Pediatric nonalcoholic fatty liver disease (NAFLD) was first reported in 1983.  It is currently the primary form of liver disease among children.  NAFLD has been associated with the metabolic syndrome, which is a cluster of risk factors that contribute to the development of cardiovascular disease and type 2 diabetes mellitus. Studies have demonstrated that abdominal obesity and insulin-resistance in particular are thought to be key contributors to the development of NAFLD.      Because obesity is becoming an increasingly common problem worldwide, the prevalence of NAFLD has been increasing concurrently.  Moreover, boys are more likely to be diagnosed with NAFLD than girls with a ratio of 2:1.   Studies have suggested that progression toward a more advance stage of disease among children is dependent on age and presence of obesity.  This finding is consistent with previous studies in adults demonstrating the same association between age and obesity, and liver fibrosis.   Early diagnosis of NAFLD in children may help prevent the development of liver disease during adulthood.   This is challenging as most children with NAFLD are asymptomatic with few showing abdominal pain.  Currently, liver biopsy is considered the gold standard for diagnosing NAFLD.  However, this method is invasive, costly and bears greater risk for children, and noninvasive screening and diagnosing methods would have significant public health implications for children with NAFLD.  The only treatment shown to be truly effective in childhood NAFLD is weight loss.  
The other source of blood for the liver is the portal vein, supplying 2/3 of the blood that flows into the liver. The nutrients in the portal vein originate from the digestive tract, this time, not the heart, like the hepatic artery does. In essence, raw food that is absorbed from the intestines flows directly to the liver. This exposes the liver to toxins and bacteria, which are metabolized and detoxified by a normal liver before they leave the liver and enter the general circulation via the heart. This detoxification process protects other organs, particularly the brain, from bacteria and toxins that could injure brain cells. When this system fails, which happens in liver shunts, excess ammonia will build up in the bloodstream and affect the brain.