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).
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.
A course of bitters, with bicarbonate of soda in small doses, may be
demanded to re-establish the healthy tone of the stomach and intestines,
and a run at pasture, or at least an open air life, exercise, and a
laxative diet with abundance of good water should be secured. Any undue
costiveness should be counteracted at once by a saline laxative.