AST, ALT, GGTP And Alkaline Phosphatase In Dogs’ And Cats’ Livers

“ALT” stands for alanine transaminase, an enzyme present in the cells of mammalian livers. While the enzyme may also be found in a few other organs, the quantities are low enough to make ALT reasonably liver-specific. The same enzyme is also known by an older name, SGPT, which stands for serum glutamic pyruvic transaminase. Normal serum level of ALT in dogs should be between 12 and 118.

Some canine liver problems can be diagnosed by blood and urine tests.
Some canine liver problems can be diagnosed by blood and urine tests.

ALT is known as a “leakage enzyme,” meaning the cells that contain it must die in order for it to be released. Therefore, if serum ALT levels are up, some death of liver cells has occurred. However, it is important to recognize that there is not a direct correlation among the elevation of the enzyme, the amount of liver damage and the prognosis for the patient. However, trends may be followed that give an indication of improvement or worsening of liver disease.

Many diseases may affect ALT, as well as non-liver conditions. For example, congestive heart failure (CHF) may result in poor blood circulation, causing stagnation of liver blood flow and poor liver function. Some medications, most notably phenobarbital used for seizure control.

“AST” stands for aspartate transaminase, which is also an enzyme. The older name is “SGOT,” which stands for serum glutamic oxaloacetic transaminase. AST is also present in the liver and several other organs including skeletal muscle, heart muscle and red blood cells. Interpretation of the enzyme is similar to ALT, while recognizing that it is much less liver-specific. Normal level in dogs is 15-66.

Alkaline phosphatase is also present in the liver, as well as bone, placenta and other locations. From the liver, it normally moves into the intestinal tract along with bile through the bile ducts. However, if bile flow is obstructed, levels within the liver may rise sufficiently to ‘back up” into the bloodstream. Patients with rapidly growing bones, puppies and kittens, as well as pregnant animals, may have elevated alkaline phosphatase levels.

Bile ducts may become obstructed at the microscopic level, inside the liver, or the macroscopic level, in the large ducts that leave the gall bladder, pass through the pancreas and enter the intestinal tract, where bile aids in the digestion of fats.

GGTP or gamma glutamyl transpeptidase, also becomes elevated in biliary obstruction, and is much more specific than alkaline phosphatase. It is also a much newer test.

It is important to realize that these are not measurements of liver function, rather they are measurements of liver damage. Now, that won’t keep physicians or veterinarians from calling them liver function tests. It’s not that we don’t know better, it’s just the term used as an inappropriate shortcut. To assess the function of the liver, we will discuss bile acids in this series.

See you tomorrow, Dr. Randolph.

122 Comments

  1. Hi.
    My cat had been acting a little off since last 3-4 months. He is playing and eating just fine but had been having digestive issues. So we took him to the vet and they gave him some injections including CTS etc. but his conditions didn’t improve. So we regularly took him to vet dewormed him. And started giving him guttians st. He started improving but as soon as the medication ended he went back to having digestive issues. His diarrhoea started. We changed the vet he prescribed other medications no use. We had his CBT and liver pancreas and stool test done yesterday. Because the situation became serious and we saw blood in his stool. The result showed his Alt level to be 63 And ast to be 72. What should I do? Will he be alright? He doesn’t has anything serious right?

    • In our lab ALT is normal up to 118, AST to 66, so, I don’t see anything there to get excited about. Sounds like it’s time to ask your veterinarian for a referral to a board-certified internist who can ultrasound your kitty’s abdomen and submit some GI-specific lab test specimens. Please do this right away and report back so we’ll know what the findings are. Thanks for reading, Dr. Randolph.

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