How Doctors Diagnose NASH

Medically Reviewed By William C. Lloyd III, MD, FACS
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Nonalcoholic steatohepatitis (NASH) is a liver condition that damages liver tissue and causes the organ to malfunction. NASH usually occurs as a progression from nonalcoholic fatty liver disease (NAFLD). The hallmark signs leading to a NASH diagnosis include inflammation of the liver along with excessive amounts of fat in the liver tissue and damaged liver cells. The diagnosis of NASH can take some time, as your healthcare provider will want to rule out other potential causes of any liver inflammation or scarring (cirrhosis), such as viral hepatitis. The diagnostic process for NASH usually includes several steps.

Preliminary Diagnostic Tests for NASH

Your doctor may pick up signs of NASH from a physical exam and blood work, but an imaging study is necessary to see the liver disease directly.

Physical Exam

No single test exists to diagnose NASH, so healthcare providers work through a series of tests to arrive at a diagnosis. They will begin by conducting a thorough physical exam that includes palpating (feeling) the area over your liver. A skilled provider can feel an enlarged liver by palpating just below the right rib cage.

Your care professional also will evaluate your weight and body mass index, as people with a high BMI face a greater risk of developing NAFLD and NASH. Your provider also will look for physical signs of liver dysfunction, such as yellowing of the skin or the whites of the eyes (jaundice).

Blood Test

As part of the diagnostic process, your doctor will order liver function tests. A NASH blood test result will have higher than normal liver enzyme levels. If certain enzyme levels are high, your healthcare provider may order additional blood tests to determine whether or not some other medical condition is causing your liver dysfunction. (Healthcare providers may order a comprehensive metabolic panel at annual physicals, which can reveal liver and other organ problems.)

Imaging Studies

Your healthcare provider may order an ultrasound exam, CT study, or MRI to create images of your liver. These images can show if your liver is enlarged. Imaging studies also can show whether your liver contains nodules (bumps) or a tumor. This allows your healthcare provider to rule out conditions like cancer as the cause of your liver dysfunction.

NASH causes liver fibrosis (stiffening) and cirrhosis (scarring), which cannot be detected by common imaging tests. A diagnosis of NASH cirrhosis may involve specialized imaging tests like transient elastography, which uses a special type of ultrasound device, or magnetic resonance elastography (MRE), which uses a combination of MRI and ultrasound technologies.

Advanced Testing for NASH

The NASH diagnosis criteria include:

  • Excessive amounts of fat in the liver
  • Liver cells damaged by fibrosis or cirrhosis

If all three of these criteria do not exist, then the diagnosis likely will be NAFLD instead of NASH.

To evaluate your liver tissue for inflammation and damage, your healthcare provider likely will perform a liver needle biopsy. This painless test removes a few liver cells for examination under a microscope. The pathologist reviewing the tissue sample will document whether the sample meets the NASH criteria.

NAFLD and NASH usually do not produce any symptoms and often are detected during routine blood tests or imaging studies performed for another reason (such as prior to abdominal surgery). Reversing the liver damage caused by NASH can be challenging, and no medication exists to treat fatty liver disease or NASH.

To protect your liver and avoid conditions like NAFLD and NASH, maintain a healthy body weight, exercise regularly, and eat a heart-healthy diet that includes plenty of fresh vegetables and fruits, lean proteins, whole grains, and healthy fats.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Mar 26
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  2. Diagnosis of NAFLD and NASH. U.S. National Institute of Diabetes and Digestive and Kidney Diseases.
  3. NASH Diagnosis. American Liver Foundation.
  4. NASH Treatment. American Liver Foundation.