(ASH) or non-alcoholic steatohepatitis (NASH) depends on the persistence or severity of the inciting cause. Pathological lesions in both conditions are similar. However, the extent of inflammatory response varies widely and does not always correlate with degree of fat accumulation. Steatosis (retention of lipid) and onset of steatohepatitis may represent successive stages in FLD progression. Liver disease with extensive inflammation and a high degree of steatosis often progresses to more severe forms of the disease. Hepatocyte ballooning and necrosis of varying degrees are often present at this stage. Liver cell death and inflammatory responses lead to the activation of hepatic stellate cells, which play a pivotal role in hepatic fibrosis. The extent of fibrosis varies widely. Perisinusoidal fibrosis is most common, especially in adults, and predominates in zone 3 around the terminal hepatic veins. The progression to cirrhosis may be influenced by the amount of fat and degree of steatohepatitis and by a variety of other sensitizing factors. In alcoholic FLD, the transition to cirrhosis related to continued alcohol consumption is well-documented, but the process involved in non-alcoholic FLD is less clear. Diagnosis Most individuals are asymptomatic and are usually discovered incidentally because of abnormal liver function tests or hepatomegaly noted in unrelated medical conditions. Elevated liver enzymes are found in 50% of patients with simple steatosis. The serum alanine transaminase (ALT) level usually is greater than the aspartate transaminase (AST) level in the nonalcoholic variant and the opposite in alcoholic FLD (AST:ALT more than 2:1). Simple blood test may help to determine the magnitude of the disease by assessing the degree of liver fibrosis. For example, AST-to-platelets ratio index (APRI score) and several other score, calculated from the results of blood test, can detect the degree of liver fibrosis and predict the future formation of liver cancer. Imaging studies are often obtained during the evaluation process. Ultrasonography reveals a "bright" liver with increased echogenicity. Medical imaging can aid in diagnosis of fatty liver; fatty livers have lower density than spleens on computed tomography (CT), and fat appears bright in T1-weighted magnetic resonance images (MRIs). Magnetic resonance elastography, a variant of magnetic resonance imaging, is investigated as a non-invasive method to diagnose fibrosis progression. Histological diagnosis by liver biopsy is the most accurate measure of fibrosis and liver fat progression as of 2018. Conventional imaging methods, such as ultrasound, CT and MRI, are not specific enough to detect fatty liver