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Liver steatosis
Hepatic steatosis, also known as fatty liver disease, refers to abnormal accumulation of fat within hepatocytes, most commonly manifesting as non-alcoholic fatty liver disease (NAFLD).1)
Epidemiology
Hepatic steatosis affects up to 30% of the general population in Western countries, with rising prevalence linked to obesity, diabetes, and metabolic syndrome.2) Prevalence exceeds 70% in patients with type 2 diabetes and reaches 90% in those undergoing bariatric surgery. Risk factors include insulin resistance, hyperlipidemia, rapid weight loss, total parenteral nutrition, and certain medications.
Clinical presentation
Most cases remain asymptomatic and are detected incidentally on ultrasound or other imaging.3) Symptomatic patients may report right upper quadrant discomfort, fatigue, or elevated liver enzymes. Advanced disease can progress to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, or hepatocellular carcinoma.
Pathology
Steatosis results from impaired fat metabolism, with triglycerides accumulating in >5% of hepatocytes.4) Macrovesicular steatosis predominates, featuring a single large cytoplasmic fat droplet displacing the nucleus; microvesicular involves multiple small droplets.5)
Radiographic features
Ultrasonography
* Hyperechoic liver parenchyma (”bright liver”) compared to kidney or spleen * Grading:
| Grade | Features |
|---|---|
| Mild | Slight echogenicity increase |
| Moderate | Impaired vessel wall visualization |
| Severe | Poor diaphragm/portal vein visibility 6) |
Advanced techniques quantify via attenuation imaging or backscatter coefficient.
Computed tomography
* Unenhanced CT: Liver attenuation <40 HU absolute or >10 HU lower than spleen 7) * Contrast-enhanced: Focal sparing appears hyperdense relative to steatotic parenchyma (gallbladder fossa, segment IV) 8)
Magnetic resonance imaging
* Chemical shift imaging (in/out-of-phase): Signal dropout on opposed-phase images (>5% fat) * Proton density fat fraction (PDFF): Gold standard for quantification 9)
Treatment and prognosis
Management targets underlying causes (weight loss, diabetes control). Steatosis alone carries excellent prognosis without fibrosis; NASH risks progression to cirrhosis (20-30%).10)
Differential diagnosis
* Glycogen storage disease (US: hyperechoic but vessels clear)11) * Acute hepatitis (diffuse hypoechoic)12) * Focal fat sparing/deposition mimics mass * Iron overload (high attenuation on CT)