Simple fatty liver is not a disease, since it does not damage the liver, but is a condition that can be identified by taking a sample of liver tissue (liver biopsy) and examining it under a microscope. Another term often used to describe this condition is fatty infiltration of the liver. Fat accumulates in the liver usually in connection with heavy use of alcohol, extreme weight gain or diabetes mellitus. Fatty liver can also occur with poor diet and certain illnesses, such as tuberculosis, intestinal bypass surgery for obesity, and certain drugs such as corticosteroids. Fatty liver is usually suspected in a patient with the diseases or conditions described above. The patient may have an enlarged liver or minor elevation of liver enzyme tests. Several studies show that fatty liver is one of the most common causes of isolated minor elevation of liver enzymes found in routine blood screening.
To find out for certain whether a patient has fatty liver requires that a sample of liver tissue be obtained (biopsy). Images of the liver obtained by an ultrasound test or by a computed tomography (CT) scan can suggest the presence of a fatty liver. In the ultrasound test, a fatty liver will produce a bright image in a ripple pattern. A CT scan will show a liver that is less dense than normal. It is not certain how fatty liver occurs. A patient has fatty liver when the fat increases the weight of the liver by 5 percent. Possible explanations for fatty liver include the transfer of fat from other parts of the body, or an increase in the extraction of fat presented to the liver from the intestine. Other explanations are that the liver reduces the rate it breaks down and removes fat. Eating fatty food by itself does not produce a fatty liver. Simple fatty liver is not associated with any other liver abnormalities such as scarring or inflammation. It is a common finding in patients who are very overweight or have diabetes mellitus.
Patients who drink too much alcohol for many years may develop alcoholic liver damage that includes fatty liver. Alcoholism could also result in inflammation of the liver (alcoholic hepatitis) and/or scarring (alcoholic cirrhosis). Evidence suggests that while fatty liver is usually present in patients with excessive intake of alcohol, fatty liver does not by itself lead up to the development of alcoholic hepatitis or alcoholic cirrhosis.
An inflammation of the liver associated with an increase of fat deposits may occur in middle-aged, overweight, and often diabetic patients who do not drink alcohol. This disease, which resembles alcoholic hepatitis, is called nonalcoholic steatohepatitis (NASH). This fatty tissue in the liver may break up (steatonecrosis) and the patient may develop cirrhosis (scarring of the liver). Some studies have shown that 20 percent to 40 percent of people who are grossly overweight will develop NASH. However, just because a patient is grossly overweight does not mean he will develop NASH. Some researchers have connected the development of NASH with poor control of diabetes mellitus, rapid weight loss, or in women, the taking of hormones (estrogen). The treatment of fatty liver is related to the cause. It is important to remember that simple fatty liver does not require treatment, since it does not result in damage to liver cells or clinical disease. Obese patients with fatty liver will have reduction or loss of excess fat in liver cells, as well as in other cells in the body, if substantial weight loss can be achieved. Patients who drink alcohol to excess will also have a loss of fat in the liver when alcohol is discontinued. Good control of diabetes mellitus with diet, drugs, or insulin also decreases the fat content in the liver.
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