[Ultrasonography in the diagnosis of nonalcoholic fatty liver disease]

Abstract

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in Western countries. Although no specific studies have been performed, the estimated prevalence of NAFLD in Croatia correlates with the prevalence in other countries, ranging from 20% to 40%. It encompasses a histological spectrum that ranges from simple steatosis to steatohepatitis, which can progress to cirrhosis in up to 20% of patients. Unfortunately, accurate noninvasive modalities for diagnosing nonalcoholic steatohepatitis (NASH) and monitoring disease progression or regression are unavailable. Therefore, liver biopsy remains the gold standard in diagnosing NASH but it is also associated with risks and possible sampling errors. Since liver biopsy cannot be performed as a screening method to detect NAFLD in general population, abdominal ultrasonography as a noninvasive modality has been widely used. Although sonographic characteristics of NAFLD were first described 20 years ago, larger studies have been conducted over the past few years as a result of the rising interest in NAFLD among investigators. The aim of these studies was to simplify the diagnosis of NASH. Abdominal ultrasonography has been shown to have a sensitivity of 60%-94% and specificity of 84%-95% for detecting fatty liver and it is used as a screening method in patients with incidental elevation of liver enzymes. Ultrasonographic scoring system developed by Hamaguchi et al. included hepatorenal echo contrast, liver brightness, deep attenuation, and vascular blurring. Score > or = 2 corresponded to NAFLD with a high, 92% sensitivity and 100% specificity, and a high level of intraobserver reliability.The inability to distinguish different forms of NAFLD and staging hepatic fibrosis limits the use of ultrasonography as a stand alone modality for detecting NAFLD. In the future, serum markers together with advancements in imaging modalities may potentially diminish or obviate the need of liver biopsy.