by Robert Fusco, MD
Your liver, located under your right rib cage, normally weighs about three pounds and is the body's second largest organ. (Your skin is the largest.) It is a complex chemical factory which produces many important substances such as bile, digestive enzymes, clotting factors, cholesterol, and proteins. It is essential in the metabolism of fats, carbohydrates, proteins, the various vitamins and minerals. It helps control the level of blood sugar and fats. It cleanses the blood and detoxifies drugs and potentially harmful chemicals such as alcohol.
The liver is a storehouse for blood, vitamins and minerals, and glycogen - the stored form of sugar - the body's major fuel. Overall, each liver cell has over 200 chemical functions to perform. It's an amazingly complicated machine and largely unappreciated - until something goes wrong.
What is a fatty liver?
Almost all of the organs in the body contain some fat. That is not necessarily a bad thing. Fat cells provide insulation, protection, and are an efficient way to store extra energy. After a typical meal, dietary fat is absorbed by the intestines and enters the blood stream which carries the fat directly to the liver. Normally, this fat is metabolized in the liver and converted to energy. If the amount of fat delivered is excessive, it is stored in the liver and other tissues. The normal liver contains about 5% fat. The rest of the liver is made up of liver cells called hepatocytes which do all the work of the liver. When the amount of fat in the liver exceeds 10%, healthy liver cells are replaced by fat cells. This condition is termed a "fatty liver," or steatosis.
How common is a fatty liver?
Recent surveys have shown fatty liver to be much more common than previously recognized. In fact, it has become the most common cause of abnormal liver enzymes (blood tests) in the US population. It now affects about 25% of all adult Americans.
Who gets it?
The typical patient is overweight and diabetic, although fatty liver may occur in individuals of normal weight. Patients often have elevated levels of cholesterol and triglyceride in the blood, but eating fatty foods is not a direct cause of fatty liver.
It is more common in women, but affects both sexes. It is also quite common in those who consume excessive amounts of alcohol. There is no evidence that heredity plays a significant role in this disease. It is not passed from parent to child.
What causes a fatty liver?
As mentioned above, the main cause is deposition of excessive fat within the liver. There are two basic categories of fatty liver - that seen in alcoholics and that which occurs in non-drinkers.
Alcoholic fatty liver
It has been recognized for centuries that chronic alcoholism can cause progressive liver failure. The first stage of alcoholic liver disease is a fatty liver (alcoholic steatosis). At this stage, the damage is often reversible if the individual becomes totally abstinent; however, with continued drinking, the outcome is dismal. Liver cells die and are replaced by scar tissue. When excessive scar tissue develops (cirrhosis), the liver fails. So, a fatty liver in an alcoholic who keeps drinking is quite serious.
Non-alcoholic fatty liver disease (NAFLD)
Most NAFLD is caused by obesity and type II diabetes both of which, unfortunately, affects more and more Americans each year - now even children. According to the Centers for Disease Control and Prevention (CDC), twelve U.S. states now have an adult obesity rate of 30 percent more. There were none in 2000.
Obesity is defined as a Body Mass Index or BMI of 30.0 or higher. (You can calculate your BMI here.)
Until recently, it was believed that in non-alcoholics a fatty liver was just a curiosity - a consequence of being overweight or a diabetic. New scientific studies have identified non-alcoholic fatty liver disease (NAFLD) as a separate disease, also with potentially serious consequences. In fact, NAFLD now accounts for 75% of patients with chronic liver disease. While rates of liver disease due to hepatitis B, hepatitis C, and alcohol have remained steady, NAFLD continues to rise. The increasing prevalence of obesity and NAFLD among U.S. children and adolescents makes future predictions more dire.
NAFLD includes several different levels of severity:
1. Simple Fatty Liver (steatosis)
Simple fatty liver is the deposition of fat in the liver. This condition usually does not cause liver inflammation or scar tissue, and the risk of progressive liver damage is low. There are no symptoms.
