A review of the use of transient elastography in the assessment of fibrosis and steatosis in the post-liver transplant patient

The Effects of Sustained Immunosuppression Withdrawal After Liver Transplantation on Metabolic Syndrome

BACKGROUND

Liver transplant (LT) recipients often experience adverse effects of immunosuppressive (IS) drugs, especially on metabolic profiles. Selected LT recipients can achieve successful IS withdrawal; however, its effects on metabolic syndrome (MS) are unknown.

METHODS

This is a retrospective single-center study investigating the incidence and/or regression of MS in 75 selected LT recipients who were previously enrolled in prospective IS withdrawal trials between 1999 and 2017. Patients who were transplanted due to nonalcoholic steatohepatitis/metabolic-associated fatty liver disease were excluded, as well as those with a follow-up <3 y after IS weaning.

RESULTS

Forty-four patients (58.7%) achieved sustained withdrawal or minimization of immunosuppression (WMIS) and 31 patients (41.3%) required reintroduction of immunosuppression (no-WMIS). Among LT recipients who were metabolically healthy (n = 52, 69.3%) before the start of IS weaning, there was a significantly lower rate of de novo MS in WMIS patients compared with no-WMIS patients after 5 y (8.3% and 47.8%, respectively, P = 0.034). Of 23 LT recipients (30.7%) who had MS at the time of commencing IS withdrawal, complete regression of MS was observed in 47.1% of WMIS patients and in none (0%) of the no-WMIS patients after 5 y (P = 0.054). Furthermore, individual components of MS were better controlled in IS-weaned patients, such as arterial hypertension and abnormal serum lipids.

CONCLUSIONS

Achievement of sustained IS withdrawal reduces the incidence of de novo MS development in metabolically healthy patients and increases the likelihood of MS regression in patients with established MS. The foreseeable long-term beneficial effects of these favorable metabolic changes on morbidity and mortality of LT recipients require further investigation.

Clinical practice guidelines of the Catalan Society of Gastroenterology about hepatic elastography 2022

INTRODUCTION

After almost 20 years using transient elastography (TE) for the non-invasive diagnosis of liver fibrosis, its use has been extended to population screening, evaluation of steatosis and complications of cirrhosis. For this reason, the «Catalan Society of Gastroenterology» commissioned a group of experts to update the first document carried out in 2011.

MATERIAL AND METHODS

The working group (8 doctors and 4 nurses) prepared a panel of questions based on the online survey «Hepatic Elastography in Catalonia 2022» following the PICO structure and the Delphi method.

RESULTS

The answers are presented with the level of evidence, the degree of recommendation and the final consensus after being evaluated by two external reviewers.

CONCLUSION

Transient elastography uses the simplest and most reliable elastographic method to quantify liver fibrosis, assess steatosis, and determine the risk of complications in patients with cirrhosis. The document has been endorsed by the "Catalan Society of Gastroenterology" and the "Col·legi Oficial d'Infermeres i Infermers de Barcelona".

Fibrosis and steatosis of the liver graft: Are non-invasive tests useful? A short review

As life expectancy of liver transplanted patients improves, new questions are arising to avoid progressive graft loss. The spectrum of chronic inflammation and fibrosis are known to be important triggers in the alteration of graft function. Liver biopsy remains the gold standard to better understand progressive, normal, and abnormal histological modifications of the graft. In parallel, the interest for metabolic steatosis development in post-transplantation is also growing. Long-term survival of these patients involves the management of comorbidities including metabolic syndrome and cardiovascular diseases. Early detection of altered graft parenchyma, and monitoring of its evolution are undoubtedly essential. Non-invasive methods including transient elastography and fibrosis biomarkers are attractive tools to avoid drawbacks and complications of liver biopsy. Accuracy of these methods are well-known in a pre-transplantation setting, but evidence is lacking in post-transplantation setting. We review current knowledge of progressive liver fibrosis and steatosis development after transplantation and non-invasive methods of their assessment.

