What does the liver do?
The famous French physiologist Claude Bernard in 1847 called the liver "The chief chemical factory of the body."
The liver is in the upper right part of the abdomen, under the rib cage. It has many functions which include:
- Storing glycogen, a chemical made from sugars. When required, glycogen is broken down into glucose which is released into the bloodstream.
- Helping to process fats and proteins from digested food.
- Making proteins that are essential for blood to clot (clotting factors).
- Processing many medicines which you may take.
- Helping to remove or process alcohol, poisons and toxins from the body.
- Making bile which passes from the liver to the gut and helps to digest fats.
What is Nonalcoholic Fatty Liver Disease (NAFLD)?
NAFLD is a group of conditions where
extra fat collects in the liver of people who drink little or no alcohol (less than 2 drinks a day).*
The most common form of NAFLD is a benign condition called
simple steatosis (steatosis means fat). In simple steatosis, fat accumulates in the liver cells, but probably does not damage the liver.
One out of three people with NAFLD have a more serious condition called
non-alcoholic steatohepatitis (NASH). Fat accumulation in NASH is linked with inflammation and scarring. NASH can be a serious condition that may lead to severe liver scarring and cirrhosis.
Cirrhosis is when liver tissue is replaced by scar tissue which results in the inability of the liver to work properly and a risk of liver cancer. Some patients who develop cirrhosis may eventually require a liver transplant (surgery to remove the damaged liver and replace it with a "new" liver).
What causes NAFLD /NASH?
The most common causes of NAFLD are obesity and diabetes. NAFLD is considered part of the metabolic syndrome characterized by high blood sugars, being overweight or obese, high cholesterol and triglycerides, and high blood pressure. Having any of these characteristic puts you at risk of having NAFLD. NAFLD can also be caused by certain medications, gastric bypass surgery , malnutrition , rapid weight loss, some chemicals and metabolic diseases.
Less is known about what causes NASH to develop. There is ongoing research focusing on how NASH develops.
How common is NAFLD/NASH?
Due to the increase in obesity, NAFLD is now the most common chronic liver disease in adults in the United States, Australia, Asia and Europe. It is estimated that about one out of every four adults and one out of every 20 children in the United States have NAFLD. Obesity is thought to be the most common cause of NAFLD. It is estimated that two-thirds of obese adults and half of obese children have NAFLD.
About 2 to 5 percent of adult Americans and up to 20 percent of those who are obese may suffer from the more severe condition NASH. The number of children who have NASH is not known. Over the last ten years, the rate of obesity in our country has doubled in adults and tripled in children and teenagers, which explains why NAFLD and NASH are becoming more common.
What are signs and symptoms of NAFLD/NASH?
Nonalcoholic fatty liver disease usually causes no signs and symptoms. When it does, they may include weakness, pain in the upper right abdomen and weight loss. Physical examination is usually normal, but some might have slightly enlarged liver on physical examination. Some children may have patchy, dark discoloration of the skin present (acanthosis nigricans) most commonly over the neck and the under arm area.
How is NAFLD/NASH diagnosed?
To make a diagnosis of NAFLD, your doctor will take a detailed history, perform a full physical examination and routine blood tests. If any of these are abnormal he may go on to ask for a liver ultrasound scan and even a liver biopsy. A liver biopsy involves inserting a small needle through the skin after local anesthesia is given to obtain a small piece of the liver for microscopic evaluation. Liver tissue from people with NASH will show inflammation and scarring in addition to fat in the liver. In simple steatosis, only fat is present. The liver biopsy provides important information about the amount of scarring within the liver, which would not be obvious on a blood test, ultrasound, or an x-ray alone. Liver biopsy rarely carries serious risks including bleeding and you should discuss the risks and benefits with your physician.
What are the risks of having NAFLD/NASH?
Most people with NAFLD, especially those with simple fatty liver with no inflammation, have little or no problems from the condition. In contrast, about a quarter of people with NASH may have scarring of the liver that gets worse with time. In general, this is a slow process and can take years and even decades to occur.
How is NAFLD/NASH treated?
At this moment there is no medical treatment or drug that can undo fatty liver disease. As mentioned, a few studies have suggested that weight loss can help reduce the fat within the liver. Weight loss by both lifestyle changes and pharmacologic measures (orlistat) of at least 5-10% has been significantly associated with improvement in NASH. Therefore, it is important for people with fatty liver to lose weight if they are overweight or obese, increase their physical activity, follow a balanced diet and avoid alcohol and unnecessary medications. It is also important to control blood sugars and treat high cholesterol levels. While the role of weight loss after bariatric surgery in the treatment of NAFLD and NASH is still unclear, surgical weight loss procedures can be considered where appropriate. We are currently conducting a
trial on bariatric surgery in patients with NASH.
Cytoprotective agents such as UDCA (ursodeoxycholic acid ) alone have been shown to have no benefit in patients with NAFLD. Some promising results have been seen with medication such as thiazolidinediones (TZDs), metformin, antihyperlipidemics and vitamin E, but more data is needed as to whether it can prevent disease progression. A large trial on pioglitazone and Vitamin E is currently in progress by investigators from the NASH Clinical Research Network. The results will be out soon and are expected to shed more light on the efficacy of treatment with these drugs.
Other novel treatments that are still under investigation include: Anti- TNF agents and Angiotensin Receptor Blockers ( ARB ).
Research trials are underway to evaluate treatment of NAFLD and NASH.
At this moment there is no medical treatment or drug that can undo fatty liver disease.. As mentioned, a few studies have suggested that weight loss can help reduce the fat within the liver. Therefore, the most important advice for people with fatty liver is to lose weight if they are overweight or obese, increase their physical activity, follow a balanced diet and avoid alcohol and unnecessary medications. In patients with NASH, the more severe form of NAFLD,the same guidance holds.. It is also important to control blood sugars and treat high cholesterol levels when appropriate.
Research trials are underway to develop drugs for NAFLD and NASH.
How can NAFLD/NASH be prevented?
To reduce your risk of nonalcoholic fatty liver disease, try to:
- Choose a healthy diet
- Maintain a healthy weight
- Avoid excess alcohol
- Avoid certain medication
* One drink is 1/2oz of pure 100% alcohol. That is one 12 oz beer, 1.5oz of liquor, or 4oz of wine.