CONGESTION OF THE LIVER IN THE HORSE.
Causes. Beside the general causes above mentioned, may be specially named, musty, decomposed, and irritant fodders: those which like green legumes, are easily fermented; and those which contain stimulating volatile oils or carminative principles. They are also especially exposed to such causes as severe and prolonged work under a hot sun, the nervous atony which causes vaso-dilatation in a hot climate, and such traumatisms as come from falls, kicks, goring, and blows by shafts, poles and clubs. These especially induce active congestion. The passive forms come mainly from obstruction in the lungs, or heart (dilatation, right valvular insufficiency, pericarditis, hydropericardium, myocarditis, fatty degeneration, endocarditis), or in the posterior vena cava.
Lesions. The congested liver is enlarged and deeply colored with blood. The weight of twenty to thirty pounds is often attained. While the color is of a deep red throughout, there are spots of a still darker hue indicating the seat of subcapsular or deeper seated hemorrhages. The color varies according as the congestion is passive or active. In the former the coloration is deeper in the centre of the acinus (nutmeg liver) indicating congestion of the hepatic veins, while in the latter the periphery of the acinus may be most deeply stained implying congestion of the portal vein. The consistency of the organ is diminished, and the more acute the attack the greater the friability. In such cases there is a parboiled appearance indicating granular and commencing fatty degeneration. Under the microscope the relative distension of the intralobular, and interlobular veins and the hepatic capillaries becomes more distinctly marked and the presence of pigment and fatty granules and the lack of protoplasm and nuclei in the hepatic cells indicate their progressive changes. When the peripheral cells are pale from fatty granules the contrast between the light margin and dark centre of the acinus, makes the mottled or nutmeg aspect of the liver much more pronounced.
In old standing cases of passive congestion the liver may be the seat of fibroid degeneration, extending from the capsule inward in bands or trabeculæ, and giving to the organ a firm resistant character (sclerosis, cirrhosis).
Symptoms. The symptoms are general and suggestive rather than pathognomonic. There are dullness, prostration, unsteady walk, pendent head, with occasional jerking, semi-closed eyes, redness of the conjunctiva, slight colicy pains, arching of the loins, muscular tremblings and decubitus on the left side rather than the right. The more definite symptoms are tenderness on percussion with the closed fist over the last ribs (the liver) especially on the right side, increase of the area of hepatic percussion dullness (which may be rendered valueless by a loaded colon), the presence of a slight icterus in the conjunctiva and urine, and an increase of the urine secreted and an excess of the contained urea.
In passive cases however the obstruction to the escape of blood from the liver prevents the development of icteric symptoms, of uræmia and of polyuria. In all such cases however there follows a general congestion of the portal system and if it persists for any length of time gastro-intestinal congestion and catarrh and even ascites may develop.
In all cases alike the history of the attack will help towards a satisfactory diagnosis.
Prevention. A rational hygiene embracing daily work or exercise, moderate laxative diet, green food in its season, pure cool air are important precautions.
Treatment. A moderate supply of green or laxative food, the withholding for the time of grain, and especially of maize, wheat or buckwheat, saline laxatives daily, and a stimulating embrocation or blister to the tender hypochondrium are the most important measures. Exercise in a box stall, or still better in a yard or paddock in the intervals between more systematic work forms an important adjunct to medicine. As a laxative sulphate of soda is to be preferred at first in a full cathartic dose and later in a daily amount sufficient to relax the bowels. Given in a bucket of water every morning before the first meal a very small dose will be effective.