Here are large lipid vacuoles within hepatocytes in a case of macrovesicular steatosis (fatty change). The lipid accumulates when lipoprotein transport is disrupted and/or when fatty acids accumulate. Alcohol (ethanol), for example, is a hepatotoxin that interferes with mitochondrial and microsomal function in hepatocytes, leading to an accumulation of lipid.

The definitive diagnosis of non-alcoholic liver disease (NAFLD) steatosis is liver biopsy, but this is uncommonly done because a good history and physical examination will provide clues in most cases. An overweight person (even a child) with a mild to moderately elevated serum alanine transferase (ALT) is suggestive, in the absence of drug usage or causes for hepatitis. Right upper quadrant pain may be present from liver enlargement. Imaging studies include ultrasound examination, with diffusely increased echogenicity, or CT scan showing diffusely decreased attenuation, are supportive evidence for NAFLD.