same occlusion there that is produced with a ligature; in some cases the vessel may be occluded above the sac by a clot from the heart. (c) That which occurs naturally may be caused by accident as the result of some trifling injury. (d) The clot contained within the sac may have become infected, so that suppuration with necrosis of the sac contents is produced. In connection with this there is sufficient acute arteritis to occlude the vessel, and the resulting abscess within the sac may be opened and its contents cleared out. This method is extremely rare and can only terminate happily when the surgeon intervenes promptly.
In an aneurysm in which spontaneous cure has occurred there may be progressive condensation of its contents, obliteration and partial reduction in size, and a slow process of absorption.
The importance of collateral circulation, in recovery from aneurysm, cannot be overestimated, as only by taking advantage of it is it possible to furnish blood for the needs of the part affected. There is no vessel with which the surgeon can interfere where natural provisions in this direction appear insufficient ([Fig. 148]).
Certain conditions predispose to aneurysm of the idiopathic type, such as age, with its accompaniment of arteriosclerosis; syphilis, with its well-known tendency to chronic endarteritis; occupation and sex, in that it is most frequent in those who are liable to violent exertion and dissipation, because of the well-known tendency to arterial structural changes after excesses of all kinds. Again, aneurysm may be the secondary result of embolism when an embolus leads to a local arteritis with disorganization.
Fig. 147
Fig. 148
Multiple aneurysms of the mesenteric arteries. (Eppinger.)
Change in the trunk after ligature; with anastomosing vessel. (Erichsen.)