What does liver elastography diagnose?

What Liver Elastography Diagnoses

Liver elastography diagnoses and stages liver fibrosis and cirrhosis in patients with chronic liver disease by measuring liver stiffness as a surrogate biomarker for fibrosis burden. 1, 2

Primary Diagnostic Applications

Elastography is used to noninvasively assess:

• Liver fibrosis staging - The technique distinguishes between stages of fibrosis (F0-F4) in chronic liver disease, with highest accuracy for detecting cirrhosis (F4) where sensitivity reaches 87-91% and specificity 91% 1
• Cirrhosis detection - Vibration-controlled transient elastography (VCTE) demonstrates sensitivity of 89% and specificity of 91% for diagnosing cirrhosis across multiple etiologies 2
• Significant fibrosis (≥F2) - VCTE has 70% sensitivity and 84% specificity for detecting significant fibrosis, which determines need for treatment in many liver diseases 1

Disease-Specific Diagnostic Thresholds

Chronic Hepatitis C and B

• Significant fibrosis (≥F2): Use cutoff >7.0 kPa 3
• Cirrhosis (F4): Use cutoff >12.5 kPa 3
• These thresholds guide antiviral therapy decisions in patients with chronic viral hepatitis 1

Non-Alcoholic Fatty Liver Disease (NAFLD)

• Rule out advanced fibrosis: <8.0 kPa has 93% sensitivity to exclude advanced fibrosis 3
• Detect significant fibrosis: Optimal cutoff is 8.2 kPa 3
• The American Gastroenterological Association makes no firm recommendation for NAFLD due to evidence limitations, but elastography is widely used after indeterminate FIB-4 scores (1.3-3.25) 1, 3

Alcoholic Liver Disease

• Rule out advanced fibrosis: <8.0 kPa reliably excludes advanced fibrosis 3
• Diagnose cirrhosis: Use cutoff of 12.5 kPa with pooled sensitivity 95% and specificity 71% 1
• Elastography should be performed immediately in patients drinking at harmful levels (≥35 units/week for women, ≥50 units/week for men) 3

Beyond Fibrosis: Additional Diagnostic Capabilities

Portal Hypertension Assessment

• Clinically significant portal hypertension (CSPH): Liver stiffness >20-25 kPa diagnoses CSPH with AUROC of 0.93 3
• High-risk esophageal varices: Cutoff of 19.5 (±2) kPa helps rule out high-risk varices, potentially obviating routine endoscopic screening 1
• Liver stiffness ≥21 kPa predicts clinical decompensation events as effectively as hepatic venous pressure gradient ≥10 mmHg 3

Prognostic Information

• Elastography predicts liver decompensation risk and clinical outcomes in patients with cirrhosis 2
• Serial measurements allow treatment surveillance, continuous risk stratification, and monitoring of complications 4

Technical Modalities and Their Diagnostic Roles

Transient Elastography (TE/VCTE)

• Most commonly used and heavily validated method 1
• Performed with FibroScan device at point of care 1
• Requires ≥10 valid measurements with success rate ≥60% and interquartile range <30% of median value for reliability 3, 2

Acoustic Radiation Force Impulse (ARFI)/Point Shear Wave Elastography

• Can be combined with conventional ultrasound 1
• Superior in patients with obesity, ascites, and NAFLD compared to TE 1
• Unreliable examination rates three times lower than TE (2.1% vs 6.6%, P<.001) 1

Magnetic Resonance Elastography (MRE)

• Most accurate method for detecting and staging liver fibrosis 2, 5
• Permits assessment of whole liver rather than limited sampling area 2
• Particularly useful when ultrasound-based methods fail or are unreliable 5

Critical Confounding Factors That Affect Diagnosis

Elastography measures liver stiffness, which can be falsely elevated by factors other than fibrosis: 1, 2

• Active inflammation/hepatitis - Significantly increases stiffness independent of fibrosis 1, 2, 6
• Elevated ALT levels - Patients with ALT >80-120 IU/L can have stiffness in cirrhosis range despite minimal fibrosis (odds ratio 3.84-4.10) 6
• Recent food intake - Increases hepatic blood flow and falsely elevates measurements; patients must fast ≥4 hours before examination 3, 2
• Extrahepatic cholestasis - Causes falsely elevated stiffness 1, 2
• Passive congestion - From heart failure or hepatic vein obstruction 1, 2
• Recent alcohol consumption - Should ideally test after 2 weeks of abstinence 3
• Edema - Increases measured stiffness 1

Technical Limitations Affecting Diagnostic Accuracy

Patient Factors

• Obesity - TE unreliable in patients with BMI >28 kg/m², though extra-large probe now available 1, 2
• Ascites - TE cannot be performed reliably 1, 2
• Narrow intercostal spaces - Limits probe placement 2
• Failure rates: 1.1-3.5% in Asian populations, 4.3-10.5% in Western populations 2

Disease-Specific Limitations

• Cannot distinguish intermediate fibrosis stages - TE performs poorly at differentiating F2 vs F3 1
• Subject to sampling error - Similar to liver biopsy limitations, though less severe 1
• Cannot diagnose etiology - Only measures stiffness, not the cause of liver disease 3

Clinical Algorithm for Elastography Use

Step 1: Initial Risk Stratification

• Calculate FIB-4 score first in all adults with NAFLD using routine labs (AST, ALT, platelet count, age) 3
• For viral hepatitis, proceed directly to elastography for treatment decisions 1
• For alcohol-related disease, perform elastography immediately if drinking at harmful levels 3

Step 2: Elastography Indications

• NAFLD: FIB-4 ≥1.3 (or ≥2.0 if age ≥65 years) 3
• Chronic hepatitis B/C: All patients to guide antiviral therapy 1, 3
• Alcoholic liver disease: Harmful alcohol use or any suspicion of advanced disease 1, 3

Step 3: Result Interpretation

• <8.0 kPa: Rules out advanced fibrosis; repeat in 2-3 years if risk factors persist 3
• 8.0-12.5 kPa: Significant fibrosis; requires hepatology evaluation and treatment consideration 3

• 12.5 kPa: Cirrhosis; requires urgent hepatology referral, HCC screening, and variceal screening 3

• 20-25 kPa: Clinically significant portal hypertension; requires endoscopic variceal screening 3

Step 4: Ensure Technical Validity

• Verify ≥10 successful measurements obtained 3, 2
• Success rate ≥60% 3, 2
• Interquartile range <30% of median value 3, 2
• If criteria not met, result is unreliable and alternative assessment needed 3

Common Diagnostic Pitfalls to Avoid

• Do not rely on elastography alone - Cannot diagnose etiology or exclude other causes of liver disease 3
• Check ALT before interpretation - Elevated ALT (>80 IU/L) can cause stiffness in cirrhosis range despite minimal fibrosis 6
• Ensure proper fasting - Non-fasting studies are unreliable 3, 2
• Consider inflammation status - Active hepatitis falsely elevates stiffness; grade 3 inflammation has odds ratio of 9.10 for falsely suggesting cirrhosis 6
• Verify technical quality - Invalid measurements (success rate <60%, IQR >30%) should not be used for clinical decisions 3, 2
• Do not use during acute illness - Avoid during acute hepatitis, recent alcohol use, or cholestasis 3, 2
• Recognize morphologic features - Ultrasound findings of cirrhosis (nodular surface, caudate hypertrophy, splenomegaly) are subjective and present only in later stages 1