Elements of Surgery

by Robert Liston

The blood contained within the aneurismal sac, being comparatively motionless, coagulates, and the coagulum is attached to the inner surface; at first it contains red globules, but it afterwards loses them, and becomes of a pale hue, consisting solely of fibrin. This coating gradually increases, and attains no small thickness, fresh portions of fibrin being superadded in concentric laminæ. These layers are chiefly deposited from the blood within the cavity, but they also appear to receive addition from lymph being effused by the vessels proper to the original parietes of the tumour. By such thickening, it can be easily conceived that the pulsation will be somewhat lessened. In large aneurisms the accumulation and deposit of fibrin may be much greater at some points than at others, and hence pulsation may be rendered “not equal in all directions.” It is not, however, diminished to any great extent; for absorption of one or more points occurs, and the coating is again attenuated.

In some rare cases the deposition of fibrin has gone on gradually accumulating, filled completely the aneurismal cavity, and thus effected a spontaneous cure, the remaining solid tumour imperceptibly diminishing by the action of the absorbents. After obliteration of the aneurismal cavity, the fibrin is generally deposited in so great quantity as to occupy the calibre of the vessel above and below the tumour, obstructing the progress of the blood, causing it to flow by the smaller and collateral branches, and effecting a spontaneous cure, somewhat similar to that produced by the artificial application of a ligature. Coagula are seldom formed in the dilated vessel, to whatever size it may be enlarged, unless there is fissure of the internal coat; for in no other way can a portion of the blood readily become stagnant, while the calibre of the vessel remains pervious. There is in my collection a preparation of dilated aorta, to the coats of which adheres a large firm coagulum. Occasionally, though rarely, a dilatation of the internal coats is met with accompanied by thinning of the external ones. Of this sort of diverticulum, there is also a good specimen in the collection here alluded to.

A spontaneous cure may also be accomplished from the original aneurism being compressed by one of a more recent origin, causing ultimate obliteration of the canal. Of this I recollect one remarkable instance; the patient was afflicted with an aneurism of the axillary artery, which had attained a large size, and the cure for the disease in this situation being then unknown or unattempted, the patient was considered as lost; but some time after the tumour began to diminish, and disappeared. The patient died; and the cause of death was found to be the giving way of an aneurismal tumour of the arteria anonyma, which was situated so closely to the aneurism of the subclavian as to have acted as a mechanical compress, causing obliteration of the vessel at that point.

When a cure has been effected, the vessel is found to be converted into a dense and impervious cord at the site of the tumour. The canal above is dilated; the coats are thickened, especially the middle; and from the thickening and increased action of the fibres, the internal coat becomes somewhat rugous, the rugæ being in a transverse direction.

The aneurismal tumour in general increases, and approaches the surface, involving and destroying all the intervening textures. If resisted in its enlargement by bone, even this is not sufficient to impede its progress; the bone is absorbed, and perhaps ulcerated, at the point where it is compressed by the tumour. The osseous is more liable to destruction from this cause than the cartilaginous tissue, contrary to what occurs from compression by abscess. Ultimately the sac gives way, and its contents are discharged either externally, or into an internal cavity or canal, in consequence of its parietes sloughing from the compression made by the tumour; and such termination is instantly fatal.

An aneurism of the descending aorta, in a great measure one from dilatation, is here represented: the patient also laboured under popliteal aneurism of one limb, and inguinal of the other. He died suddenly, in consequence of the giving way of the internal tumour. The escape of blood into the cellular tissue may even take place to such an extent as to prove fatal in a few hours. The disease may also prove fatal by mere compression, as of the trachea, impeding breathing, and inducing disease of the respiratory organs; or by pressure on the gullet preventing the passage of food: in the latter case, however, the dissolution is generally more sudden, in consequence of the compressing part of the tumour giving way, and the contents being evacuated into the stomach or mouth. If the aneurism compress a plexus of nerves, or the spinal chord itself, the anterior part of the vertebræ having been previously absorbed, paralysis is produced.

In consequence of aneurism, the circulation of blood in the vessel is obstructed; hence the collateral branches above the tumour become enlarged, and through them the circulation is continued; by their anastomosis with collateral branches which arise below the seat of the tumour, a portion of the fluid is brought back into the canal of the original artery. The circumstance of collateral enlargement used to be distinctly enough demonstrated in amputation, one of the old cures for the disease.

The tumour may be suddenly increased by a portion of the parietes giving way, and the blood being propelled into the cellular tissue, which becomes thereby condensed, and supplies the deficiency in the original sac; diffuse is thus superadded to the true or encysted aneurism.

The disease is generally accompanied with great pain, the neighbouring nerves being much stretched by the enlargement of the tumour, as in the axilla or ham; in these situations also the limb below the aneurism is much swollen from the compression of the absorbents and veins and consequent infiltration into the cellular tissue. Diffused aneurism from wounds, and the other species of the disease, will be afterwards treated of.