Spleen and Liver Stiffness in Portal Hypertension: WFUMB 2024
Clinical Focus of WFUMB 2024
The update to the WFUMB Guidelines/Guidance on Liver Multiparametric Ultrasound, 2024 highlights portal hypertension as a distinct application area for elastography. The main practical idea: liver stiffness reflects fibrosis and the sinusoidal component of resistance, while spleen stiffness is more closely related to portosystemic hemodynamics and hypersplenism. Therefore, LSM and SSM complement each other in compensated advanced chronic liver disease, cACLD.
Clinically significant portal hypertension, CSPH, is defined as HVPG ≥10 mmHg. In routine practice, HVPG is not always performed, so WFUMB 2024 supports the integration of elastography with Baveno VII criteria for rule-out and rule-in CSPH, as well as for selecting patients for endoscopy.
Where Baveno VII Thresholds Apply
Numerical thresholds primarily apply to the compensated course of chronic liver disease. They should not be mechanically applied in cases of decompensation, significant acute liver injury, cholestasis, congestive hepatopathy, infiltrative processes, or technically questionable measurement. Importantly, the most strictly validated thresholds are for transient elastography; for point shear wave elastography and 2D shear wave elastography, values depend on the manufacturer and protocol.
WFUMB emphasizes: the report should answer not only how many kPa, but also whether a specific clinical algorithm can be applied to this patient.
Main LSM and SSM Thresholds
| Task | Criterion | Interpretation | Key Limitation |
|---|---|---|---|
| Exclude cACLD | LSM by transient elastography <10 kPa | cACLD is unlikely in the absence of other clinical or imaging signs | Does not replace clinical assessment |
| Suspect cACLD | LSM 10–15 kPa | Value is compatible with cACLD and requires correlation with etiology and laboratory | Gray zones require dynamics and context |
| Highly probable cACLD | LSM >15 kPa | cACLD is highly probable | Increased LSM may not only be due to fibrosis |
| Rule-out CSPH | LSM ≤15 kPa and platelets ≥150×10^9/L | CSPH is unlikely | Baveno VII criterion for compensated disease |
| Rule-in CSPH | LSM ≥25 kPa | CSPH is probable in validated etiological groups of cACLD | Special caution in obesity and outside validated populations |
| Intermediate zone with high probability of CSPH | LSM 20–25 kPa and platelets <150×10^9/L or LSM 15–20 kPa and platelets <110×10^9/L | Probability of CSPH is not less than 60% | Clinical stratification needed, not a binary answer |
| SSM for rule-out CSPH | SSM <21 kPa | CSPH is unlikely in virus-associated cACLD | Threshold pertains to transient elastography |
| SSM for rule-in CSPH | SSM >50 kPa | CSPH is probable in virus-associated cACLD | Not a universal threshold for all SWE systems |
| Low probability of high-risk varices | SSM ≤40 kPa | May support the decision to defer endoscopy in selected patients | Apply together with LSM, platelets, and clinical scenario |
Liver Stiffness: What It Provides
LSM remains a basic non-invasive test for cACLD. A value <10 kPa helps exclude advanced chronic liver disease, 10–15 kPa forms a suspicion zone, and >15 kPa makes cACLD highly probable. For portal hypertension, the main practical division is different: ≤15 kPa with platelets ≥150×10^9/L versus ≥25 kPa.
With LSM ≥25 kPa, the probability of CSPH is sufficient for clinical rule-in in groups where the criterion is validated. With LSM below this level, risk cannot be automatically considered low: thrombocytopenia shifts the patient into an intermediate or high-probability category.
Why Measure the Spleen
SSM reflects changes in the portal system differently than LSM. As portal hypertension progresses, the spleen becomes stiffer due to venous congestion, tissue remodeling, and immuno-hematological changes. Therefore, SSM can be especially useful where LSM falls into a gray zone.
WFUMB 2024 emphasizes that the strongest evidence base for numerical SSM thresholds pertains to transient elastography. For virus-associated cACLD, SSM <21 kPa helps exclude CSPH, and SSM >50 kPa confirms it. This does not mean that 21 and 50 kPa can be transcribed into a report for any 2D-SWE system.
