It is needless to enumerate all the concomitant symptoms of jaundice which will be better noticed under the different disorders which determine it, for a list of which see the causes.
The gravity of the affection will depend on the dangerous nature of these concurrent diseases, and the destructive changes in the liver and blood rather than on the depth of color in the textures.
CATARRHAL ICTERUS (JAUNDICE) OF SOLIPEDS.
Causes: infection from duodenum through biliary duct. Suppression of bile favors. Musty, heated, mow burnt fodder, over feeding, irregular feeding, or watering, over work, worms, fatigue, damp stables, duodenal congestion, gall-stones, concretions, pancreatic tumor, ascaris in bile ducts, distoma, infection through portal vein, toxins. Symptoms: of duodenal catarrh, icterus, yellow, viscous, odorous urine, dullness, weakness, somnolence, tardy pulse and breathing, costiveness, or diarrhœa, pale, fœtid stools. Duration: 2 to 3 weeks or longer. Lesions: duodenitis, distended biliary and pancreatic ducts, calculi, enlarged softened liver and kidneys. Diagnosis: icteric symptoms in absence of fever. Prognosis: usually favorable. Treatment: laxative diet, pasture, soiling, ensilage, roots, fruits, water freely, exercise, antisepsis, elimination, laxatives, cholagogues, diuretics, calomel, salines, nitro-muriatic acid, podophyllin, castor oil, aloes, tartar emetic, bitters, sodium bicarbonate.
Causes. This may be said to be an extension of infection from the duodenum through the bile ducts. The microbes of the intestinal canal become acclimatized by living in the bile-charged contents of the duodenum until they acquired the power of survival and multiplication in the biliary ducts themselves. The well known antiseptic qualities of the bile, constitute a powerful barrier to this, yet the power of adaptation on the part of certain germs is greater than the defensive action of the bile. The attack is however mostly in connection with indigestion or muco-enteritis, and a more or less perfect suspension of biliary secretion, so that this defensive action is reduced to its minimum and the germs can ascend the bile ducts in the mucous secretion as a culture medium, and by interference with the resumption of a free hepatic secretion, they succeed in safely colonizing themselves in the mucosa and hepatic parenchyma. Whatever, therefore, interferes with the integrity of the duodenal functions directly contributes to the extension of infection from bowel to liver. Old, heated, musty, cryptogamic, dusty fodder, grains that have been badly harvested in wet seasons, feed that has been damp and fermented, overloading of the stomach, irregular feeding and watering, giving drink after a feed of grain, underfeeding, overwork, worms, excessive fatigue, damp, dark stables, etc., tend to induce indigestions and to lay the bile ducts open to infection. Blocking of the bile duct and stasis of its contents may be a sufficient cause. The swollen mucosa around the orifice of the duct not only blocks the passage but favors the formation of a mucous plug as recorded by Benjamin of an equine patient. Wolff found obstruction of the duodenum in the horse by a mass of ingesta, and blocking of the gall duct, with jaundice.
Gall stones and concretions are very direct causes of biliary obstruction and jaundice. Though less common in horses than cattle, these are not unknown in idle, pampered animals when on dry winter feeding.
Tumors of the pancreas or adjacent organs pressing on the gall duct are recognized as causes of equine icterus, (Megnin, Nocard).
With any obstruction to the bile a disturbance of balance of pressure between the bile ducts and the hepatic veins is brought about by respiratory movements. On the one hand the aspiratory power of the chest empties the hepatic veins, lessening blood pressure, and in expiration the contraction of diaphragm and abdominal muscles compresses the gall ducts increasing their tension and favoring absorption of bile.
The entrance into the bile duct of the ascaris megalocephala is at once a cause of obstruction and of the transference of duodenal microbes, and the presence of trematodes (fasciola hepatica, or distoma lanceolatum) will also favor obstruction. Other parasites, like the echinococcus or actinomycosis, may press on the biliary ducts and determine jaundice.
Another mode of infection is by way of the portal vein, the microbes entering from the intestine and becoming arrested and colonized in the liver (Dieckerhoff).