What is nonalcoholic steatohepatitis (NASH)?

Causes and Symptoms

The liver
is a complex organ located in the right upper abdomen. It plays a role in converting carbohydrates, fats, and proteins from food into usable forms for the body. It also manufactures cholesterol, stores sugar, and metabolizes certain medications and chemicals. Nonalcoholic steatohepatitis (NASH) is characterized by the storage of excess fat in the liver, with associated inflammation. The cause of this disorder is not completely understood. The accumulation of excess fat in the liver is related to the body’s inability to use its own insulin, a common problem found in adults and children with central obesity. NASH is also found in individuals with other medical conditions, such as diabetes, metabolic syndrome, high blood pressure, and hyperlipidemia. Other causes of excess fat storage are certain medications, exposure to occupational toxins, and some surgical procedures. The excess fat causes damage to the cells of the liver that is similar to the damage caused by excess alcohol intake.

The majority of people with NASH have no symptoms, and the disorder is suspected from liver function tests. Studies have shown, however, that elevated liver enzymes do not always occur in individuals with NASH. If symptoms are present, then they may include fatigue or mild discomfort in the upper right side of the abdomen. The liver may be enlarged. Fatty liver may be identified on ultrasound, but a biopsy of the liver must be performed in order to determine the extent of the disorder. A liver biopsy
is a minor surgical procedure that is performed by inserting a needle into the liver through a small incision and removing cells for evaluation under the microscope. The disorder may range from inflammation of the liver to cirrhosis, a chronic, progressive disease with extensive scarring of the liver that causes destruction of liver cells. If the destruction advances, then the liver loses the ability to function. Severe liver disease occurs in approximately 20 percent of those with NASH.

Treatment and Therapy

Treatment goals include the identification and treatment of associated conditions and the reduction of insulin resistance. Adopting a healthy lifestyle is the primary treatment for NASH. Those who are overweight are encouraged to lose weight gradually and to exercise. Triglyceride and cholesterol levels should be kept within normal limits. Strict blood sugar control is indicated for diabetics with NASH. A few studies have found that daily vitamin E reduces abnormal liver enzymes. Insulin-sensitizing drugs, normally used by diabetics, have also shown promise for the treatment of NASH and its associated insulin resistance. Lipid-lowering drug studies have also shown some improvement in blood liver function tests, but not in the follow-up biopsy tests for inflammation and damage.

It is generally recommended that individuals with NASH avoid alcohol and certain medications, such as acetaminophen, that may further damage the liver. If the individual develops severe cirrhosis, then a liver transplant
may be necessary to avoid death.

Perspective and Prospects

In 1958, fatty liver disease was first identified in a small group of obese individuals. In 1980, the term nonalcoholic steatohepatitis was coined to describe a small group of patients at the Mayo Clinic who had liver biopsy findings similar to those with alcoholic liver disease. Since 2000, pediatricians have reported the presence of NASH in obese children, as well as in children with other endocrine disorders. The increase in obesity and diabetes in the United States has been linked to the increasing numbers of individuals diagnosed with NASH.

Diagnosis is confirmed with a liver biopsy, or, less commonly, with a noninvasive diagnostic method. Ultrasound and abdominal computed tomography (CT) scans are sometimes used, as are newer x-ray techniques and laboratory blood analyses.

Drug therapy continues to be investigated after promising pilot studies. Further study is also needed in the area of the disease process and its potential for progression in some individuals.

Bibliography:

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Harrison, Stephen A., and Adrian M. Di Bisceglie. “Advances in the Understanding and Treatment of Nonalcoholic Fatty Liver Disease.” Drugs 63, no. 22 (2003): 2379–2394.

Howson, Alexandra. "Nonalcoholic Fatty Liver Disease." Health Library, May 14, 2013.

“Liver Disease: Fat Inflames the Liver.” Harvard Health Letter 26 (February, 2001): 4.

Nakajima, Kenichirou, et al. “Pediatric Nonalcoholic Steatohepatitis Associated with Hypopituitarism.” Journal of Gastroenterology 40, no. 3 (March, 2005): 312–315.

"Nonalcoholic Fatty Liver Disease." Mayo Clinic, February 19, 2011.

Nonalcoholic Steatohepatitis." National Digestive Diseases Information Clearinghouse, April 30, 2012.

Porth, Carol M. “Disorders of Hepatobiliary and Exocrine Pancreas Function.” In Pathophysiology: Concepts of Altered Health States. 8th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins, 2010.