Varices and Endoscopy Decision
Baveno VII criteria as presented in WFUMB 2024 link LSM, platelets, and SSM with the risk of varices requiring attention. If the patient is not a candidate for non-selective beta-blockers, endoscopic screening is indicated at LSM ≥20 kPa or platelets ≤150×10^9/L. Conversely, low LSM combined with preserved platelet count supports a strategy of observation without immediate endoscopy.
SSM adds a second line of stratification: SSM ≤40 kPa indicates a low probability of high-risk varices. Practically, this is useful for patients who are near the decision boundary by LSM and platelets, but interpretation should be cautious and method-specific.
Methodology and Measurement Quality
The protocol should document the elastography method, device, probe, anatomical zone, measurement success, and reasons for limitations. For the liver, standardized measurement in the right lobe via intercostal access avoiding large vessels, the capsule, and focal changes is preferred. For the spleen, critical factors include the intercostal window, sufficient parenchyma volume, and absence of significant artifacts from ribs and breathing.
A report with only one number without specifying the method is clinically incomplete. The formulation SSM 42 kPa carries different weight depending on whether it was obtained by transient elastography or another SWE technology.
How to Write a Conclusion
The optimal conclusion for portal hypertension should include four blocks: LSM in kPa, SSM in kPa if a quality window is available, platelet count, and applicability of Baveno VII criteria. For example: LSM corresponds to rule-in CSPH by criterion ≥25 kPa or LSM ≤15 kPa with platelets ≥150×10^9/L corresponds to rule-out CSPH. If data fall into an intermediate zone, this should be explicitly stated.
Do not write cirrhosis excluded solely based on low stiffness or portal hypertension proven with technically unreliable SSM. It is more accurate to use probabilistic formulations: signs in favor of CSPH, CSPH unlikely by Baveno VII criteria, result outside the validated range of application.
Practical Algorithm
- Confirm that it is a case of compensated chronic liver disease and there are no obvious factors for false stiffness elevation.
- Perform LSM with a validated method and correlate with platelets.
- If LSM ≤15 kPa and platelets ≥150×10^9/L, indicate rule-out CSPH.
- If LSM ≥25 kPa, indicate rule-in CSPH with appropriate etiology and clinical context.
- In the gray zone, add SSM, especially in virus-associated cACLD.
- For variceal risk, consider LSM ≥20 kPa, platelets ≤150×10^9/L, and SSM ≤40 kPa as a sign of low probability of high-risk varices.
Main Pitfalls
The first pitfall is transferring transient elastography thresholds to 2D-SWE without validation. The second is ignoring platelets: LSM alone does not fully describe portal hypertension. The third is applying Baveno VII criteria to decompensated patients as a screening population. The fourth is a conclusion without clinical action: the physician must understand whether CSPH is excluded, confirmed, or requires further stratification.
WFUMB 2024 effectively translates elastography from a descriptive mode to an algorithmic one: LSM is responsible for entry into cACLD and primary CSPH assessment, SSM refines portal hemodynamics and variceal risk, and platelets link ultrasound data with clinical decision-making.
Frequently asked questions
Can SSM thresholds of 21, 40, and 50 kPa be used for 2D-SWE?
Not automatically. In WFUMB 2024, these thresholds are provided in the context of transient elastography; for pSWE and 2D-SWE, values depend on the system and require method-specific validation.
What is the most practical criterion for excluding CSPH?
LSM ≤15 kPa by transient elastography along with platelets ≥150×10^9/L. This result corresponds to rule-out CSPH according to Baveno VII in the applicable cACLD population.
When is SSM particularly useful?
In intermediate values of LSM and platelets, as well as in assessing the risk of high-risk varices. In virus-associated cACLD, SSM <21 kPa supports rule-out CSPH, >50 kPa supports rule-in CSPH, and ≤40 kPa indicates a low probability of high-risk varices.