Diagnosis of NAFLD & NASH in Children

How do doctors diagnose NAFLD in children?

Doctors use medical and family history, a physical exam, and tests to diagnose nonalcoholic fatty liver disease (NAFLD)—including nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH)—in children.

Medical and family history

The doctor will ask about the child’s history of health problems that increase the chance of developing NAFLD, such as

The doctor will ask about the presence of these health problems or NAFLD in the child’s family. Children with a family history of these health problems are more likely to develop NAFLD.

The doctor will also ask about diet and lifestyle factors that may make a child more likely to develop NAFLD and NASH, such as a lack of physical activity, eating a diet high in sugar and starch, or drinking sugary beverages.

Physical exam

During a physical exam, a doctor typically checks weight and height to calculate the child’s body mass index. The doctor will also look for physical signs of NAFLD or NASH, such as

  • an enlarged liver
  • signs of insulin resistance, such as darkened skin patches over the child’s neck or armpits
  • signs of cirrhosis, such as an enlarged spleen

What tests do doctors use to diagnose NAFLD in children?

Doctors use blood tests, imaging tests, and sometimes liver biopsy to diagnose NAFLD in children, to tell the difference between NAFL and NASH, and to check for other liver problems.

Blood tests

A health care professional may take a blood sample from the child and send the sample to a lab. The doctor may suspect NAFLD if the blood test shows increased levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The doctor may perform additional blood tests to find out if the child has other health conditions that may increase liver enzyme levels.

Imaging tests

If a blood test shows that a child has increased liver enzyme levels, the doctor may order imaging tests of the liver. While imaging tests cannot confirm a diagnosis of NAFLD or tell the difference between NAFL and NASH, imaging tests may show signs of other liver problems or may suggest that fat is present in the liver.

A commonly used imaging test is ultrasound. Ultrasound bounces safe, painless sound waves off organs to create an image of their structure. Ultrasound tests do not use radiation and are not painful.

Elastography is a newer type of test that may help determine whether a child has advanced liver fibrosis, or scarring. In some cases, doctors may order an elastography test to measure the stiffness of a child’s liver. Increased liver stiffness may be a sign of fibrosis.

Types of elastography tests include special ultrasound and magnetic resonance imaging (MRI) tests. MRI uses radio waves and magnets to produce detailed images of organs and soft tissues without using x-rays. Researchers are still studying the use of these tests to help diagnose NAFLD in children.

Liver biopsy

Liver biopsy is the only test that can prove a diagnosis of NAFLD, tell whether a child has NAFL or NASH, and show clearly how severe the disease is, including how much fibrosis—or scarring—is present. However, doctors may not recommend this test for all children with suspected NAFLD. In some cases, doctors recommend a liver biopsy to rule out other liver diseases. Doctors may also recommend a biopsy for children who have a greater chance of having NASH or scarring of the liver.

During a liver biopsy, a doctor will take a small piece of tissue from the liver. A pathologist will examine the tissue under a microscope to look for signs of damage and signs of the cause of liver disease.

Last Reviewed December 2021
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.