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Jaundice in dogs
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Any dog can develop jaundice. It is
very unusual, however, to see jaundice in young puppies.
Dogs with jaundice have a yellow discoloration
of body tissues such as the eyes, gums, and skin. The
condition results from increased levels of bilirubin
in the body, which is one of the by-products of heme,
a red blood cell protein. Jaundice generally is not a
disease; rather it is a symptom of a number of canine
illnesses.
The causes of jaundice are classified as pre-hepatic, hepatic,
or post-hepatic in origin. Pre-hepatic jaundice occurs when
red blood cell breakdown, or hemolysis, produces bilirubin
faster than the liver can metabolize it. Hepatic jaundice
results from primary and secondary diseases within the liver
that interfere with the liver cells' ability to metabolize
bilirubin or excrete it normally into the biliary tract.
Post-hepatic jaundice can result from obstruction to the
flow of bilirubin-containing bile within the bile duct or
from injury that causes leakage from the gallbladder or bile
duct.
Once identified on physical examination, jaundice needs to
be assessed further to determine the type and cause. Bloodwork
is useful for measuring the bilirubin level and identifying
concurrent abnormalities. It will also help determine if
anemia is a factor in the affected dog's jaundice. If a pet
is not anemic, then the jaundice is likely to be due to liver
disease or to post-hepatic biliary abnormalities. Some patients
may have jaundice that has multiple causes.
The outlook for a jaundiced dog depends on the cause of
the jaundice. In general, jaundice is a significant and
serious sign, and the prognosis for most disorders causing
it is guarded, or uncertain. However, many diseases associated
with jaundice can be managed successfully with specific,
supportive therapy based on timely and accurate diagnostic
test results.
Jaundice is a clinical sign associated
with many diseases. Light-colored tissues will present
the characteristic yellowish discoloration of jaundice.
It is usually first recognized in the mucous membranes
in the mouth and in the eyes or skin. Additional signs
depend on the underlying cause of the jaundice in the
affected dog. In general, non-specific signs such as
lethargy, weakness, and reduced appetite will occur in
many dogs, although some jaundiced dogs are otherwise
asymptomatic. Many owners report the presence of dark
or discolored urine due to the presence of bilirubin
in the urine. Bilirubinuria may appear before the body
tissues are discolored.
Jaundice is a yellowish discoloration
of the skin, sclera -- the whites of the eyes -- and
mucous membranes of the mouth. It occurs when the amount
of bilirubin produced in the body exceeds the liver's
-- and to a lesser extent, the kidneys' -- ability to
excrete it. An elevated serum bilirubin level will also
result in bilirubin deposition in many other tissues
of the body. However, jaundice is not apparent in darker
tissues and internal organs. Jaundice becomes noticeable
when serum bilirubin reaches 2 mg/dl.
Bilirubin is an end product of heme metabolism. Heme is the
iron-containing component of hemoglobin, which is the molecule
in red blood cells responsible for carrying oxygen to the
body's tissues. Heme is also a component of myoglobin, which
resembles hemoglobin, and is present in muscle protein for
oxygen transport. When red blood cells break down, or hemolyze,
heme is separated from the other part of the hemoglobin molecule
and is metabolized to bilirubin. A small amount of bilirubin
in the blood is a normal consequence of the destruction of
old red blood cells. The normal wear and tear of muscle protein
also contributes to this normal level of serum bilirubin,
although not as much as red blood cell hemolysis produces.
Any disease process that produces excess bilirubin or interferes
with its metabolism and excretion from the body produces
the characteristic signs of jaundice. In dogs, there are
three basic classes of disease processes that cause jaundice:
pre-hepatic, hepatic, and post-hepatic. Pre-hepatic jaundice
is due to excessive red blood cell breakdown, or hemolysis,
which results in anemia and an abnormal increase in serum
bilirubin. Pre-hepatic jaundice may also occur when significant
muscle damage occurs. When muscles are significantly injured,
heme is released from myoglobin and is metabolized to bilirubin.
Hepatic jaundice is due to a disease or disorder located
within the liver. Such intra-hepatic disease may be primary
or secondary. Primary liver diseases originate in the liver;
secondary ones develop elsewhere in the body and then spread
to the liver or by other means cause disease within it. If
a jaundiced dog is not anemic and if there is no evidence
of bile duct obstruction or gallbladder disease on x-ray
and ultrasound studies, then intra- hepatic disease is likely.
A number of mechanisms underlie the development of hyperbilirubinemia
associated with liver disease, both primary and secondary.
Necrosis, or death, of liver cells will impair the liver's
functional capacity to store and metabolize bilirubin. The
formation of scar tissue in the liver in response to injurious
agents can cause obstruction of bile flow within the liver,
thus preventing its excretion. Compression of the intrahepatic
duct system by tumors can block the flow of bilirubin-containing
bile flow also. Inflammatory conditions of the liver can
cause intrahepatic congestion that can block the flow of
bile through the liver as well.
Post-hepatic jaundice occurs with bile duct obstruction
or biliary tract leakage. Normally bile is eliminated in
the gastrointestinal tract. When this normal elimination
of bilirubin is impaired, serum concentrations of bilirubin
will rise. Obstruction to bile flow outside the liver will
cause secondary bile flow obstruction in the liver. When
post-hepatic bile flow is obstructed, leakage of bile from
the obstructed biliary tract into the abdominal cavity
can readily occur. The bile, including bilirubin, will
be absorbed through the abdominal cavity wall and enter
the blood stream.
A persistently high level of serum bilirubin, as evidenced
by jaundice, can have secondary toxic effects on various
tissues, including the kidney and liver. A pre-hepatic
or post-hepatic disease process associated with hyperbilirubinemia
could result in secondary hepatic toxicosis that could
further impair the affected dog's ability to process bilirubin.
The diagnosis of jaundice usually
is based on the yellow discoloration of the skin or mucous
membranes noted by the veterinarian upon physical examination.
Bloodwork will document elevation of the serum bilirubin
concentration, which in dogs is normally less than 1.0
mg/dl. Urinalysis will demonstrate an abnormal amount
of bilirubin in the urine as well. Although elevated
levels of bilirubin may be present in the blood and urine,
jaundice may not become clinically evident until the
serum bilirubin level reaches 2.0 mg/dl.
When jaundice is noted, additional tests will be needed to
determine its cause. A complete blood count, or, at the very
least, measurement of the packed cell volume, is typically
done to rule out anemia. If anemia is present, then the jaundice
may be due to red blood cell breakdown, a condition known
as hemolysis, and additional tests will be needed to look
for the cause of the anemia.
Jaundiced dogs that are not anemic most likely have liver
or post-hepatic biliary tract disorders. A blood chemistry
profile provides confirmation of elevated total serum bilirubin
concentrations, and documentation of liver enzyme, serum
electrolyte, and glucose levels and kidney function values.
Urinalysis is important to confirm the presence of bilirubin
in the urine. Small amounts of bilirubin can be found in
the urine of many normal dogs, but large amounts are abnormal.
Minor serum bilirubin elevations unaccompanied by jaundice
or the presence of bilirubin in the urine may be incidental
findings related to blood sample collection technique or
recent ingestion of food, and therefore may not be significant.
Imaging studies provide important information in the diagnosis
of hepatic and post-hepatic causes of jaundice. Abdominal
radiographs, or x-rays, are routinely performed to assess
liver size and to look for evidence of stones in the biliary
tract. Abdominal ultrasound is the most readily available
non-invasive diagnostic tool used to detect bile duct obstruction
or primary gallbladder abnormalities not otherwise revealed
by conventional radiographs. Ultrasound can also be used
to guide needle biopsy of the liver. A liver biopsy provides
tissue for microscopic detection of liver tissue abnormalities.
This is typically done if anemia is not present and there
is no evidence on ultrasound examination of bile duct obstruction
or gallbladder disease. When the ultrasound study reveals
obstruction, exploratory surgery is often necessary to identify
and correct the obstruction's cause. Such surgery is also
performed when a cause for the jaundice remains unclear after
other diagnostic tests and procedures have been performed.
As with all disease signs, the outcome
in a jaundiced dog depends primarily on the underlying
cause of the jaundice and on the animal's response to
treatment. Dogs with pre-hepatic jaundice due to hemolysis
may recover completely if their respective diseases are
identified and treated successfully. However, the mortality
rate for patients with pre-hepatic jaundice can also
be quite high, as many dogs succumb to their underlying
diseases.
Patients with jaundice due to primary liver disease may recover
completely, especially if the problem was drug or toxin related.
Prognosis in these cases is good if further exposure to the
drug or toxin is avoided and supportive care is provided
as necessary. Some types of liver disease, particularly chronic
hepatitis and cirrhosis, follow a chronic course, characterized
by relatively quiescent periods interspersed with periods
of more active disease. Jaundice may come and go in these
patients. Many veterinarians used to think that the presence
of jaundice in a dog invariably signaled a fatal illness.
Today, however, the outcome may be more favorable for many
affected dogs when treatment is given based on the results
of accurate and appropriate diagnostic tests.
Patients with post-hepatic jaundice often have resolution
of the jaundice after the obstruction is relieved or once
the leaking part of the biliary tract is repaired or removed.
Nevertheless, the long-term outlook depends more on the cause
of the obstruction or bile duct injury. Patients with traumatic
injury to the gallbladder or bile duct, or obstruction due
to stones, may do well indefinitely once the problem is addressed,
but dogs with bile duct or gallbladder cancer usually do
not survive for long periods of time. In dogs with bile duct
obstruction secondary to pancreatitis, the prognosis is best
if the obstruction resolves without surgical intervention.
Some dogs that require surgical intervention and re-routing
procedures to establish normal bile flow also do quite well,
but others experience chronic problems with infection, inflammation,
or progressive liver disease once surgery is completed.
There are many different diseases
that can cause jaundice in dogs. These are pathophysiologically
classified as pre-hepatic, hepatic, and post-hepatic,
depending on the anatomic/functional location of the
underlying disease process.
There are many pre-hepatic causes of jaundice, most of which
are associated with hemolysis of red blood cells and the
anemia that results. These include toxins and certain drugs,
severe heartworm disease, red blood cell parasites and other
infectious diseases such as ehrlichiosis and leptospirosis.
Immune-mediated red blood cell-destructive diseases, such
as autoimmune hemolytic anemia and systemic lupus erythematosus,
inherited red blood cell enzyme abnormalities and cancer
also may produce profound jaundice. Non-hemolytic disorders
of muscle, including trauma and certain muscle degenerative
diseases can also cause pre-hepatic jaundice.
Various liver diseases that interfere with the liver's role
in controlling bilirubin levels can cause hepatic jaundice.
Exposure to certain toxins and drugs can cause liver cell
necrosis and hepatic dysfunction. Anti-seizure drugs, such
as phenobarbital and phenytoin, acetaminophen, sulfa-type
antibiotics, and mebendazole, an anti-parasitic medication,
are some of the drugs commonly prescribed for dogs that can
cause hepatic jaundice. Various liver cancers -- both arising
in the liver as well as metastasizing, or spreading, to it
-- may cause intra-hepatic obstruction to bilirubin excretion
and jaundice. Inflammatory disorders such as chronic active
hepatitis and cholangitis, and infectious liver diseases
of bacterial, viral or fungal origin often produce jaundice
in the early stages of the disease process. Cirrhosis, where
the functional tissue of the liver becomes scarred due to
a number of disorders, produces hepatic jaundice in severe
cases. Congenital or breed-related genetic liver diseases
in Bedlington terriers, Doberman pinschers and some other
breeds may also be associated with hepatic jaundice.
Post-hepatic jaundice occurs when the common hepatic duct
or the bile duct becomes obstructed or when bile leaks from
any point along the biliary tract, including the gallbladder.
Possible causes of duct obstruction include pancreatitis,
gallstones, and cancer. Traumatic injury to the gallbladder
or bile duct can lead to obstructing blood clots or structural
damage. Spontaneous rupture of the bile duct or gallbladder
can result in leakage of bile into the abdomen. Such ruptures
often occur as a result of a long-standing obstruction.
There is no specific treatment for
jaundice. The main goal is to identify the cause of the
jaundice and to treat it as specifically as possible.
If the jaundice is due to excessive hemolysis, the cause
of the hemolysis dictates its treatment. Any potential
toxins that can cause hemolysis should be identified
and removed, and further exposure should be prevented.
Antibiotics or anti-parasitic agents may be needed for
infectious or parasitic causes of hemolysis. Immune system-suppressing
drugs such as corticosteroids are used to treat immune-mediated
hemolysis. Blood transfusions may be needed to treat
anemia symptomatically until its cause is identified,
or to allow time for other medical treatments to work.
When jaundice is caused by a primary or secondary liver disease,
treatment is directed at the underlying disorder. Some liver
diseases respond to specific treatments, while the majority
can only be managed symptomatically and supportively. Treatment
of liver disease in dogs may include fluid administration,
antibiotics, antacids, anti-inflammatory drugs, vitamin K,
drugs to suppress scar tissue formation or to influence bile
flow, and vitamin E and fatty acid supplements. Some liver
diseases resolve with time, but many, such as chronic hepatitis
and cirrhosis, do not resolve and may progress with time.
Nevertheless, treatment is frequently helpful in managing
patients during the active stages of the disease and in improving
the quality of life between episodes.
Bile duct obstruction or leakage, or primary gallbladder
diseases identified on ultrasound usually require surgery.
One exception is bile duct obstruction secondary to pancreatitis,
which may resolve with time and without surgical intervention.
There are no specific means of prevention
for most disorders that cause jaundice in dogs. Routine
vaccinations protect against infectious hepatitis caused
by adenovirus and Leptospira species of bacteria.
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