Testing and Diagnosis of Canine Liver Disease
A thorough approach is needed for a correct diagnosis of any liver problem. An organ like the liver that
is so intimately involved with other important organs will exhibit symptoms that mimic disease in these other organs. Also, what initially might appear as a diseased liver is in reality a disease elsewhere in the
body that is involved with the liver secondarily. This is why it is crucial to follow a thorough and methodical approach called the diagnostic process.
Specifically noting signs which may indicate liver disease. Periodic ascites, intolerance of a high protein diet, icterus, chronic weight loss, abnormally colored feces or urine, bleeding disorders, chronic illness, and all that has been mentioned above. Sometimes urinary crystals formed from the improperly metabolized proteins and amino acids may indicate liver disease.
Liver disease can occur in pets of any age. If it occurs in young animals we tend to think more of toxicity, a liver shunt or a viral disease like adenovirus in dogs. In older pets we tend to think more of inflammation and cancer as the cause of the liver problem.
Several canine breeds are prone to getting liver disease:
Bedlington terriers, Skye terriers, Doberman pinschers, and West Highland White terriers get a
problem with excessive copper accumulation that results from failure of normal biliary excretion of copper. Cocker spaniels have an increased incidence of chronic hepatitis
Early signs of liver disease are subtle, and might exhibit as some of the symptoms described above. It is important to remember that some pets do not show any symptoms early in the course of the disease. This is another reason for yearly exams, along with blood and urine samples in dogs and cats 8 years of age or more. Even though many cancers do not show up in a blood sample, we can sometimes get indirect evidence there is a problem, leading to additional diagnostic tests that might find cancer.
The recent use of pesticides, insecticides, and drugs might give us a clue. Some Labradors are sensitive to the use of the arthritis medicine Rimadyl. These dogs should have a blood panel analyzed prior to initiating Rimadyl therapy. Every 6 months this panel should be repeated.
A history of poorly controlled diabetes mellitus might also clue us in to liver problems. Pets with
liver shunts might have stunted growth and become depressed right after eating.
Routine physical exam findings might include:
Distended abdomen due to enlargement of the liver (hepatomegaly) might be found. This can be palpated in some situations, especially in the smaller animals. an enlarged liver from a disease other than liver disease can cause hepatomegaly. This includes heart disease and Cushing’s Disease.
Enlarged lymph nodes due to secondary bacterial infections or spread of a primary or metastatic
Bruising (hematoma) might be observed under the skin, or when a blood sample is obtained. This is
due to the liver’s affects on the clotting mechanism
Fever- a rectal temperature of greater than 103 degrees F could accompany liver disease when inflammation or infection is present
Skin infections and wounds that do not heal, or recur after antibiotics are stopped
Yellowish discoloration (icterus or jaundice) of the ears, gums, or hairless areas of the skin
Anemia might be observed by checking the mucous membranes for a normal pink color
Extensive Blood Work and Diagnostic Testing
A complete blood count to check for anemia and blood cell abnormalities. A CBC (complete blood
count) and BCP (biochemistry panel) should be run on every pet 8 years of age or more, especially if they have any of the symptoms of liver disease. The CBC might show a decrease in the number of red blood cells (RBC’s). This decrease in RBC’s is called anemia. The white blood cell count (WBC) might be elevated (leukocytosis), normal, or decreased (leukopenia), mostly depending on the cause of the liver problem and how long it has been present. A change in the WBC’s does not necessarily indicate there is a liver problem.
A complete chemistry screen, including ALT, ALP, AST, bilirubin, glucose, urea, electrolyte levels,
albumin, globulin and bile acid levels. The bile acid levels should be checked on an empty stomach and two hours after feeding. All these values, with the exception of the bile acids, usually are included on
a standard Small Animal Data Base Screen.
Important Liver Enzymes
Traditionally the medical practitioner has measured the relative concentration of several enzymes which may indicate alterations in liver health. The following enzymes typically change values in the face of liver failure
Alanine Aminotransferase: ALT – Liver specific. Cell damage will cause elevations of ALT due to leakage. The elevation of the enzyme correlates with the number of cells damaged. Falling levels of ALT may indicate recovery or may indicate a failing number of functional liver cells. Rapid increases in ALT may indicate an acute process, while slow increases may indicate bile duct obstruction.
