Non-alcoholic fatty liver disease: a practical approach to diagnosis and staging

Non-alcoholic fatty liver disease (NAFLD) is now the commonest cause of abnormal liver function tests (LFTs) in the UK with approximately a third of the population being affected. The exact prevalence is not known, but population studies from the USA and China using magnetic resonance spectroscopy estimate that approximately 30% of the general population have steatosis. It is a spectrum of disease ranging from simple steatosis, to non-alcoholic steatohepatitis (NASH), through to advanced fibrosis and cirrhosis. The majority have simple steatosis, but approximately 10-30% develop NASH and the development of NASH cirrhosis is associated with a poor long-term prognosis. Patients with NASH have increased liver-related and cardiovascular mortality. Many patients with NAFLD remain undiagnosed, and recognising those at risk is the first step. Clinicians overly rely on abnormal liver enzymes to identify patients with NAFLD, so patients with significant liver disease can be overlooked, potentially missing opportunities for intervention. Although liver biopsy is the gold standard method for diagnosing and staging NAFLD, the majority of patients can be effectively diagnosed non-invasively with tests that are routinely available in the clinic today. This review discusses a pragmatic approach to diagnosis and staging of NAFLD so that patients at the highest risk of liver-related complications can be identified.