Whether from the presence of the microbes or from the absorption of ptomaines and toxins from the intestines, the radical biliary ducts become inflamed, swollen, and even blocked, and the hepatic cells degenerated or even completely devitalized, so that they fail to take an aniline stain. In such cases the remaining sound hepatic cells go on producing bile, but as this cannot any longer escape through the partially obstructed interlobular biliary radicles, it is largely absorbed and produces icterus. Cadeac mentions a case of this kind in a mare in which the toxic matters had not only led to hepatic disease, but also to structural changes in the eliminating organ (the kidney).
Symptoms. In the horse the disease is mostly attendant on subacute duodenitis, and even when this is associated with infective catarrh of the biliary passages the kidneys remain mostly sound and active, and eliminate alike the bile pigments and the more toxic matters so that the disease is not often grave. Beside the essential feature of yellow mucosæ, and urine, the latter viscous and smelling strongly, there is profound depression, sluggishness, weakness and somnolence. Imperfect muscular control and even slight paresis may be present. Tardy pulse and breathing are at times noticeable. At others these, like the temperature, are normal. The mouth is hot and dry. The urine may be slightly albuminous. The bowels incline to costiveness from lack of their customary stimulus, yet this in turn may give rise to diarrhœa. In either case, as the disease advances, the defecations lose the healthy yellowish brown color, becoming pale and fœtid.
Duration. The attack may last one, two or three weeks, and generally ends in recovery. With irremediable structural lesions, it is of course permanent and even fatal.
Lesions. The most common feature is duodenitis with thickening around the orifice of the common bile and pancreatic duct. The biliary ducts may be distended and their contents more than usually viscid and glairy from the presence of pus. Their mucosa may show ramified redness, or concretions as casts or calculi. The liver is enlarged, soft and friable giving way readily under the pressure of the finger. Enlargement of the kidneys is usually present, the cortical substance having a brownish red and the medullary portion a yellowish pink hue.
Diagnosis. The absence of hyperthermia in jaundice, serves to distinguish it from the acute febrile affections (pneumonia, influenza, contagious pneumonia, petechial fever, etc.,) which are marked by yellowness of the mucosæ and skin.
Prognosis. The merely functional forms of icterus in solipeds usually end in recovery.
Treatment. The first consideration is a laxative diet. A run at pasture will usually meet every indication. Fresh cut grass, ensilage, turnips, carrots, potatoes, beet, apples, or other succulent diet may be given as substitute. Bran mashes and hay cut and moistened may be allowed in the absence of the above. Abundance of water and especially cool water will stimulate bowels, liver and kidneys, favor the elimination of the bile by contraction of the biliary ducts, and hasten the expulsion of the poisons through the kidneys. Regular exercise an hour after meals stimulates both bowels and liver to action.
Medicinal treatment is largely directed to antisepsis of the bowels and the arrest of the production of injurious toxins; elimination from the bowels and incidental depletion from the portal vein and liver; antisepsis and stimulation of the liver; and stimulation of the urinary secretion.
The preparations of mercury fill several of these indications. Calomel 2 drs., or blue mass 1½ dr., is not only a soothing laxative and antiseptic, but seems to operate as a calmative and antiseptic to the liver as well. It may be continued in 5 to 10 grain doses two or three times a day, according to the size of the animal and the condition of the bowels, and associated with ½ dr. belladonna extract to each dose together with a bitter (quassia, gentian, nux vomica). Or 4 or 5 ozs. sulphate of soda may be given three times a day, with 2 drs. salicylate of soda as an antiseptic. Or, to increase the hepatic action, nitro-muriatic acid largely diluted may be given in sixty drop doses thrice a day in the drinking water. These are especially valuable for their antiseptic action, cutting off at once the source of nervous irritation from the attendant indigestions, and duodenal congestion, and arresting the flow of the irritant toxins and other products through the portal system. Podophyllin, castor oil, aloes, rhubarb, often act well by depletion from the portal vein, and expulsion of indigestible and irritant matters from the intestines, but there is more danger of resulting swelling of the duodenal mucosa than with the mercurials or aqua regia. Goubaux recommends 2½ drs. of tartar emetic.
Siedamgrotzky has had good results from an electric current sent through the region of the liver, but in the horse this is rarely demanded.