If your dog shows signs of liver disease, your vet will do blood tests to aid in making a diagnosis. One of things he or she will look for in the blood tests is dog liver enzymes which will be elevated in dogs with liver disease.
Dog Liver Enzymes
There are several enzymes your veterinarian will be looking for:
- Alanine Aminotransferase (ALT): ALT is a liver-specific
enzyme, meaning it is not found elsewhere in the body. Increases are
not considered abnormal unless they are two to three times above normal,
and even then, they can be caused by many things besides liver disease.
For instance, inflammatory gastrointestinal disease, cardiac failure, and the abnormal breakdown of red blood cells (hemolytic anemia) can all cause elevated ALT levels, as high as four to five times normal levels.
However, an increase in ALT along with other liver enzymes is an indication of liver disease. Cell damage will cause elevations of ALT due to leakage. The elevation of the enzyme correlates with the number of cells damaged. Decreasing levels of ALT may indicate recovery or may indicate a falling number of functional liver cells.
- Aspartate Aminotransferase (AST):
AST is an enzyme found in the liver, heart, kidneys, skeletal muscle,
and brain. The half-life of AST in the blood stream is much shorter than
that of ALT, meaning that levels in the blood decrease much faster once
liver function is restored.
- Alkaline Phosphatase (ALP):
This enzyme is present in many tissues, so it is not very specific in
liver disease, but it appears very early in the progress of liver
disease, so your vet will look for it anyway. The levels of ALP are
often elevated in dogs who are on anti-convulsive medications. Levels
of ALP also tend to be high in young, growing dogs such as puppies.
- Gamma Glutamyltransferase (GGT): While this enzyme is found in the liver, its highest concentration is
found in the kidneys and pancreas. Large elevations of GGT are
pancreatitis and bile duct obstruction.
Liver Disease: Signs, Symptoms, and Diagnosis
Dr. Fleming, Sherwood Animal Clinic
Regina, Saskatchewan, Canada
Diagnosing Liver Disease in Dogs: What Do the Tests Really Mean?