Dogs suffering from liver diseases may exhibit clinical signs, but a liver test is mandatory for determining the nature of the disease. However, dog owners do not always know what these tests imply or what the results mean. Below are listed some of the most common tests performed as part of the diagnosis of liver diseases, along with a brief explanation about the results.
Bile Acid Response Test
This test is able to reveal liver dysfunctions that become more noticeable after eating. More precisely, this test indicates whether the bile acid levels are considerably elevated after eating. In case the results are not conclusive enough, the bile acid response test needs to be followed by such tests as a clotting panel and an ultrasound biopsy. Sometimes only a small elevation of the bile acid levels is noticed, and in such situations, the best thing to do is to repeat the lab testing.
Bile Acid Test
Bile acid is produced in the liver as cholesterol gets synthesized. After dietary fat is processed by micelles, which are aggregates of molecules formed with the help of bile acid, the latter needs to be recycled, and this process also takes place in the liver. If high levels of bile acid are detected in the blood, it means that the liver has a problem that prevents it from recycling bile acid properly.
Cholesterol Levels
High serum cholesterol levels do not always indicate a liver disease, as they are also common to pancreatitis, diabetes and hypothyroidism. On the other hand, very low serum cholesterol levels may indicate hepatic failure, a fact that makes this test an important part of canine liver disease diagnosis.
Liver Biopsy
Before doing this test, the veterinarian needs to make sure your dog does not have any blood clotting problems, as the liver synthesizes some of the compounds used in this process. If blood clotting is not normal, there is a great risk of severe hemorrhage and even death. In such cases, the alternative is represented by ultrasound liver biopsies.
Liver Enzymology
The purpose of this test is to determine the cellular concentrations of ALT (alanine aminotransferase) and ALP (alkaline phosphatase), two enzymes that are specific to the liver. Levels that are two to three times higher than usual will not raise a question, while levels from four to five times higher than the usual typically indicate a non-hepatic condition such as:
- Cardiac failure
- Hemolytic anemia
- Inflammatory gastrointestinal disease
The highest concentrations of ALT are noticed in the cytosol (intracellular fluid) after the necrosis of liver cells.
High ALP concentrations, on the other hand, are common when the bile cannot flow from the liver into the duodenum. This condition, which is known as cholestasis, may be caused by factors that are found inside or outside the liver. Cholestasis determines an elevated production of ALP, which is then released into the serum.
Serum Protein Levels
The amounts of serum albumin and serum globulins need to be determined in order to evaluate the liver function. If this function drops by more than 70 percent, hypoalbuminaemia will be noticed. This condition appears in animals that suffer from cirrhosis or severe diffuse necrosis.
High levels of serum globulin indicate that the hepatic reticuloendothelial system does not work properly. On the other hand, low levels also indicate a problem, as a great part of these proteins is produced by the liver.
Ultrasound Liver Biopsy
This type of test is preferred when a normal biopsy cannot be performed because of blood clotting problems. The results indicate differences between hepatic and post-hepatic cholestasis, as well as differences between cellular infiltration and homogenous enlargement.