L I VER D I SEASE
SPRING 2015 ISSUE
EQUINE MATTERS
10
Prevention
Although it may not be possible to
prevent liver disease in all cases,
avoiding over grazing of pasture
and identifying and removing toxic
plants as soon as possible will help.
In addition, regular blood samples
in older horses or those on long
term medication will help detect
liver disease early when treatment
may be more successful.
Diagnosis
As liver disease can manifest in different ways, diagnosis based on history and clinical signs alone is not
normally possible, however certain combinations of signs may raise suspicion of liver involvement. The
following diagnostic tests are commonly used both to diagnose liver disease and to help determine the
cause, extent, severity and prognosis of the disease.
Treatment
Treatment depends on the cause, type and
severity of the disease and is therefore
often guided by liver biopsy results. In
many cases, treatment with antibiotics,
non-steroidal anti-inflammatory drugs or
corticosteroids may be indicated, either
alone or in combination.
In cases where the signs of liver failure are
already apparent, intravenous fluids and
lactulose may be added to the treatment
regime in order to try to flush the toxins out
of the horse’s system.
Vitamin supplementation is often necessary
to prevent deficiencies developing.
In addition, milk thistle
(Silybum
marianum)
has been shown to have a
protective effect on the liver in humans,
and is thought to be beneficial in horses.
Avoiding diets with high protein content is
recommended, and in cases of fatty liver
disease it is vital to provide high energy
rations and encourage eating as soon
as possible.
Liver biopsy site:
Liver biopsy is considered the 'gold
standard' in the diagnosis of liver disease.
A biopsy can provide information about
the cause, best treatment options and
prognosis of the disease.
The procedure involves inserting a special
biopsy needle through the body wall and
into the liver to obtain a thin strip of liver
tissue. This process is then repeated until
several samples have been obtained.
These tissue samples are then examined
under a microscope to determine the type
and extent of disease. If an infectious
cause is suspected then a bacterial culture
may also be performed.
The procedure is performed with the horse
sedated and local anaesthetic injected into
the skin and muscle layers overlying the
biopsy site. Staples or sutures may be used
to close the skin layer afterwards. In some
cases a blood sample may be taken
before the procedure to check that your
horse’s blood is clotting properly.
Blood work:
Ultrasonography:
Damaged liver cells release enzymes into
the bloodstream, which can be easily
detected in a blood sample. However,
some enzymes are also released by other
organs in the body so careful interpretation
is required, and although blood samples
can indicate liver damage they do not give
any indication as to the cause. Bile acid
levels can also be easily measured -
increased bile acids indicate impaired liver
function, and occur when the liver is
already starting to fail. Infection and
inflammation may also be detected, but
again it is not possible to identify a cause.
An ultrasound examination can give
information about the size of the liver (for
example smaller or larger than normal),
as well as assess the liver tissue for bile
duct obstructions, fibrosis or abscesses. In
addition, it can be used as a guide for
liver biopsy. This type of examination is
straightforward, non-invasive and usually
well tolerated. Your horse may require
extensive clipping (especially if he is a
hairier type!) on both sides of his chest, and
may require light sedation to keep him still.
Causes of liver disease
Toxins, infections, inflammation, parasites,
drugs (both naturally occurring and
synthetic), starvation and neoplasia can
all cause liver disease to varying degrees.
Plant toxicity is one of the most common
causes of liver damage. Plants containing
pyrrolizidine alkaloids, such as ragwort
(Senecio jacobea)
, are particularly toxic
and even small amounts can cause
irreversible liver damage. Other toxins
include mycotoxins and aflatoxins, which
can be found in mouldy grains, and iron.
Liver infection most commonly occurs via
the intestinal tract. Bacteria may form
abscesses or infect the bile ducts and
surrounding liver tissue. Inflammation can
be primary, or can occur secondary to
another cause of liver damage.
Many drugs are processed by the liver.
Whilst these drugs may not cause direct
liver damage, impaired liver function
may affect their usefulness.
Fatty liver disease is a serious condition,
usually affecting obese animals. It can
occur when there is a sudden decrease
in food intake or increased energy
demand such as during pregnancy.
The resulting negative energy balance
results in fats being released from stores
in the body, which accumulate in the
liver and cause impaired liver function
.
Liver damage:
