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Name
Jaundice, Canine
Short Description
Jaundice, icterus, hyperbilirubinemia
Affected Animals: Any dog can develop jaundice. It is very unusual,
however, to see jaundice in young puppies.
Overview: 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.
Clinical Signs: 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.
Symptoms:
See Clinical Signs.
Description: 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.
Diagnosis: 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.
Prognosis: 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.
Transmission or Cause: 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.
Treatment: 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.
Prevention: 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.