Normal Test Range: 10-100 U/L*
Aspartate Aminotransferase: AST - an enzyme seen in the liver, heart, kidney, skeletal muscle and brain. The half life of the AST in the blood stream is much shorter than that of ALT, therefore the values of AST tend to drop more rapidly once liver function is resumed. AST elevations and ALT elevations should parallel each other in liver disease
Normal Test Range: 5-55 U/L*
Alkaline Phosphatase: ALKP/ALP – This enzyme is present in many tissues, therefore it not very specific in liver disease, but it appears very early in the progress of liver disease, therefore it is considered quite sensitive. ALP tends to be slightly more specific in the cat, but not quite as sensitive. A similar enzyme or isoenzyme is secreted as a result of high levels of cortisone, therefore an effort must be made to separate Cortisole induced ALP or CALP and normal ALP. Liver ALP is released from the liver when many anticonvulsant drugs are administered to the dog. This must be taken into account when evaluating ALP levels. ALP levels typically are greatly elevated in the young, growing animal and therefore a veterinarian should not mistake any elevations as disease in a young animal.
Normal Test Range: 23-212 U/L*
Gamma Glutamyltransferase: GGT – This enzyme is has its highest concentration in the kidneys and pancreas, but it is also found in the liver and other organs. The major proportion of GGT in the serum seems to come from the liver. Elevations of GGT in disease seem to stem from new synthesis rather than leakage, therefore the changes seen due to disease are not spectacular. Large elevations of GGT are more commonly associated with pancreatitis and bile duct obstruction.
These series of organic acids circulate almost entirely in the localized blood flow between the intestines
and the liver (a.k.a. the Portal system). The flow is typically from the liver, into the bile duct system, then excretion into the intestines to aid digestion after a meal, to be re- absorbed into the portal system and recycled by the liver. Very little of the bile acids escape from the portal circulation system into the rest of the body. Leakage is considered abnormal and is a sure sign of a liver abnormality. This is one of the most sensitive tests available to diagnose liver disease. While the liver does actually manufacture this product, it has tremendous reserve capacity and can easily meet the bodies demand for bile acids despite severe disease. As a result of this reserve, the bile acid levels do not typically drop due to liver disease.
Normal Test Range: Pre = Less than 7.0 umol/L, Post = Less than 15.0umol/L*
A complete urine analysis
Check urobilinogen levels, bilirubin levels, glucose levels, protein levels. Again all this is usually on a standard urinalysis panel.
Radiograph the abdomen
X rays can show increased liver size, decreased liver size liver abscesses, abnormal mineralization , and circulatory abnormalities (using special dyes).
Ultrasound the liver
Perfect technique for visualizing the circulation of the liver, the bile duct system, the density of the liver tissue, the size of the liver. Ultrasound is highly beneficial in the diagnosis of liver disease. We recommend ultrasounding a liver when the liver enzymes tests are elevated over time, or the bile acids test is abnormal. The internal structure (called parenchyma) can be analyzed, and post-hepatic liver disease can be differentiated from hepatic liver disease. This can be very important because disease in the liver can often be diagnosed with a biopsy during the ultrasound. Post-hepatic liver disease cannot easily be diagnosed in this matter. Instead it is diagnosed and treated with an exploratory surgery (called a laparotomy).
Biopsy of the liver
While this is a surgical technique, it is the ultimate for diagnosis, since it allows us to directly examine and test liver tissue, give an absolute diagnosis and hopefully a final treatment regime. Biopsies can be taken by full laparotomy, where the surgeon actually looks at the liver and removes a small piece, or they can be done by a biopsy needle guided by ultrasound through the body wall. The liver will regenerate any piece that has been removed, therefore liver biopsy is usually a low risk procedure in capable hands.
*The ranges for the test results listed above are dependent on the lab, the testing done and are relative. Some specialist allow for a much larger range before they diagnose “true” Liver Disease. After receiving your test results, please consult with an internal specialist and have them explain the results to you.