Focal Fatty Liver Infiltration: Causes, Significance, and Management

Focal fatty infiltration (FFI) is localized hepatic steatosis, often perivascular (portal vein branches) or geographic, seen on US/CT/MRI.

Common Causes

• Metabolic: Insulin resistance, obesity, diabetes, dyslipidemia (most common).
• Alcohol: Perivenular (zone 3) steatosis; FFI can be early sign.
• Medications: Corticosteroids, tamoxifen, methotrexate, amiodarone, irinotecan.
• Vascular: Portal vein thrombosis/atresia → arterial perfusion of segment → fatty change.
• Viral: HCV genotype 3 (direct steatogenic effect).
• Genetic: PNPLA3, TM6SF2 variants.

Imaging Features

• US: Geographic hyperechoic area, sharp margins, no mass effect, posterior acoustic enhancement.
• CT: Geographic hypoattenuation (-10 to -50 HU vs. spleen), no mass effect.
• MRI: Signal drop on opposed-phase chemical shift (gold standard).

Clinical Significance

Usually benign, reversible. But:

• May mimic mass (pseudolesion) → unnecessary biopsy.
• Can coexist with focal sparing (mimics tumor).
• If diffuse + FFI → higher NASH/fibrosis risk.

Management

• Treat metabolic drivers: weight loss 7–10%, glycemic control, lipid management.
• Alcohol cessation.
• Medication review.
• Follow-up imaging if diagnostic uncertainty or monitoring NASH.