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Fatty liver disease describes the accumulation of excess fat
in liver cells. Fatty liver may cause no damage but in some cases
the excess fat leads to inflammation in the liver, known as steatohepatitis.
In adults, fatty liver has traditionally been most frequently associated
with alcohol ingestion. Therefore, the term nonalcoholic is
used to differentiate the disorders described in this section from alcohol-induced
fatty liver. Non-alcoholic fatty liver disease (NAFLD) is
an umbrella term describing a range of abnormalities from simple
steatosis to cellular injury, fibrosis, and even cirrhosis resulting from
fat accumulation. Non-alcoholic steatohepatitis (NASH) is
a subtype of NAFLD that includes steatosis, ballooning degeneration,
and inflammation. A large variety of acquired conditions can result
in fatty liver disease (see Table 426-1)
but by far the most common cause in the pediatric population is overweight
and obesity. In the United States, about two-thirds of adults are
overweight or obese, and 31.9% of children are overweight
or obese (see also Chapter 32).1As
the prevalence of obesity has increased, so has the prevalence of
comorbid diseases, such as nonalcoholic fatty liver disease (NAFLD). NASH
was first reported by Ludwig and colleagues2 in
1980, when they described a combination of histologic findings similar
to alcoholic steatohepatitis in adults not consuming significant
amounts of alcohol. In 1983, Moran, and colleagues3 described
NASH in obese children. Although steatosis alone has not been shown
to progress to cirrhosis, NASH can progress to cirrhosis, and NASH-related
cirrhosis has been reported in children as young as 10 years of
age.4 Currently, NAFLD is considered to be the
most common reason for unexplained abnormal liver tests in the pediatric
population and the most common chronic liver disease in the Western
world.5
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Because nonalcoholic fatty liver disease (NAFLD) is truly a histologic
diagnosis and most people with the disease are clinically asymptomatic,
autopsy studies are best designed to assess the prevalence of NAFLD
and nonalcoholic steatohepatitis (NASH). In 1990, Wanless and Lentz6 reported
that 70% of obese adults have steatosis compared to 35% of lean
adults, and 18.5% of ...