Non-Invasive Measurement of Hepatic Fibrosis by Transient Elastography: A Narrative Review

Transient elastography by FibroScan® (Echosens, Paris, France) is a non-invasive method that can provide a reliable measurement of liver fibrosis through the evaluation of liver stiffness. Despite its limitations and risks, liver biopsy has thus far been the only procedure able to provide data to quantify fibrosis. Scientific evidence and clinical practice have made it possible to use FibroScan® in the diagnostic work-up of several liver diseases to monitor patients' long-term treatment response and for complication prevention. For these reasons, this procedure is widely used in clinical practice and is still being investigated for further applications. The aim of this narrative review is to provide a comprehensive overview of the main applications of transient elastography in the current clinical practice.

A deep learning framework for personalised dynamic diagnosis of graft fibrosis after liver transplantation: a retrospective, single Canadian centre, longitudinal study

BACKGROUND

Recurrent graft fibrosis after liver transplantation can threaten both graft and patient survival. Therefore, early detection of fibrosis is essential to avoid disease progression and the need for retransplantation. Non-invasive blood-based biomarkers of fibrosis are limited by moderate accuracy and high cost. We aimed to evaluate the accuracy of machine learning algorithms in detecting graft fibrosis using longitudinal clinical and laboratory data.

METHODS

In this retrospective, longitudinal study, we trained machine learning algorithms, including our novel weighted long short-term memory (LSTM) model, to predict the risk of significant fibrosis using follow-up data from 1893 adults who had a liver transplantation between Feb 1, 1987, and Dec 30, 2019, with at least one liver biopsy post transplantation. Liver biopsy samples with indefinitive fibrosis stage and those from patients with multiple transplantations were excluded. Longitudinal clinical variables were collected from transplantation to the date of last available liver biopsy. Deep learning models were trained on 70% of the patients as the training set and 30% of the patients as the test set. The algorithms were also separately tested on longitudinal data from patients in a subgroup of patients (n=149) who had transient elastography within 1 year before or after the date of liver biopsy. Weighted LSTM model performance for diagnosing significant fibrosis was compared against LSTM, other deep learning models (recurrent neural network and temporal convolutional network), and machine learning models (Random Forest, Support vector machines, Logistic regression, Lasso regression, and Ridge regression) and aspartate aminotransferase-to-platelet ratio index (APRI), fibrosis-4 index (FIB-4), and transient elastography.

FINDINGS

1893 people who had a liver transplantation (1261 [67%] men and 632 [33%] women) with at least one liver biopsy between Jan 1, 1992, and June 30, 2020, were included in the study (591 [31%] cases and 1302 [69%] controls). The median age at liver transplantation was 53·7 years (IQR 47·3-59·0) for cases and 55·3 years (48·0 to 61·2) for controls. The median time interval between transplant and liver biopsy was 21 months (5 to 71). The weighted LSTM model (area under the curve 0·798 [95% CI 0·790 to 0·810]) consistently outperformed other methods, including unweighted LSTM (0·761 [0·750 to 0·769]; p=0·031) Recurrent Neural Network (0·736 [0·721 to 0·744]), Temporal Convolutional Networks (0·700 [0·662 to 0·747], and Random Forest 0·679 [0·652 to 0·707]), FIB-4 (0·650 [0·636 to 0·663]) and APRI (0·682 [0·671 to 0·694]) when diagnosing F2 or worse stage fibrosis. In a subgroup of patients with transient elastography results, weighted LSTM was not significantly better at detecting fibrosis (≥F2; 0·705 [0·687 to 0·724]) than transient elastography (0·685 [0·662 to 0·704]). The top ten variables predictive for significant fibrosis were recipient age, primary indication for transplantation, donor age, and longitudinal data for creatinine, alanine aminotransferase, aspartate aminotransferase, total bilirubin, platelets, white blood cell count, and weight.

INTERPRETATION

Deep learning algorithms, particularly weighted LSTM, outperform other routinely used non-invasive modalities and could help with the earlier diagnosis of graft fibrosis using longitudinal clinical and laboratory variables. The list of most important predictive variables for the development of fibrosis will enable clinicians to modify their management accordingly to prevent onset of graft cirrhosis.

