Liver Shear-Wave Elastography

Shear-wave elastography quantifies liver stiffness as a surrogate for hepatic fibrosis, providing a non-invasive alternative to biopsy for staging chronic liver disease and monitoring progression or regression. An acoustic push pulse generates shear waves whose propagation speed increases with tissue stiffness; the result is reported in kilopascals or metres per second alongside strict quality metrics.

Indications

Staging and monitoring of fibrosis in chronic viral hepatitis B and C
Assessment of non-alcoholic/metabolic-associated fatty liver disease (NAFLD/MASLD)
Alcohol-related and autoimmune liver disease evaluation
Risk stratification for clinically significant portal hypertension and varices
Follow-up of treatment response and disease progression

Contraindications & Cautions

Unreliable in acute hepatitis, hepatic congestion (right heart failure) and cholestasis, which falsely raise stiffness
Ascites prevents shear-wave transmission from an intercostal window
Non-fasting state, food and recent alcohol transiently increase stiffness
Narrow intercostal spaces, obesity and inadequate breath-hold degrade measurement quality

Patient Preparation

Fast for at least 4-6 hours to avoid postprandial elevation of stiffness
Rest supine for several minutes before measurement
Right arm in maximal abduction behind the head to widen the intercostal spaces
Neutral breath-hold (avoid deep inspiration or Valsalva which alter values)
Record relevant liver enzymes, aetiology and BMI as confounders

Technique & Parameters

Curvilinear 1-6 MHz probe with 2D shear-wave or point shear-wave elastography
Intercostal approach through the right hepatic lobe (segments 5/8)
Place the region of interest at least 1.5-2 cm below the liver capsule, avoiding large vessels, ducts and rib shadowing
Acquire during a short neutral breath-hold with the probe perpendicular to the capsule
Obtain at least 10 valid measurements and report the median
Ensure quality: interquartile range/median ratio below 30% (below 15% for point SWE)

Systematic Review

Confirm adequate fasting, positioning and breath-hold before acquiring
Verify ROI depth, vessel-free placement and stable shear-wave map/propagation pattern
Assess measurement reliability using IQR/median and number of valid acquisitions
Interpret stiffness against system- and aetiology-specific thresholds
Correlate with grey-scale morphology, spleen size and Doppler signs of portal hypertension
Exclude confounders (congestion, inflammation, cholestasis, food) before staging

Key Findings & Significance

Rising liver stiffness (kPa) correlates with advancing fibrosis stage from F0 to F4
Values around or below ~5-6 kPa typically indicate absent or minimal fibrosis
Progressive elevation supports significant fibrosis (>=F2) and advanced fibrosis/cirrhosis (F3-F4)
Marked elevation raises concern for cirrhosis and clinically significant portal hypertension
High IQR/median or few valid measurements indicates an unreliable, non-diagnostic result
Discordantly high values in acute hepatitis or congestion reflect confounders, not fibrosis

Differential Considerations

Elevated stiffness: true fibrosis vs acute inflammation vs hepatic congestion vs cholestasis vs infiltration
Aetiology-specific thresholds differ (e.g. viral hepatitis vs MASLD), so cut-offs are not interchangeable
System dependence: values in kPa/m per second vary between transient elastography and 2D SWE vendors
Focal high stiffness within a mass suggests malignancy rather than diffuse fibrosis
Unreliable result: technical failure vs ascites vs narrow window vs poor breath-hold

Pearls & Pitfalls

Fasting and neutral breath-hold are essential; postprandial and deep-inspiration values are falsely high
Always report the aetiology and the specific system, since thresholds are vendor- and disease-specific
Reject measurements with IQR/median above the quality threshold rather than reporting an unreliable stage
Exclude congestion, acute hepatitis and cholestasis before attributing high stiffness to fibrosis
Combine elastography with grey-scale, spleen size and Doppler for portal hypertension assessment (Baveno criteria)

Structured Report

State technique (2D SWE vs pSWE), vendor/system, probe and fasting status
Report median stiffness in kPa (and/or m/s), number of valid measurements and IQR/median quality ratio
Interpret against the appropriate aetiology-specific thresholds and give an estimated fibrosis category
Note confounders that may affect reliability
Give an impression and recommend correlation with serum markers or follow-up as indicated

References

SRU Consensus Conference Statement on Liver Elastography (Barr RG et al., Radiology 2020)
EFSUMB Guidelines and Recommendations on the Clinical Use of Liver Ultrasound Elastography
AASLD Practice Guidance on Noninvasive Assessment of Liver Fibrosis
Ferraioli G et al. Liver Ultrasound Elastography: WFUMB Guidelines

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

Liver Shear-Wave Elastography

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References