90 Virchow's Archiv für path. Anat., etc., Band xl. pp. 380, 408.
Dilatation and ulceration of the bile-ducts were the principal causes of hepatic abscess, as ascertained by Von Baerensprung, in the Berlin Pathological Institute. Duodenal catarrh involving the orifice of the common duct, catarrh of the biliary passages leading to obstruction, and plugging with a gall-stone have resulted in abscess, the initial lesion being probably rupture of one or more of the finer tubes or inflammation leading to suppuration.91
91 Grainger Stewart, The Edinburgh Medical Journal, January, 1873.
Finally, a considerable proportion of cases of hepatic abscess arise under unknown conditions. In such cases, however, it is usually found that there has been more or less indulgence in alcoholic drinks, or the liver has been taxed by excesses in the use of rich foods and condiments, or exposure to extreme degrees of temperature has occurred. In the interior valley of this continent, where hepatic abscess is comparatively common, the causes are to be found in malarial influences, in alcoholic indulgence, in dysenteric attacks the product of climatic variations and improper alimentation, and in the formation and arrest in transitu of hepatic calculi also the result of long-continued gastro-duodenal and biliary catarrh.
PATHOLOGICAL ANATOMY.—Great differences of opinion have been expressed as to the initial lesions in hepatic abscess. It is probable, however, that these differences are due to the character of the abscess. Some have their origin in the hepatic cells, others in the connective tissue, and others still in the vessels. There may be a number of points at which the suppurative process begins, or it may be limited to one. Virchow92 describes the initial lesion as beginning in the cells, which first become coarsely granular, then opaque, and finally soften, and pus appears. Klebs, who maintains the constant agency of septic micrococci, affirms that the changes in the cells are due to compression exerted by the mass of these organisms distending the neighboring vessels, and then suppuration begins on the portal side of the lobules. Liebermeister originally held that the initial lesion is in the connective tissue; and this view is also supported by Köster, who brings to bear experimental data. In the walls of the vessels of the connective tissue and about them, between the hepatic cells, great numbers of lymphoid cells accumulate. The intercellular spaces are also distended with plasma and round cells, and in the vicinity of the central vein the swollen hepatic cells are pressed together; soon pus-corpuscles appear, and the proper anatomical elements are broken up into a diffluent mass composed of fat-granules, pus-corpuscles, and disintegrating hepatic cells.
92 Archiv für path. Anat., etc., Band iv. p. 314.
When suppurative hepatitis arises from an embolus, or emboli, the first step is the change in the appearance of the acini, which are enlarged and grow softer by disintegration of their cells; then at the centre a yellowish spot appears, and is made up of the detritus, granules of fat, and pus. Surrounding such softening portions of the hepatic tissue is a zone of congestion. When the morbid processes are excited by emboli, there will be as many centres of pus-formation as there are particles distributed by the vessels—from two or three to fifty or more. They may be uniformly distributed through the organ or be collected in one part. Emboli conveyed by the portal vein will be arranged with a certain regularity and through the substance of the liver, whilst those coming from some part of the systemic circulation tend to form at the periphery under the capsule. Small abscesses in close proximity unite ultimately by the softening and disintegration of the intervening tissue.
In the so-called tropical abscess, which is the variety so frequently met with in the interior of this country, the mode of development is different from the embolic, above described. Owing to the deposit of some morbific matter whose nature is now unknown, the vessels dilate and hyperæmia of the part to become the seat of suppuration ensues. The cells become cloudy, granular, and opaque from the deposit of an albuminous matter in them. Within the area of congestion a yellowish spot soon appears, surrounded by a translucent, pale-gray ring, and here suppuration begins; the neighboring cells disintegrate and a purulent collection is formed, which enlarges by the destruction in succession of the adjacent portions of hepatic tissue. Whilst this process is going on there is a border of deep congestion about the abscess, fading off gradually into the normal tint of the hepatic parenchyma; the walls of the abscess are rough and irregular from projections of tissue just beginning to disintegrate, and the pus burrows in various directions more or less deeply into the softening parts. The size to which such purulent collections attain is largely determined by the condition of the liver as a whole. If the organ attacked is healthy otherwise and the general health is not deteriorated, the area of the abscess may be limited by a well-defined membrane and continue inactive for a long time. This limiting membrane is of inflammatory origin, developed from the connective tissue, and varies in thickness from a mere line to several. It was formerly called a pyogenic membrane, because the pus discharged was supposed to be formed by it. When such a limiting inflammation cannot take place, the abscess continually enlarges by the softening and destruction of the adjacent hepatic tissue, and may finally attain to enormous proportions. The embolic abscesses vary in size from that of a pea to that of an orange. The so-called tropical abscesses are usually single—in three-fourths of the cases, according to Rouis;93 in 62.1 per cent., according to Waring.94 Of the fatal cases collected by the latter author, 285 in number, a single abscess existed in 177, and multiple abscesses in 108. In 11 per cent. there were two abscesses; in 3.6 per cent., three; and in 5.6 per cent. there were four abscesses. As regards the part of the liver in which abscess occurs, the statistics show a great preponderance in favor of the right lobe. In Waring's collection of 300 cases the right lobe was the seat of the abscess in 163, or 67.3 per cent.; the left lobe was affected in 16, or 6.6 per cent.; and both lobes in 35, or 14.4 per cent. The preponderance of cases affecting the right lobe is the more striking when it is understood that, other parts being invaded, the right is included with them in the morbid process. In my own cases the right lobe was the seat of the abscess in 70 per cent.
93 Recherches sur les Suppurations endémiques du Foie, loc. cit., p. 146.
94 An Inquiry into the Statistics and Pathology, etc. connected with Abscess of the Liver, loc. cit., p. 125.