FUNDING

Canadian Institute of Health Research, American Society of Transplantation, Toronto General and Western Hospital Foundation, and Paladin Labs.

Liver transplantation immunology: Immunosuppression, rejection, and immunomodulation

Outcomes after liver transplantation have continuously improved over the past decades, but long-term survival rates are still lower than in the general population. The liver has distinct immunological functions linked to its unique anatomical configuration and to its harbouring of a large number of cells with fundamental immunological roles. The transplanted liver can modulate the immunological system of the recipient to promote tolerance, thus offering the potential for less aggressive immunosuppression. The selection and adjustment of immunosuppressive drugs should be individualised to optimally control alloreactivity while mitigating toxicities. Routine laboratory tests are not accurate enough to make a confident diagnosis of allograft rejection. Although several promising biomarkers are being investigated, none of them is sufficiently validated for routine use; hence, liver biopsy remains necessary to guide clinical decisions. Recently, there has been an exponential increase in the use of immune checkpoint inhibitors due to the unquestionable oncological benefits they provide for many patients with advanced-stage tumours. It is expected that their use will also increase in liver transplant recipients and that this might affect the incidence of allograft rejection. Currently, the evidence regarding the efficacy and safety of immune checkpoint inhibitors in liver transplant recipients is limited and cases of severe allograft rejection have been reported. In this review, we discuss the clinical relevance of alloimmune disease, the role of minimisation/withdrawal of immunosuppression, and provide practical guidance for using checkpoint inhibitors in liver transplant recipients.

Metabolic syndrome, hepatic fibrosis, and steatosis diagnosed by liver stiffness measurement and controlled attenuation parameter after liver transplantation: the impact on long-term survival

BACKGROUND

Liver stiffness measurement (LSM) and controlled attenuation parameter (CAP) are used for diagnosis of liver fibrosis and steatosis. This study aimed to noninvasively evaluate hepatic steatosis and fibrosis in liver transplant recipients using CAP and LSM and the impact on survival of patients.

METHODS

In a prospective study, adult liver transplant recipients were included. CAP and LSM obtained during transient elastography (TE) were used for assessment of hepatic steatosis and fibrosis. Patients were followed during 4 years for mortality as the main outcome after liver transplantation.

RESULTS

From 296 patients, 24.7% and 25% of liver transplant recipients had liver steatosis and fibrosis in CAP and LSM, respectively. In multivariable Cox regression analysis, etiology of liver disease (NASH versus non-NASH) (HR: 3.125; 95% CI: 1.594-6.134; p = 0.001), and post-transplant diabetes mellitus (PTDM) (HR: 2.617; 95% CI: 1.396-4.926; p = 0.003) were associated with hepatic steatosis after liver transplantation.  In multivariable Cox regression analysis, liver fibrosis was an independent predictor of mortality after liver transplantation (HR: 4.926; 95%CI: 1.779-13.513; p = 0.002).

CONCLUSION

CAP and LS measurement during TE are useful methods for diagnosis of hepatic steatosis and fibrosis in liver transplant recipients. LS measurement might predict long-term survival of patients.

Minimal Development of Liver Fibrosis in Adult Tolerant Liver Transplant Recipients Late After Immunosuppressive Drug Weaning and Transplantation

BACKGROUND

Operationally tolerant liver transplant (LTx)-recipients can be weaned off immunosuppressive (IS) drugs without development of graft rejection. However, it is feared that liver fibrosis might develop after complete IS weaning. The purpose of this small single-center study was to assess liver fibrosis in adult tolerant LTx recipients long after LTx and IS weaning.

METHODS

Liver fibrosis was assessed in adult tolerant LTx-recipients (n = 9) using noninvasive transient elastography and measurements of multiple pro- and antifibrotic serum markers associated with liver fibrosis. The data was collected for 2 subsequent years; 8 and 9 years after IS weaning and 19 and 20 years after transplantation. Healthy individuals (n = 9) matched for age and sex were included as a reference for fibrosis-related serum markers. This study was conducted in accordance with the Declaration of Helsinki and approved by the medical ethics committee of our institution.

