Definition of fatty liver
There are two types of fatty liver disease- the alcoholic fatty liver disease and the nonalcoholic fatty liver disease. The disease process is however the same in both these types of fatty liver disease.
Fat accumulation in the liver cells is called steatosis. If fat accumulation in the liver cells is associated with inflammation it is called steatohepatitis.
The fat content of normal liver is about 1.5% of its weight. In fatty liver, fat accumulation of more than 5-10% by weight is seen. Fatty liver can be a diffuse fatty liver or a focal fatty liver. Diffuse fatty liver is seen in most of the cases.
Fatty liver is not a disease by itself. It is a manifestation of diverse disease processes. If the underlying cause is treated, then the fat accumulation in the liver cells disappears. If it is not treated, then it proceeds in to more severe forms of liver disease like steatohepatitis in which there is inflammation of the liver cells, cirrhosis in which scar tissue is formed in the liver with liver failure and very rarely liver cancer.
Fatty liver can be microvesicular or macrovesicular fatty liver. In microvesicular fatty liver the fat droplets are smaller and in macrovesicular the fat droplets are larger.
What happens in fatty liver?
Liver is the largest gland in the body. It is associated with diverse functions like synthesis, detoxification, excretion and storage. Because of its diverse functions, it is involved in a number of disease conditions especially those involving metabolism.
Fatty liver occurs
• When there is increased transfer of fat to liver from other parts of the body
• When there is increased extraction of fat presented by the intestine
• When there is decreased breakdown of fat and its removal from the liver
Causes of fatty liver
Fatty liver is broadly classified in to alcoholic fatty liver disease and nonalcoholic fatty liver disease.
Alcoholic fatty liver occurs in heavy drinkers. In those who drink alcohol, fat accumulation in the liver cells is the earliest manifestation. Fat accumulation in the liver cells is seen in 90% of heavy drinkers. It is a reversible condition and usually is quickly reversible with abstinence. With continued alcohol abuse, inflammation and scar tissue forms leading to cirrhosis which is irreversible. Over a period of time cirrhosis leads to liver cancer.
Nonalcoholic fatty liver is more common than alcoholic fatty liver. Nonalcoholic fatty liver is not due to any specific cause and it occurs due to diverse causes. The causes of nonalcoholic liver disease may be divided broadly in to those due to drugs and toxins and those due to metabolic abnormalities. Some of the conditions which are associated with nonalcoholic fatty liver are-
• Diabetes mellitus
• Drugs including steroids, estrogens, certain anticancer drugs
• Inborn errors of metabolism
o Wilson disease
o Glycogen storage disease
• Surgical procedures
o Gastric bypass surgery
o Extensive small bowel resection
o Jejunoileal bypass surgery
o Industrial exposure to petrochemicals
o Inflammatory bowel disease
o Jejunal diverticulosis with bacterial overgrowth
o Severe anemia
o Total parenteral nutrition
Obesity is the condition most commonly associated with nonalcoholic fatty liver. Non alcoholic fatty liver may be seen in as many as 80% of obese individuals. More than the body mass index, it is the distribution of body fat that is important in the development of fatty liver. Intrabdominal or visceral fat is a more correlated with fatty liver.
Diabetes mellitus is the second most common condition associated with nonalcoholic fatty liver. Type 2 diabetes mellitus has been found in as many as 75% of those with nonalcoholic fatty liver. These individuals may or may not be obese. But if they are obese they are more associated with fatty liver.
Nonalcoholic fatty liver is now recognized as the liver component of metabolic syndrome. Metabolic syndrome includes –
• Glucose intolerance
The risk and severity of nonalcoholic fatty liver increase with the number of components of the metabolic syndrome.
Symptoms and diagnosis of fatty liver
Fatty liver is not associated with any symptoms. Fatty liver is usually diagnosed incidentally during medical tests done for other reasons. Ultrasound scan of the abdomen will show enlarged liver. Liver function test may sometimes show the levels of the liver enzymes higher than normal. The confirmative test is liver biopsy and it will show fat accumulation in liver cells.
Treatment of fatty liver
There is no specific medical or surgical treatment for fatty liver. The treatment of fatty liver depends on the underlying cause. If fatty liver is due to alcohol intake, abstinence would reverse the fat accumulation in liver cells. If it is nonalcoholic fatty liver the underlying cause is treated. The treatment for fat accumulation in liver cells include the following-
• Weight reduction - Since obesity is the most common factor associated with fatty liver, weight reduction should be done to reverse fatty liver. A body mass index less than 25 is considered appropriate. Dietary modification, exercise and medications are used to reduce weight. Losing one to two pounds per week should be the goal while considering weight reduction. The medication orlistat has been used for weight reduction. Bariatric surgery is done for morbid obesity.
• If the patient is a diabetic, effective control of blood glucose level would prevent fat accumulation in liver cells
• If the patient is having hyperlipidemia, control of blood cholesterol with dietary modifications and medications would prevent fat accumulation
• If fatty liver is due to medications, those medications should be stopped
• Lipid lowering medications and insulin sensitizers have been found to be effective in the treatment of fatty liver. These include-
o Metformin and Thiazolidinediones like pioglitazone ( insulin sensitizers)
o Gemfibrozil, Statins (lipid lowering agents)
• Medications like ursodeoxy cholic acid, Vitamin E, N acetyl cysteine have been found to be effective in the treatment of nonalcoholic fatty liver disease.