Fatty Liver (cont.)
In this Article
Are there other causes of fat accumulation in the liver?
Indeed, there are
many other causes of fat accumulation in the liver besides NAFLD. However, NAFLD
and NASH are considered the primary fatty liver diseases. The secondary fatty
liver diseases include those that occur in other types of liver disease. Thus,
alcoholic liver disease (ALD) is the most frequent secondary fatty liver
disease. Secondary fatty liver can also occur in chronic viral hepatitis C (HCV),
chronic viral hepatitis B (HBV), chronic autoimmune hepatitis (AIH), and Wilson's
disease. (In AIH, the body's immune defense system mistakenly attacks its own
liver. In Wilson's disease, an accumulation of copper injures the liver.) In
all of these secondary fatty liver diseases, fatty liver is associated with
other liver abnormalities distinct from NAFLD and is thought to result from
liver cell injury.
Another type of secondary fatty liver disease is unrelated to other specific
liver diseases. In these cases, the accumulation of liver fat is due to
disturbances in the body's processing (metabolism) of fat (lipid) rather than
to direct injury to the liver cells. Such causes include certain drugs (e.g.,
prednisone), some gastrointestinal operations (bariatric surgery) for obesity,
malnutrition, and genetic defects in proteins that process (metabolize) lipids.
As described below, all of the secondary causes of fatty liver disease must be
ruled out before attempting to establish the diagnosis of NAFLD. This is why
NAFLD is considered a diagnosis of exclusion.
How long have we known about NAFLD and NASH?
Liver specialists (hepatologists)
actually recognized what is now called NASH in the 1970's, but it was
described under different names. In 1980, Dr. J. Ludwig from the Mayo Clinic in
Rochester, Minnesota made an astute observation. He noted that certain
individuals who share common features (obesity, diabetes, and elevated
cholesterol) had a liver disease that closely resembled alcoholic liver disease
(ALD). However, these patients drank no alcohol whatsoever. So, Dr. Ludwig was
the first to coin the term nonalcoholic steatohepatitis (NASH). For many years,
however, NASH was thought by most doctors to be a totally harmless condition.
Or, it was considered an innocent bystander that was associated with other liver
diseases (especially viral hepatitis). In fact, during those years, simple fatty
liver (steatosis) and NASH were considered to be equivalent processes.
The discovery of the hepatitis C virus (HCV) played an accidental role in the
recognition of the clinical significance of NASH. Up until 1990, individuals who
had hepatitis with signs similar to those of viral hepatitis A or B (but with
negative blood tests for both) were said to have non-A-non-B viral hepatitis.
Then, in 1990 the hepatitis C virus was discovered. In the years that followed,
the ways by which HCV is spread (blood transfusion and intravenous drug use) and
its effects on the liver were recognized. It turned out that a great majority of
non-A-non-B viral hepatitis cases were in fact due to HCV. There remained,
however, some individuals whose tests were negative for HCV as well as for other
types of liver disease. Only then did researchers realize that for many of these
individuals, NASH was the culprit. This realization has since led to a flurry of
interest and research regarding NASH and to the understanding that it is not a
harmless condition.
Clinical studies and basic research on NAFLD are still in their infancy as
compared to other common liver diseases, such as ALD and HCV. As a result, we
continue to have an incomplete understanding of the natural history of NAFLD.
Moreover, we do not know much about the processes responsible for the
progression from simple fatty liver to NASH and NASH to cirrhosis.
Next: How common are NAFLD and NASH and who are at risk? »
- Statins - Read about statins, cholesterol lowering medications like Levacor, Zocor, Pravachol, Lipitor, Crestor, and more. Side effects, drug interactions, and patient information is also provided.
- Liver Blood Tests - Learn about liver blood tests used to detect liver damage disease such as fatty liver, cirrhosis, hepatitis, Tylenol liver damage, and more. This includes measuring the aminotransferases enzymes (AST and ALT levels)
- Abdominal Pain - Learn about abdominal pain (pain in the stomach / abdomen) including causes, symptoms, how abdominal pain is diagnosed, and how abdominal pain is treated.
Latest Medical News
Digestion RSS