Fatty liver (steatosis) is an abnormal accumulation of certain fats (triglycerides) inside liver cells.
In the United States and other Western countries, the most common causes of fatty liver are consumption of large amounts of alcohol (see Alcohol), toxins, certain drugs, hereditary metabolic disorders, and metabolic abnormalities, such as excess body weight, insulin resistance (as can occur in diabetes), and high levels of triglycerides (a fat) in the blood. The combination of excess body weight, insulin resistance, and high triglyceride levels is called metabolic syndrome (see see Metabolic Syndrome). All of these conditions cause fat to accumulate in liver cells by causing the body to synthesize more fat or by processing (metabolizing) and excreting fat more slowly. As a result, fat accumulates and is then stored inside liver cells. Just consuming a high-fat diet does not result in fatty liver.
Rarely, fat accumulates in the liver during late pregnancy. This disorder, called fatty liver of pregnancy (see Fatty liver of pregnancy ) or microvesicular steatosis, is usually considered a different disorder from fatty liver.
The fatty liver may or may not be inflamed. Inflammation may develop into scarring (fibrosis). Fibrosis often progresses to cirrhosis (scarring that distorts the structure of the liver and impairs its function). Fatty liver (with or without fibrosis) due to any condition except consumption of large amounts of alcohol is called nonalcoholic fatty liver disease. This disorder develops most often in people with metabolic syndrome.
Fatty liver usually causes no symptoms. Some people feel tired or have vague abdominal discomfort. The liver tends to enlarge and can be detected by doctors during a physical examination.
If doctors suspect fatty liver, they ask about alcohol use. This information is crucial. Continued and excessive alcohol use can cause severe liver damage.
Blood tests to detect liver abnormalities, such as inflammation, are important (see Sidebar 1: Liver Function Tests) because inflammation may lead to cirrhosis. Additional blood tests help exclude other causes of liver abnormalities, such as viral hepatitis. Ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI) of the abdomen can detect excess fat in the liver but cannot always determine whether inflammation or fibrosis is present.
Liver biopsy may be necessary to confirm the diagnosis. For the biopsy, a doctor gives a local anesthetic to lessen any pain, then inserts a long hollow needle through the skin and into the liver to obtain a small piece of liver tissue for examination under a microscope (see Biopsy of the Liver). The biopsy can help determine whether fatty liver is present, whether it resulted from alcohol or certain other specific causes, and how severe the liver damage is.
Excess fat in the liver by itself is not necessarily a serious problem. For example, if alcohol is the cause, the fat can disappear, usually within 6 weeks, when people stop drinking. However, if the cause is not identified and corrected, fatty liver can have serious consequences. For example, if people continue to drink large amounts of alcohol or if a drug causing fatty liver is not stopped, repeated liver injury may eventually lead to cirrhosis.
Women with fatty liver of pregnancy have a worse prognosis (see Fatty liver of pregnancy).
Treatment focuses on controlling or eliminating the cause of fatty liver. For example, people should
Vitamin E and thiazolidinediones (such as rosiglitazone or pioglitazone, used to treat diabetes) may be of some help in treating fatty liver that is not caused by alcohol.
Last full review/revision August 2012 by Steven K. Herrine, MD