Steatosis

Steatosis, also known as hepatic steatosis or fatty liver, is the abnormal accumulation of triglycerides within hepatocytes. It is a histological finding rather than a diagnosis on its own and may be reversible if the underlying cause is addressed. The term encompasses several patterns of fat storage in the liver.

There are two major histologic patterns: macrovesicular steatosis, in which large fat droplets displace the nucleus, and microvesicular steatosis, in which many small droplets accumulate with a preserved or minimally displaced nucleus. Macrovesicular steatosis is the most common form in adults, while microvesicular steatosis is seen in certain drug toxicities, mitochondrial disorders, pregnancy-related conditions, and Reye syndrome.

Steatosis arises from imbalances in fat accumulation and removal within the liver. The most common causes are alcohol-related liver disease and nonalcoholic fatty liver disease (NAFLD). NAFLD is strongly associated with obesity, insulin resistance, type 2 diabetes, dyslipidemia, and metabolic syndrome. Other causes include medications (such as methotrexate, amiodarone, steroids), nutritional disorders, rapid weight loss, viral hepatitis, pregnancy, and certain genetic or mitochondrial conditions.

Clinically, steatosis is often asymptomatic and discovered incidentally. When present, patients may have hepatomegaly or mild elevations in liver enzymes. NAFLD can progress to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Diagnosis typically involves imaging (ultrasound, CT, MRI) showing hepatic fat and laboratory evaluation to exclude other causes; liver biopsy can distinguish simple steatosis from steatohepatitis and stage fibrosis, though it is not always required.

Management focuses on treating or removing the underlying cause, especially weight loss, physical activity, and control of metabolic risk factors. Abstinence from alcohol is essential in alcohol-related disease. No universally approved pharmacologic therapy exists for NAFLD, though lifestyle changes and certain agents may be used in specific cases. Steatosis can be reversible, but progression to advanced liver disease is a potential risk if underlying factors persist.