Introductory Chapter: Nonalcoholic Fatty Liver Disease - What Should We Know?

Nonalcoholic fatty liver disease (NAFLD) is considered a major challenge because of its prevalence, difficulties in diagnosis, complex pathogenesis, and lack of approved therapies. It will become the main cause of chronic liver disease in adults and children and the leading indication for liver transplantation (LT) in the next decades replacing hepatitis C virus (HCV) infection [1]. It is characterized by excessive hepatic fat accumulation, associated with insulin resistance (IR), where liver pathology shows steatosis in >5% of hepatocytes or a proton density fat fraction >5.6% assessed by proton magnetic resonance spectroscopy (1HMRS) or quantitative fat/water selective magnetic resonance imaging (MRI) [2]. It represents a group of conditions ranging from simple asymptomatic liver steatosis (nonalcoholic fatty liver (NAFL)) (known by imaging or histology) to cirrhosis (nonalcoholic steatohepatitis (NASH) or cryptogenic), end stage liver disease (ESLD), and hepatocellular carcinoma (HCC), passing through nonalcoholic steatohepatitis (NASH), which is characterized by the presence of apoptosis, ballooning, inflammation, and fibrosis with the absence of secondary causes of hepatic fat accumulation such as significant alcohol consumption or viral infection [3]. In the majority of patients, NAFLD is commonly associated with metabolic comorbidities such as obesity, type 2 DM (T2DM), and dyslipidemia. So it became common after increased prevalence of these comorbidities [4]. Our book discusses some new topics related to NAFLD, where we divided it into four sectors: the first sector includes introductory chapter about NAFLD; the second sector contains experimental work related to the disease, while the third sector discusses diseases related to NAFLD; and finally the fourth sector includes a new noninvasive tool to diagnose NAFLD. The book gives hints regarding NAFLD prevalence, etiology, pathogenesis, pathology, diagnosis, and treatment. This introductory chapter discusses the recent updated data on the prevalence, natural history, pathophysiology, pathology, diagnosis, and treatment of the disease.