The liver is an important organ that plays a role in multiple physiological processes. There are many conditions that can cause elevated liver enzymes, ranging from a simple infection to cancer. A physician will evaluate a patient's symptoms and then run liver enzyme tests on a blood sample, usually in conjunction with other blood work. A diagnosis generally is not made based solely on liver enzyme levels.
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The liver is the largest organ in the human body. It aids in digestion, metabolism, protein synthesis and general detoxification. It also produces bile, used in digestion to emulsify fats. Some of this bile is stored in the gallbladder, and abnormal liver enzyme levels can thus indicate a problem with the gallbladder. The liver also plays a role in the immune system, as phagocytes are dispersed throughout the liver tissue.
Significance
Since the liver is a critically important organ and its proper functioning is imperative to many physiological processes, elevated liver enzymes can be due to a multitude of conditions in several different organs. Infection or inflammation of the liver, gall bladder, or bile ducts can all lead to elevated liver enzymes, as can more serious conditions like cancer, cirrhosis and congestive heart failure.
Types
These are the liver enzymes that may be elevated, along with what conditions might produce these abnormal laboratory results.
ALT (alanine transaminase): When liver cells become damaged by injury or illness, this chemical leaks into the bloodstream. If there has been no injury, high levels of ALT may be caused by an infection, like viral hepatitis, or an overdose of drugs processed in the liver, like acetaminophen.
AST (aspartate transaminase): This enzyme is also raised in cases of liver damage. However, it is not specific to the liver, and may be elevated if there is damage to the kidneys, brain, heart or skeletal muscle. If AST is high but ALT is normal, the damage is probably not in the liver. If ALT and AST are both high, then the liver is likely to be affected.
ALP (alkaline phosphatase): High ALP is normal in children and pregnant women. In other patients, it may indicate an inflamed or blocked bile duct, inflammation of the gall bladder, cirrhosis, hepatitis, or liver tumors. Some prescription drugs may also cause high ALP levels.
GGT (gamma glutamyl transpeptidase): Elevated levels may indicate hepatitis, cirrhosis, bile duct obstruction or liver tumors. It may also be raised by congestive heart failure, alcohol usage and some prescription drugs.
TBIL (total bilirubin) and DBIL (direct bilirubin): High bilirubin levels can cause jaundice. When total bilirubin is elevated, direct bilirubin levels can help determine the problem. If DBIL is normal, the problem may be cirrhosis or hepatitis, whereas if both TBIL and DBIL are elevated, then there is likely an excretion problem in the gallbladder or a bile duct.
ALT (alanine transaminase): When liver cells become damaged by injury or illness, this chemical leaks into the bloodstream. If there has been no injury, high levels of ALT may be caused by an infection, like viral hepatitis, or an overdose of drugs processed in the liver, like acetaminophen.
AST (aspartate transaminase): This enzyme is also raised in cases of liver damage. However, it is not specific to the liver, and may be elevated if there is damage to the kidneys, brain, heart or skeletal muscle. If AST is high but ALT is normal, the damage is probably not in the liver. If ALT and AST are both high, then the liver is likely to be affected.
ALP (alkaline phosphatase): High ALP is normal in children and pregnant women. In other patients, it may indicate an inflamed or blocked bile duct, inflammation of the gall bladder, cirrhosis, hepatitis, or liver tumors. Some prescription drugs may also cause high ALP levels.
GGT (gamma glutamyl transpeptidase): Elevated levels may indicate hepatitis, cirrhosis, bile duct obstruction or liver tumors. It may also be raised by congestive heart failure, alcohol usage and some prescription drugs.
TBIL (total bilirubin) and DBIL (direct bilirubin): High bilirubin levels can cause jaundice. When total bilirubin is elevated, direct bilirubin levels can help determine the problem. If DBIL is normal, the problem may be cirrhosis or hepatitis, whereas if both TBIL and DBIL are elevated, then there is likely an excretion problem in the gallbladder or a bile duct.
Identification
Normally, a physician will order other tests along with those for liver enzymes. These can include a complete blood count, (CBC), which will test levels of white and red blood cells or specific tests for viruses such as hepatitis. Liver enzymes ALT, AST, ALP and bilirubin are also included on the Comprehensive Metabolic Panel, which tests kidney function, protein levels, electrolytes, glucose and calcium. A diagnosis is then made based on the outcome of all the blood tests and the patient's symptoms. If cancer is suspected, a biopsy may be performed. CAT scans and ultrasounds may also be used to confirm a diagnosis.
Prevention/Solution
Curative treatments will of course depend upon the underlying cause of the elevated liver enzymes. Solutions may include changes in diet and medication, antibiotics and anti-inflammatory drugs. Surgery may be necessary if there are gallstones, a blocked bile duct or a tumor. Chemotherapy and/or radiation may be necessary in cancer is discovered. In cases of cirrhosis and other chronic conditions, sometimes a liver transplant is required.
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