Liver Ultrasound Elastography: Fibrosis, cACLD, and Portal Hypertension (WFUMB 2024)
What the WFUMB 2024 Update Changed
WFUMB 2024 updates the 2018 guidelines on liver elastography and integrates liver stiffness measurement into multiparametric ultrasound. The practical focus is not only on the stage of fibrosis on a biopsy scale but on identifying compensated advanced chronic liver disease, cACLD, and the risk of clinically significant portal hypertension, CSPH.
This is important in MAFLD: steatosis, inflammation, obesity, and metabolic factors increase the prevalence of intermediate stiffness values. Therefore, the conclusion should answer the clinical question: is cACLD excluded, is monitoring required as in cACLD, are there signs of CSPH risk.
Terms for Protocol
- LSM — liver stiffness measurement.
- VCTE/TE — vibration-controlled transient elastography; many prognostic thresholds are validated for it.
- pSWE and 2D-SWE — ultrasound shear wave methods integrated into the ultrasound scanner; thresholds depend on the platform and should be interpreted considering the methodology.
- cACLD — compensated advanced chronic liver disease, the clinical equivalent of significant fibrosis/early cirrhosis.
- CSPH — clinically significant portal hypertension, a key predictor of variceal bleeding and decompensation.
Key VCTE/TE Thresholds by WFUMB 2024
| Indicator | Threshold | Clinical Interpretation |
|---|---|---|
| LSM | <10 kPa | cACLD is excluded in the absence of other clinical or imaging signs of chronic progressive liver damage |
| LSM | 10–15 kPa | cACLD is likely; clinical-laboratory correlation and dynamic monitoring are needed |
| LSM | >15 kPa | cACLD is highly likely |
| LSM + platelets | ≤15 kPa and ≥150×10^9/L | CSPH is unlikely; the combination is used to exclude clinically significant portal hypertension |
| LSM | ≥25 kPa | CSPH is likely/confirmed in validated groups of chronic liver diseases |
| LSM + platelets | 20–25 kPa and <150×10^9/L | High likelihood of CSPH; requires management as a high-risk group |
| LSM + platelets | 15–20 kPa and <110×10^9/L | High likelihood of CSPH; requires clinical routing |
Why Not Just Write 'F2' or 'F4'
WFUMB emphasizes the limitation of universal cut-offs for histological staging. Liver stiffness depends not only on collagen: it is influenced by active inflammation, cholestasis, venous congestion, food intake, significant steatosis, and technical factors. Therefore, the same LSM value can have different prognostic value in viral hepatitis, alcohol-associated damage, and MAFLD.
A practical formulation is better built around the probability of cACLD and CSPH. If it is necessary to indicate the stage of fibrosis, it should be designated as probabilistic: 'elastographic signs of significant fibrosis/cACLD' or 'no data for cACLD by LSM', rather than as an absolute histological diagnosis.
Algorithm for LSM Interpretation
- Check the clinical context: etiology of liver disease, biochemical activity, cholestasis, signs of right ventricular failure, previous imaging data.
- Ensure the study is technically acceptable for the specific device and methodology.
- First, answer the cACLD question: <10 kPa, 10–15 kPa, or >15 kPa.
- If cACLD is likely or already known, assess the risk of CSPH: compare LSM with platelet count.
- For LSM ≥25 kPa or unfavorable combinations of LSM and platelets, indicate a high risk of CSPH and the need for clinical routing.
Portal Hypertension: How to Link Ultrasound, LSM, and Platelets
Liver stiffness is not a direct measurement of portal vein pressure but a validated non-invasive marker of risk. According to WFUMB 2024, the combination of LSM ≤15 kPa and platelets ≥150×10^9/L allows excluding CSPH in patients with cACLD. At the opposite end, LSM ≥25 kPa indicates a high likelihood of CSPH in groups where the criterion is validated.
The gray zone requires particularly careful conclusions. Values of 20–25 kPa with platelets <150×10^9/L and 15–20 kPa with platelets <110×10^9/L are associated with combinations of high CSPH likelihood. It is useful to separately indicate the absence or presence of splenomegaly, ascites, collaterals, and portal vein thrombosis in the protocol, but these signs do not replace LSM interpretation.
MAFLD: Features of Threshold Application
In MAFLD, elastography is especially in demand due to the large number of patients with asymptomatic fibrosis. However, obesity, steatosis, and metabolic inflammation increase the risk of technical limitations and intermediate results. Therefore, WFUMB 2024 supports a combined approach: LSM is interpreted together with laboratory data, platelets, and the clinical likelihood of progressive disease.
The conclusion should not overstate the stage based solely on a single elevated LSM. If the result is in the range of 10–15 kPa, it is more accurate to indicate the likelihood of cACLD and recommend correlation with clinical-laboratory data or follow-up with the same methodology.
What Should Be in the Ultrasound Elastography Conclusion
- Methodology: VCTE/TE, pSWE, or 2D-SWE; manufacturer/probe if necessary.
- Median LSM value in kPa, if available — also shear wave speed.
- Technical suitability of the measurement according to the criteria of the system used.
- Interpretation by clinical categories: cACLD excluded, likely, or highly likely.
- Assessment of CSPH risk if platelet data is available.
- Ultrasound signs of complications: ascites, splenomegaly, portosystemic collaterals, focal lesions.
Example Formulation
LSM 8.4 kPa: 'According to VCTE elastography, liver stiffness is below the 10 kPa threshold; in the absence of other clinical/imaging signs, no data for cACLD is obtained.'
LSM 13.2 kPa: 'Liver stiffness is in the range of 10–15 kPa; cACLD is likely, correlation with clinical-laboratory data and dynamic monitoring is required.'
LSM 28 kPa: 'Liver stiffness ≥25 kPa; with the corresponding etiology of chronic liver disease, data corresponds to a high risk of CSPH.'
Frequently asked questions
Can a single LSM determine the exact stage F2 or F4?
No. WFUMB 2024 emphasizes probabilistic interpretation: thresholds depend on etiology, method, and clinical context. It is more practical to indicate the likelihood of cACLD and CSPH in the protocol.
What is the main threshold for excluding cACLD?
For VCTE/TE, an LSM value <10 kPa in the absence of other clinical or imaging signs allows excluding cACLD.
When should clinically significant portal hypertension be considered in elastography?
LSM ≥25 kPa indicates a high likelihood of CSPH in validated groups. CSPH is unlikely with a combination of LSM ≤15 kPa and platelets ≥150×10^9/L.