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 alcoholism, toxins, certain drugs, hereditary metabolic disorders, and metabolic abnormalities, such as excess body weight, insulin resistance, and high triglyceride levels in the blood. This combination of metabolic abnormalities is called the metabolic syndrome (see see Obesity and the Metabolic Syndrome: Metabolic Syndrome). These conditions cause fat to accumulate in liver cells either 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. Microvesicular steatosis, a rare form of fatty liver, can develop in certain genetically susceptible women during pregnancy.
The fatty liver may or may not be inflamed. Inflammation may then develop into scarring (fibrosis). Fibrosis often progresses into cirrhosis. Fatty liver (with or without fibrosis) due to any condition except alcoholism is called nonalcoholic steatohepatitis. This disorder develops most often in people with the metabolic syndrome.
Symptoms and Diagnosis
Fatty liver usually causes no symptoms. Some people may feel tired or have vague abdominal discomfort. The liver tends to enlarge and can be detected by the doctor during a physical examination. If doctors suspect fatty liver, they ask about alcohol use. This information is crucial. Continued and excessive alcohol use causes severe liver damage.
Blood tests to detect liver abnormalities, such as inflammation, are important (see Diagnosis of Liver, Gallbladder, and Biliary Disorders: Liver Function Tests) because this type of hepatitis 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 determine whether inflammation or fibrosis is present.
Liver biopsy may be necessary to confirm the diagnosis. For the biopsy, a doctor inserts a long hollow needle through the skin (after giving a local anesthetic to lessen any pain) and into the liver to obtain a small piece of liver tissue for examination under a microscope (see Diagnosis of Liver, Gallbladder, and Biliary Disorders: 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.
Prognosis and Treatment
Excess fat in the liver alone is not necessarily a serious problem. For example, if alcoholism is the cause, the fat can disappear, usually within 6 weeks, when people stop drinking. If the cause is not identified and remedied, fatty liver can have serious consequences. For example, if excessive alcohol use continues or a drug causing fatty liver is not stopped, repeated liver injury may eventually lead to cirrhosis. Microvesicular steatosis has a worse prognosis.
Treatment focuses on minimizing or eliminating the cause of fatty liver. People should stop taking a drug, lose weight, or take measures to control diabetes, lower triglyceride levels, or stop drinking.
Last full review/revision September 2007 by Eldon A. Shaffer, MD