Fatty Liver

Fatty liver is an excessive accumulation of a type of fat (triglyceride) inside the liver cells. In western countries, the most common causes of fatty liver are alcoholism, obesity, diabetes, and elevated serum triglyceride levels. Other causes include malnutrition, hereditary disorders of metabolism (such as the glycogen storage diseases, and drugs (such as corticosteroids, tetracycline, and aspirin). The mechanism by which these diseases or factors cause fat to accumulate within liver cells is not known. Simply eating a high-fat diet, for example, does not produce a fatty liver. One possible explanation is that these diseases or factors slow the rate at which fat is processed (metabolized) and excreted by the body. The resulting buildup of fat within the body, according to this theory, is then stored inside the liver cells.
Sometimes the cause of fatty liver is not clear, especially when it occurs in newborns; however, it is likely to be a defect in the mitochondria of the liver cells.
In some people, a fatty liver not due to alcohol abuse or drugs and toxins but associated with obesity, diabetes mellitus, and raised serum triglycerides will progress to scarring (fibrosis) and cirrhosis, possibly because of underlying inflammation. This type of fatty liver is sometimes referred to as nonalcoholic steatohepatitis.

Symptoms and Diagnosis
Fatty liver usually produces no symptoms. In rare cases, however, it results in jaundice (a yellowish discoloration of the skin and the whites of the eyes), nausea, vomiting, pain, and abdominal tenderness.
A physical examination that reveals an enlarged liver without any other symptoms suggests fatty liver. Liver function tests are also performed to determine if there is a liver abnormality, such as inflammation, which sometimes accompanies the extra fat in the liver cells and can be associated with the development of cirrhosis in nonalcoholic steatohepatitis. Excess fat in the liver can be detected on abdominal ultrasound. The diagnosis may be confirmed by a liver biopsy, in which a doctor inserts a long hollow needle through the skin to obtain a small piece of liver tissue for examination under a microscope.

Prognosis and Treatment
Although excessive fat in the liver may not in itself be a serious problem (the fat can disappear, for example, if the person stops drinking), its underlying cause might be. For example, repeated liver injury from toxic substances such as alcohol may eventually progress from fatty liver to cirrhosis (severe scarring of the liver). Therefore, treatment of fatty liver aims at minimizing or eliminating the underlying cause of the disorder.

Known Causes of Fatty Liver

• Obesity
• Diabetes
• Chemicals and drugs (such as alcohol, corticosteroids, tetracyclines, valproate, methotrexate, carbon tetrachloride, and yellow phosphorus)
• Malnutrition and a low-protein diet
• Pregnancy
• Vitamin A toxicity
• Bypass surgery of the small intestine
• Cystic fibrosis (most likely accompanied by malnutrition)
• Hereditary defects in glycogen, galactose, tyrosine, or homocystine metabolism
• Medium-chain aryl dehydrogenase deficiency
• Cholesterol esterase deficiency
• Phytanic acid storage disease (Refsum's disease)
• Abetalipoproteinemia
• Reye's syndrome

(Merck)