The influence of climate, especially of long-continued high temperature, has been warmly disputed. On the whole, it seems probable that in warm climates congestion of the liver is much more common. Malarial infection is an unquestionable cause. In the section on Jaundice it was stated that this symptom may occur without the phenomena of fever, and, indeed, without any other disturbance of the system. In a large proportion of cases of intermittent fever, probably in all, more or less congestion of the liver occurs.
PATHOLOGICAL ANATOMY.—Congestion may take place in the portal system, and be due to conditions of the gastro-intestinal mucous membrane, or in the hepatic vein and radicles, due to obstructive troubles in the heart or lungs. The appearances vary accordingly. Restricting the observations to the hyperæmia, and not including subsequent lesions, it suffices to say that the liver is somewhat enlarged, rather darker in color than the normal, and uniformly so; the radicles and branches of the portal vein in the liver, the trunk of the vein itself, and the veins of the spleen, stomach, intestines, mesentery, etc. are distended with black blood, and the tissue of the liver rather wet, inclined to soften, and here and there marked by minute hemorrhages from rupture of small vessels. The extravasations of blood accompany the hepatic congestion of hot climates, and probably are the preludes to suppurative inflammation. The portal system the more readily suffers from a passive congestion because of the provision for the alternate expansion and contraction of the tunics of the vessel, scantily supplied with contractile elements. An acute congestion of the liver produced by sudden dilatation of the capillaries of the hepatic artery has not been described, but it would appear to be possible.
The most important form of hepatic congestion is the mechanical, arising from obstruction of the circulation in the heart or lungs. In consequence of this obstruction the blood accumulates on the venous side, and there is in consequence an ischæmia of the arterial side. The hepatic vein becomes distended, and its terminal radicle in the centre of each acinus—the central vein—enlarges with the increased pressure. It follows that the minute capillaries emptying into the central vein are also distended with blood, and finally the portal vein and its radicles throughout are similarly affected. The same condition of the hepatic circulation was long ago observed by Virchow41 as a result of weakness of the muscular tissue of the heart, and consequently diminished propelling power of the organ. On section of the liver much black blood flows out; each central vein is a distinct dark object in the centre of each acinus, and contrasts strongly with the surrounding paler substance, whence the common term for this appearance is nutmeg liver. The long-continued distension of the central vein leads to sclerosis of its walls,42 and the neighboring hepatic cells undergo atrophy in consequence of the greater pressure. A relatively increased quantity of connective tissue seems to result, but whether hyperplasia occurs is disputed. By Talamon43 such increase of the connective tissue is denied, but Thierfelder44 admits that there is an apparent and also in some cases a real increase. The atrophy of the cells induces more or less shrinking and consolidation of the liver; it is therefore smaller in size and firmer in texture, and presents a brownish-red color. The atrophic change in the hepatic cells is represented finally by some brownish or black pigment, but it is rare, indeed, for all the cells of an acinus to disappear. To this change has been applied the term cyanotic atrophy. In some instances Liebermeister45 has found an increase of the connective tissue of the liver; and this opinion is confirmed by Legg.46 When this multiplication of the connective tissue occurs, the condition of the liver is entitled cyanotic induration. The sclerosis originating in this way is distinguished from true cirrhosis by its less extent, irregularity, situation, and the marked degree of hepatic congestion.
41 Archiv für path. Anat., etc., Band v. p. 289.
42 Talamon, Recherches anatomo-pathologiques et cliniques sur le Foie cardiaque, Paris, 1881 (pamphlet).
43 Ibid.
44 Atlas.
45 Beiträge zur path. Anat. u. Klinik der Leberkrankheiten, Tubingen, 1864, p. 209 et seq.
46 Medico-Chirurgical Transactions, vol. lviii. p. 345.
SYMPTOMS.—Hyperæmia of the liver is usually one of the complex conditions of a morbid state, and hence is associated in its symptomatology with the connected maladies. On the one hand associated with gastro-intestinal disorders, on the other with cardiac and pulmonary diseases, the symptoms must be varied accordingly. It is necessary, however, to indicate as clearly as may be those belonging to the hepatic circulation.