The liver is a complex organ that carries out many important functions in babies. Located in the right upper part of the abdomen, the liver helps detoxify the body from noxious drugs and substances. It also stores vitamins and minerals, produces proteins and enzymes, and manufactures clotting compounds. When the liver is damaged, its enzymes escape into the bloodstream where they can be detected by a series of blood tests. An elevation of the liver enzymes in babies can indicate serious health problems.
The liver enzymes are detected in a battery of tests called the liver or hepatic panel. The main enzymes used to check for liver damage are AST, or aspartate transaminase, and ALT, and alanine transaminase. According to Lab Tests Online, ALT is useful in the detection and diagnosis of liver disease because it is released into the bloodstream before more obvious signs of liver disease appear. AST is not as specific to a baby's liver disease, as this enzyme is also present in a baby's saliva and muscle cells.
According to the Nemours Foundation, the term hepatitis denotes an inflammation of the liver, regardless of the cause. The elevation of the liver enzymes reflects hepatitis. The most common causes of elevated liver enzymes in babies include the hepatitis viruses, including hepatitis A, B, and C; infection with the Epstein-Barr virus, which cause mononucleosis; and cytomegalovirus, a microbe that can cause premature birth, seizures, jaundice, and elevation of the liver enzymes. Other causes of elevated liver enzymes in babies include biliary atresia, in which the bile ducts, the tubes that drain bile into the intestine, become blocked, leading to liver damage; and autoimmune liver disease, in which the body's own immune system attacks the liver tissue.
The symptoms of liver disease, which correspond to an elevation of the liver enzymes, include jaundice, or a yellowish tinge of the skin; liver enlargement, which in babies can cause abdominal distension and pain; and nausea, vomiting, and weight loss. According to the University of Chicago Children's Hospital website, biliary atresia causes dark urine, pale stools, jaundice, easy bleeding and itching.
Babies with progressive liver disease and chronic elevation of the liver enzymes can suffer from portal hypertension, an abnormally high blood pressure of the vein that supplies the liver, which can cause abdominal distension and bleeding of the vein in the esophagus; and liver encephalopathy, a worsening of brain function that leads to confusion, drowsiness, loss of consciousness and coma.