Fatty Liver Identified — Steatosis on Imaging or Labs
Fat accumulation in the liver is common, but its cause is not obvious.
- ~32%: Global fatty liver prevalence (of adults worldwide)
- >5%: Liver fat threshold (hepatocytes with steatosis)
- ~85%: Ultrasound sensitivity (for moderate-severe fat)
- 2 main: Etiologies to separate (alcoholic vs metabolic)
Steatosis is a shared endpoint
Many different causes converge on the same fatty liver appearance.
Imaging cannot distinguish cause
Ultrasound and CT show fat, not why it accumulated.
History and labs decide etiology
Alcohol intake and metabolic risk factors must be assessed next.
Alcohol History Assessed — Quantity and Frequency of Use
A careful alcohol history is the single most decisive diagnostic step.
- >21: Risk threshold, men (units/week for ALD risk)
- >14: Risk threshold, women (units/week for ALD risk)
- >60g/day: Heavy drinking cutoff (sustained, men)
- ~30-50%: Self-report underestimation (common in ALD patients)
Quantity defines the label
Consistent heavy drinking points strongly toward alcoholic fatty liver.
Frequency matters as much as volume
Daily moderate drinking can outweigh occasional binges.
Collateral history helps verify
Family or partner reports often reveal underreported intake.
Metabolic Risk Factors Assessed — Obesity, Diabetes, Dyslipidemia
Metabolic syndrome components push the diagnosis toward metabolic fatty liver.
- ~80%: Obesity in MASLD (of diagnosed patients)
- ~55%: Type 2 diabetes overlap (of MASLD patients)
- ≥3 of 5: Metabolic syndrome criteria (components required)
- ~70%: Dyslipidemia prevalence (in MASLD cohorts)
Central obesity raises suspicion
Waist circumference and BMI are quick first screens.
Insulin resistance drives fat storage
Diabetes or prediabetes strongly favors metabolic etiology.
Lipid panel adds evidence
High triglycerides and low HDL support metabolic disease.
Lab Marker Pattern — AST/ALT Ratio and GGT Level
Enzyme ratios add objective evidence to the clinical picture.
- Alcoholic: AST/ALT >2 suggests (classic ALD pattern)
- Metabolic: AST/ALT <1 suggests (typical MASLD pattern)
- 2-5×: GGT elevation in ALD (upper limit of normal)
- ~70%: GGT sensitivity alone (for heavy drinking)
AST/ALT ratio shifts with alcohol
Alcohol depletes hepatic ALT more than AST, raising the ratio.
GGT tracks alcohol exposure
GGT rises early and steeply with sustained drinking.
Markers are supportive, not definitive
No single lab value confirms etiology alone.
Differential Classification — Alcoholic, Metabolic, or Combined
History, risk factors, and labs are weighed together for a final call.
- ~20-30%: Combined etiology cases (both factors present)
- Reduced: Misclassification risk (with full triad assessment)
- Ambiguous: Biopsy reserved for (or discordant cases)
- High: Management divergence (abstinence vs metabolic care)
Weigh all three data streams
History, risk factors, and labs together outperform any single clue.
Combined etiology is common
Many patients carry both alcohol and metabolic contributions.
Classification guides treatment
Abstinence counseling differs sharply from metabolic management.