RESULTS

Transient elastography indicated that 7 of 9 tolerant LTx recipients had no or minimal liver fibrosis (F0-F1), whereas 2 recipients had moderate or severe liver fibrosis (F2-F3). Most fibrosis-related serum markers in tolerant LTx recipients were within or close to the range obtained for healthy individuals.

CONCLUSIONS

The results from this small, single-center study indicated that most adult tolerant LTx recipients have no or minimal liver graft fibrosis long after transplantation and IS weaning, and their fibrosis-related serum marker profile indicates an absence of a profibrotic status.

The use of transient elastography in identifying sub-clinical chronic ductopenic rejection in adult liver transplant recipients: A case series

BACKGROUND

Transient elastography has become a standard tool for the accurate non-invasive assessment of liver stiffness and fat content. Liver transplant recipients can develop allograft fibrosis during long-term follow-up despite normal or mildly abnormal liver chemistries. Tapering of immunosuppression in long-term liver transplant survivors is performed relying solely on liver chemistries. It is important to know if underlying liver histology would be abnormal or if rejection was present as this would alter the desire to decrease stable maintenance doses of immunosuppression.

METHODS

We present our experience of five liver transplant recipients who had transient elastography performed prior to consideration of weaning of their immunosuppression.

RESULTS

All five patients showed signs of elevated liver stiffness on transient elastography in the setting of normal to slightly abnormal liver tests with very stable immunosuppressant doses. This prompted the performance of liver biopsies which demonstrated immune-mediated liver injury and thus negated the immunosuppression withdrawal.

CONCLUSION

Transient elastography has utility as a non-invasive method to evaluate allograft health in long-term liver transplant survivors and can be useful in the decision-making process for immunosuppression weaning.

A Diagnostic Test Meta-Analysis Evaluating Imaging-Based and Blood Biomarker-Based Assessment Tools for Fibrosis After Liver Transplantation

Early detection of liver graft fibrosis is crucial for risk stratification to identify patients for liver biopsy and timely treatment. However, diagnostic accuracy of noninvasive tests (NITs) remains unclear. Thus, this study sought to evaluate diagnostic accuracy of NITs in assessing liver allograft fibrosis and compare the differences in specificities and sensitivities among NITs. Medline and Embase databases were searched to include articles on diagnostic tests in liver transplantation (LT) patients with fibrosis. A meta-analysis on diagnostic test accuracy was conducted in a random-effects model. Sensitivities and specificities among the diagnostic tests were compared, and threshold values were calculated where applicable. A total of 25 articles were included. Vibration-controlled transient elastography (VCTE) met the minimum diagnostic accuracy requirements, yielding sensitivity, specificity, and diagnostic odds ratios of 0.9 (CI, 0.8-1.0), 0.9 (CI, 0.8-1.0), and 379.6 (CI, 45.8-1728.7), respectively. In the threshold assessment, the optimal cutoff was 9.30 kPa with a sensitivity, specificity, and area under the curve of 0.7 (CI, 0.5-0.9), 0.9 (CI, 0.8-0.9), and 0.9 (CI, 0.8-0.9), respectively. For significant fibrosis, acoustic radiation force impulse (ARFI) was superior to FibroTest (LabCorp [Burlington, NC]) and magnetic resonance elastography (MRE) in sensitivity. VCTE was superior to FibroTest in specificity. For advanced fibrosis, ARFI was superior to the Fibrosis-4 Index (FIB-4) in sensitivity. VCTE was superior to the AST to Platelet Ratio Index (APRI), MRE, and FIB-4 in specificity. In cirrhosis, VCTE was superior to APRI in specificity (P = 0.004) with comparable sensitivity. This study demonstrates the potential of VCTE and ARFI as diagnostic tools for fibrosis in LT recipients compared with blood-based NITs, which were shown to be less optimal.

Utility of Metabolomic Biomarkers to Identify Nonalcoholic Fatty Liver Disease in Liver Transplant Recipients

Nonalcoholic fatty liver disease (NAFLD) is a rising indication for liver transplantation (LT). Identification of NAFLD recurrence and those at risk for more progressive disease after LT remains elusive as the diagnosis requires biopsy, which is invasive and impractical for serial monitoring. We therefore aimed to identify metabolites in the blood associated with recurrent NAFLD that could potentially be used for detection and monitoring.

