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INTRODUCTION

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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. Nonalcoholic fatty liver disease (NAFLD) is an umbrella term describing a spectrum of liver abnormalities from bland steatosis to hepatocellular injury, fibrosis, and even cirrhosis, resulting from fat accumulation. Nonalcoholic steatohepatitis (NASH) is a subtype of NAFLD characterized by steatosis, ballooning hepatocyte degeneration, and inflammation (Fig. 421-1). A large variety of acquired and inherited conditions can result in fatty liver disease (Table 421-1), but by far, the most common cause in the pediatric population is related to overweight and obesity. In the United States, 69% of adults and 30% of children are overweight or obese (see also Chapter 24). As the prevalence of obesity has increased, so has the prevalence of comorbid diseases, such as NAFLD. NASH was first reported by Ludwig and colleagues in 1980, when they described hepatic histologic findings similar to alcoholic steatohepatitis in adults not consuming significant amounts of alcohol. In 1983, Moran, and colleagues described NASH in obese children. Although bland steatosis alone is thought to be nonprogressive, or very slowly progressive, NASH can progress to cirrhosis, and NASH-related cirrhosis has been reported in children as young as 10 years of age. 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.

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Figure 421-1

The liver in a patient with nonalcoholic fatty liver disease (NAFLD). The liver has prominent macrovesicular steatosis (white/clear round spaces) and mild fibrosis. (Masson trichrome stain.)

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Table Graphic Jump Location
Table 421-1CAUSES OF NONALCOHOLIC FATTY LIVER DISEASE AND NONALCOHOLIC STEATOHEPATITIS
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EPIDEMIOLOGY

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Because NAFLD is a histologic diagnosis and most people with the disease are clinically asymptomatic, autopsy studies ...

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