2. NASH (Non-alcoholic steatohepatitis)
In 1980, scientists at the Mayo Clinic noted changes on liver biopsies in non-alcoholics that looked very much like the liver damage seen in chronic alcoholics who continue to drink. In addition to excess fat, there were signs of dying liver cells (necrosis), and inflammation. They termed this condition non-alcoholic steatohepatitis, commonly referred to as NASH. (The phrase "steato" simply means fat and "hepatitis" means liver inflammation.) The presence of dying liver cells and inflammation makes NASH a more severe form of fatty liver. Patients with NASH are one step closer to developing liver cirrhosis. NASH is now the third most common cause of liver disease in adults in the United States (after hepatitis C and alcohol). It is the most common cause of liver disease in adolescents. It is more common in women than men and often has no symptoms until it's too late.
Fatty liver has become the most common cause of cirrhosis in non-drinkers. It is now believed that up to 25% of non-drinkers who have NASH will also go on to develop liver cirrhosis. Why this happens is not known.
What are the symptoms of a fatty liver?
Fatty liver usually produces no symptoms. Fat accumulation is a gradual process that occurs silently over many years. Eventually, the liver becomes enlarged and may cause a vague discomfort in the right upper abdomen.
How is it diagnosed?
The typical scenario is a patient who has routine blood tests performed for another reason and is told that the "liver enzyme" reading is unexpectedly elevated. Perhaps they tried to donate blood and were rejected. It may have been an insurance physical or just a routine checkup. The most common abnormality in the blood tests is two- to three-fold elevation in liver enzymes called SGOT (also termed AST) and SGPT (also termed ALT). In non-alcoholic fatty liver, other liver blood tests are usually normal. In any case, these individuals are usually referred to a specialist to investigate the underlying cause.
If there is a history of chronic alcohol abuse, the underlying cause of abnormal liver enzyme blood tests is usually obvious. In non-drinkers, investigation usually focuses on searching for other potential causes such as viral hepatitis, hemochromatosis (iron overload), gallstones, cancer, or fatty liver. Non-alcoholic fatty liver is suspected in any adult who has unexplained elevated liver blood tests and drinks no more than two alcoholic drinks daily. To investigate further, more blood tests are usually required to rule out other causes of liver disease.
Imaging studies such as a sonogram, MRI, or CT scan are helpful in ruling out cancer and gallstones. They can also help determine if the liver contains excessive fat, but cannot distinguish between benign steatosis and the more serious steatohepatitis (NASH). If NASH is suspected or the diagnosis unclear, a needle liver biopsy is often performed. This test allows the doctor to obtain a small piece of liver tissue to examine directly under the microscope. Magnified a thousand times, the two photos below show how a fatty liver replaces normal functioning liver cells with clear globules of fat:
How is a fatty liver treated?
There is much hope for the future as medical scientists are searching for a cure. There are many areas of investigation. However, there is currently no proven medical or surgical treatment to directly reverse a fatty liver. Therefore, therapy is usually directed at the underlying cause. Alcohol must be stopped completely. Potentially offending medications may need to be changed, if possible. Uncontrolled diabetes must be better controlled. High blood fats need to be reduced. Ultimately, however, the only proven treatment for fatty liver is weight loss. Excessive weight must be lost through a diet and exercise program. Weight loss should be gradual and not exceed 5 pounds a week since rapid weight loss has been associated with progression of this disease.
How can one avoid a fatty liver?
Do not drink excess alcohol. If you drink, do not exceed two drinks per day on a regular basis. Maintain a proper body weight. Eat a healthy diet - overeating and extreme dieting can result in a fatty liver. See your doctor for periodic examination and blood tests. Diabetes and high blood fats should be aggressively treated.
Fatty liver is a common silent process that can occur both in drinkers and in non-drinkers. It should be suspected if liver blood tests are unexpectedly elevated, especially in those who are alcoholics, obese, diabetic, or have high blood fats. Simple non-alcoholic fatty livers (steatosis) have a benign prognosis, but NASH (steatohepatitis) can be progressive and lead to cirrhosis with liver failure. As yet, there is no specific treatment, so therapy is directed to the underlying cause.
For more information, contact the website: LiverFoundation.org