The presence of oil globules in the liver cells is normal and
physiological, the liver acting to a certain extent as a store-house for
fat. This is always a marked feature, in healthy animals on high
rations, and taking little or no work, but so long as the protoplasm and
nuclei of the cells retain the normal characters and functions the
condition is not a morbid one. It may, however, become excessive, with
great enlargement of the liver, and with the substitution of fatty
granules for the protoplasm of the cells as in ducks and geese subjected
to forced feeding, and the condition becomes a distinctly pathological
one.
In true fatty degeneration the protoplasm of the hepatic cells is
destroyed and replaced by fatty granules, the resulting condition being
a permanent destruction of the cell for physiological uses.
_Causes._ The liver cells undergo fatty degeneration under the action of
certain poisons like phosphorus, arsenic, antimony, lead, phenol,
iodoform and alcohol. According to Neyraud oxide of antimony is given
daily to fattening geese to hasten the development of fatty liver.
An excess of fatty elements in the food leads to the same result as
shown first by Majendie in dogs, in which not only did the liver undergo
this degeneration but the sebaceous glands of the skin secreted an
excess of volatile fatty acids.
The cryptogams and their products on musty fodders determine a
gastro-enteritis in herbivora, accompanied by fatty degeneration of the
liver.
Colchicum Autumnale, and poisonous yellow lupin both determine this
degeneration.
The products of a number of pathogenic bacteria have a similar effect.
This has been noticed in the cat with bacillus pyocyaneus (Charrin), the
cholera spirillum, pyæmic and septicæmic infection, contagious pneumonia
of the horse, strangles, and ulcerative endocarditis. It has been long
noticed to be a complication of pulmonary tuberculosis, the result in
this as in other affections of the lungs having been attributed to
lessened oxidation in the tissues. It occurs also in hæmorrhages,
ruptures and inflammations of the liver and in passive congestions of
the organ, the impairment of the normal functions (in the altered
conditions of nutrition, or under the influence of poisons,) proving an
important factor in the process. The same remark may apply to the fatty
degeneration which complicates most other liver diseases, cirrhosis,
catarrh of the bile ducts, distomatosis, echinococcus, carcinoma, and
epithelioma.
Certain other factors must be taken into account. The inherited
disposition to the production of fat which characterizes the improved
breeds of butcher animals, and particular individuals of all breeds,
mature age which predisposes to the deposit of fat in internal organs,
old age which lessens the vitality of the cells, and hot, damp climates
or stables, all operate more or less in determining the fatty change.
_Lesions._ In fatty degeneration the liver is enlarged, pale, bloodless,
yellowish, its cut surface exudes an oily fluid which smears the knife,
and it is so light that it floats on water. If scraped and the material
drawn across a sheet of paper it forms a transparent oily stain. Under
the microscope the liver cells are seen to be enlarged and to have their
protoplasm and nuclei replaced by fat or oil. If due to obstruction in
the heart or lungs the degeneration is greatest toward the centre of the
acinus, if due to an infectious disease it is usually greatest towards
its periphery. In infectious diseases too the liver is not pale yellow,
but usually of a deep brownish or yellowish red. The degeneration may be
local or general. McFadyean found a circumscribed lesion in an ox’s
liver, of a bright ochreous color, and the cells completely transformed
into fat cells, while the rest of the liver was sound. In the dog fatty
areas, up to an inch in diameter, are not uncommon. The swollen cells
pressing on the adjacent vessels, account for the bloodless condition,
and favor the degenerative process.
Neyraud records a fatty liver of 28 ℔s. weight from the horse, and Kitt
one of 10 ℔s. from the pig.
_Symptoms._ Like as in most chronic liver diseases the indications are
uncertain. The conditions may, however, suggest fatty degeneration; if
the patient is very obese; if it has had an abundant food, rich in
hydrocarbons and carbohydrates, and little exercise; if it has received
in food or water continuous doses of phosphorus, arsenic or antimony; if
it has lived in a hot moist climate or stable; if there has been a
tendency to costiveness and indigestion; if the patient is weak, easily
fatigued and short-winded; if there is a slightly yellowish red tinge of
the conjunctiva and if the urine is scanty and contains little urea. If
the disease is more advanced and the animal emaciated, it may be
possible in the smaller animals at least to manipulate the liver to make
out its increase, its smooth surface, and its absence of tenderness.
_Treatment._ When met with in meat producing animals the best resort is
to turn these over to the butcher. When in an animal which is mainly
valuable for breeding purposes, or in horses or carnivora, something may
be done to check the progress of the malady, and maintain at least the
present condition. The value of this will of course depend on how far
the disease has already progressed. Cows that have spent a winter in a
hot swill stable are of little use afterward for breeding or dairy uses
and advanced cases of fatty degeneration in the horse or dog hold out
little hope of a satisfactory issue. For cases in the earlier stages,
nothing can be better than a run at grass, where there is opportunity
for shelter from the noonday sun. If the pasture is short and the animal
has to exercise to secure a living, so much the better. If kept indoors
the patient should have a clean, roomy airy box stall, with a moderate
allowance of easily digested food, and laxatives and cholagogues daily
such as Glauber salts, aloes, calomel, podophyllin or cream of tartar.
Mineral acids, especially nitro-muriatic acid, and bitters may also be
given. The preparations of iron are sometimes useful in maintaining the
tone of the digestive organs and counteracting anæmia but they must be
conjoined with diuretic doses of bicarbonate of soda.
There is great advantage in stimulating the skin, and active brushing,
currying, hand-rubbing, and even cold douches may be resorted to.