Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease closely linked to obesity and diabetes, characterized by too much fat in the patient’s liver.
In a patient with NAFLD, fat is deposited within his or her liver cells (called steatosis), which can lead to injury to the organ. Steatosis can also be caused by excessive alcohol consumption; however, NAFLD is specific to patients with liver fat who consume little or no alcohol.
- Nonalcoholic fatty liver (simple steatosis) is the mildest form of NAFLD. The patient’s liver does contain an excessive amount of fat (up to 5 percent), but it has not led to any damage. Your physician may suspect fatty liver if your liver enzymes are elevated, and treatment usually involves a program of weight loss through diet and exercise. About 25 percent of patients with simple steatosis proceed to the next stage of the disease.
- Nonalcoholic steatohepatitis (NASH) is a more serious form of NAFLD, in which the excess fat results in inflammation, liver cell damage, and some scarring. NASH can currently be diagnosed only via liver biopsy, and about 20 percent of NASH patients may develop the third and most severe form of NAFLD within 20 to 30 years.
- NASH-related cirrhosis (NRC), the most severe form of NAFLD, is characterized by scarring throughout the liver that affects the organ’s function and structure. Cirrhosis may lead to liver failure, and in some patients, a liver transplant may be needed.
Current statistics show that about 20 percent of the adult U.S. population has simple steatosis and 2 to 3 percent have NASH. NASH-related cirrhosis is now the third most common reason for requiring a liver transplant, and patients with NRC have an increased risk of developing liver cancer.
Risk Factors for NAFLD
Individuals who are obese or diabetic, or who have high lipids or high blood pressure, are at risk for developing NAFLD. These factors are often linked to insulin resistance, a reduced sensitivity to the effects of insulin, and may lead to excessive amounts of fat being deposited in the cells of the liver.
The inflammatory response in NASH can be caused by:
- oxidative stress—increased oxidant production that can cause cells to degenerate—inside the liver cells, and
- the fat cells releasing toxic inflammatory mediators—molecules such as cytokines that are released by cells as part of the immune response.
Symptoms of NAFLD
Nonalcoholic fatty liver disease is usually “silent,” in that it presents few or no detectable symptoms in early stages. The patient may experience an ache in the upper right side of the abdomen, and a close physical examination may reveal an enlargement of the liver and skin discoloration around the neck and armpits (acanthosis nigricans).
As the disease progresses, symptoms of liver cirrhosis may develop, including weakness, fatigue, and jaundice (yellowing of the eyes or skin). (Learn more about liver cirrhosis)
Because it presents few if any symptoms, NAFLD may be difficult to diagnose. Your physician may suspect it if a routine blood test shows elevated levels of certain liver enzymes, particularly AST (aspartate aminotransferase) and ALT (alanine aminotransferase). Liver cells release these enzymes into the bloodstream if the organ is damaged.
While AST and ALT levels are helpful in indicating the presence of NAFLD, determining the extent of the disease (see Types of NAFLD) requires further testing. At this point, patients are usually referred to a hepatologist (liver specialist), who may perform a liver biopsy to determine the type of NAFLD and the extent of any scarring.
If you’re diagnosed with simple steatosis (the mildest form of NAFLD), your doctor will probably recommend weight loss through lifestyle changes such as diet and exercise. He or she will probably also recommend limiting or eliminating your alcohol consumption.
If testing indicates the presence of nonalcoholic steatohepatitis (NASH), weight loss will also be recommended as well as steps to control diabetes, high blood pressure, and high lipid levels. Even a modest weight loss of 5 to 10 percent of your body weight can decrease the amount of fat in the liver by up to 40 percent.
For information on treatment for NASH-related cirrhosis (NRC), see Liver Cirrhosis.
To find out more about the Methodist Center for Liver Disease and Transplantation, call us at 713-441-8839 or 866-94-LIVER (866-945-4837) or send us an email.