SWE of Liver Transplant: Capabilities, Fibrosis Thresholds, and Method Limitations
The provided sources lack specific SWE thresholds for diagnosing liver transplant rejection and separately validated fibrosis cut-offs for it [clarify]. Below are general indicative liver fibrosis thresholds for point SWE (ElastPQ) and the method's technical limitations relevant to parenchyma examination.
Indicative Fibrosis Thresholds (EFSUMB, ElastPQ / point SWE data)
| Stage | Stiffness, kPa |
|---|---|
| F0–F1 | < 7.0 |
| F ≥ 2 | ≥ 7.0 |
| F ≥ 3 | ≥ 9.0–9.5 |
| F4 (cirrhosis) | ≥ 12.0–13.0 |
Exact thresholds vary by etiology: higher in alcoholic liver disease and cholestasis, lower in NAFLD. For 2D-SWE (SSI) according to EFSUMB (Update 2017), the cut-off for ≥ F2 is 7.1–8.0 kPa (Young's modulus), for F4 — 10.1–11.7 kPa.
Technical Guidelines for Performing SWE
According to EFSUMB (Course Book, 2018), liver stiffness measurement by SWE should be performed through the right intercostal space in the supine position, with the right arm abducted, during breath hold, avoiding deep inspiration before holding breath (LoE 2b, GoR B; strong consensus). The examination should be conducted by experienced operators (LoE 2b, GoR B; strong consensus).
Example protocol parameters (point SWE / ElastPQ): fasting ≥ 4 hours, intercostal access to the right lobe (segments V–VIII), depth of the area of interest 1–3 cm from the capsule without including the capsule, 10 measurements, reliability criterion IQR/Med ≤ 30%, the median is reported in the conclusion.
Limitations and Contraindications
SWE should not be performed in cases of acute hepatitis, transaminase flares (ALT > 5 ULN), extrahepatic cholestasis, and congestive heart failure (EFSUMB). These factors are particularly significant in transplant recipients, where inflammatory episodes, cholestasis, and congestion are common and may elevate stiffness values. The reason for unacceptable quality (obesity, ascites, cholestasis, heart failure, inflammatory episode) should be noted in the protocol.
There is no separate data on the specificity of SWE for differentiating fibrosis and acute rejection of liver transplants in the provided fragments [clarify].
Frequently asked questions
Are there validated SWE thresholds for liver transplant rejection?
There are no specific SWE thresholds for diagnosing liver transplant rejection in the provided sources [clarify].
What fibrosis thresholds should be used for point SWE (ElastPQ)?
According to EFSUMB: F0–F1 < 7.0 kPa; F ≥ 2 ≥ 7.0 kPa; F ≥ 3 ≥ 9.0–9.5 kPa; F4 ≥ 12.0–13.0 kPa. Thresholds vary by etiology.
Under what conditions should SWE not be performed?
In cases of acute hepatitis, transaminase flares (ALT > 5 ULN), extrahepatic cholestasis, and congestive heart failure (EFSUMB).
What is the reliability criterion for measurement?
IQR/Med ≤ 30%; the median of the measurements is reported in the conclusion (example protocol — 10 measurements).
How should the patient and probe be positioned correctly?
Supine position, right arm abducted, access through the right intercostal space, during breath hold without deep inspiration; area of interest 1–3 cm from the capsule without including it.