Classification.

—For surgical purposes there is no better classification than the one used by Eve:

1. Sacculated Aneurysms.

—The sacculated are the most common. They assume various shapes and dimensions, and may be seen anywhere in the body. The opening between the sac and the main vessel may vary in size. These sacs are usually strengthened by plastic exudate in and around them, and condensation of surrounding tissue. In thickness they vary from 1 Cm. to the thinnest which will sustain blood pressure. In old scars may be found a stratiform or layer-like arrangement, especially where the blood stream is less active. Should spontaneous cure take place the sac may be obliterated, while later calcific or other changes in the old scar may occur. When the outer portion of such a sac has disappeared and the inner coat is pushed out so as to assume, apparently, a secondary aneurysmal arrangement, the condition is referred to as a hernial aneurysm. When the ordinary sacculation gives way as the result of necrosis, of pressure from within, or loss of support from without, the opening first made is usually small and the extravasation outside the true sac will depend upon the nature and resistance of the surrounding tissues. In this way a diffuse aneurysm is formed, which is one of the varieties of false aneurysm.

2. Fusiform Aneurysms.

—Fusiform aneurysms are more or less tubular and spindle-like dilatations of arterial trunks, in whose walls may occur the changes common to all these lesions, the dilatation rarely being sufficiently large to permit of laminated coagula unless a sacculation occurs later at some particular portion ([Fig. 149]).

Fig. 149

Fusiform aneurysm of popliteal artery, due to arterial disease (man aged 59), requiring amputation of thigh on account of gangrene. (Lexer.)