Antibody-mediated rejection of the liver allograft: An update and a clinico-pathological perspective

Antibody-mediated rejection after liver transplantation is an under-recognised cause of allograft injury. While definitions of acute and chronic antibody-mediated rejection have increased clinical awareness, timely identification and management of antibody-mediated rejection remain difficult because of complexities in diagnosis and histopathology, lack of treatment protocols, and unclear long-term outcomes. While recent cohort studies assessing the importance of donor-specific antibodies have aided in its diagnosis, literature on the treatment of antibody-mediated rejection in liver transplantation remain limited to case reports and small series. Further increasing the awareness and timely recognition of antibody-mediated rejection post-liver transplantation is crucial in order to stimulate future research and the development of protocols for its diagnosis and treatment. This review will summarise recent advances in the clinical diagnosis and treatment of antibody-mediated rejection in liver transplantation, as well as some of the histopathologic features (on liver biopsy tissue) of acute and chronic antibody-mediated rejection.

Noninvasive markers of liver steatosis and fibrosis after liver transplantation - Where do we stand?

In the last two decades, advances in immunosuppressive regimens have led to fewer complications of acute rejection crisis and consequently improved short-term graft and patient survival. In parallel with this great success, long-term post-transplantation complications have become a focus of interest of doctors engaged in transplant medicine. Metabolic syndrome (MetS) and its individual components, namely, obesity, dyslipidemia, diabetes, and hypertension, often develop in the post-transplant setting and are associated with immuno-suppressive therapy. Nonalcoholic fatty liver disease (NAFLD) is closely related to MetS and its individual components and is the liver manifestation of MetS. Therefore, it is not surprising that MetS and its individual components are associated with recurrent or "de novo" NAFLD after liver transplantation (LT). Fibrosis of the graft is one of the main determinants of overall morbidity and mortality in the post-LT period. In the assessment of post-LT steatosis and fibrosis, we have biochemical markers, imaging methods and liver biopsy. Because of the significant economic burden of post-LT steatosis and fibrosis and its potential consequences, there is an unmet need for noninvasive methods that are efficient and cost-effective. Biochemical scores can overestimate fibrosis and are not a good method for fibrosis evaluation in liver transplant recipients due to frequent post-LT thrombocytopenia. Transient elastography with controlled attenuation parameter is a promising noninvasive method for steatosis and fibrosis. In this review, we will specifically focus on the evaluation of steatosis and fibrosis in the post-LT setting in the context of de novo or recurrent NAFLD.

Assessment of Steatosis and Fibrosis in Liver Transplant Recipients Using Controlled Attenuation Parameter and Liver Stiffness Measurements

AIM

The primary objective of this study was to evaluate the prevalence of increased controlled attenuation parameter (CAP) and liver stiffness measurements (LSM) as surrogate markers of liver steatosis and fibrosis in liver transplant recipient (LTR). Secondary objectives were to determine the predictors of increased CAP and LSM in population of LTR.

METHODS

In this prospective, cross-sectional study, we have evaluated 175 LTRs' mean age as 61 (53-65) with a functioning graft for more than one year who came for regular outpatient examinations to the Department of Gastroenterology, University Hospital (UH) Merkur, Zagreb, Croatia.

RESULTS

Of 175 analyzed LTRs, 34.28% had obesity, 64.00% had hypertension, 38.28% had diabetes, and 58.85% had hyperlipidemia. The prevalence of liver steatosis was 68.57%, while the prevalence of severe liver steatosis was 46.85%. On multivariate analysis, independent factors associated with liver steatosis were male gender, total cholesterol as positive predictor, and HDL as negative predictor, and independent factors positively associated with severe liver steatosis were higher body mass index (BMI) and higher triglyceride levels. The prevalence of moderate liver fibrosis was 54.85%, while the prevalence of advanced liver fibrosis was 24%. On multivariate analysis, independent factors positively associated with moderate fibrosis were gamma-glutamyl transferase (GGT) and CAP, while the independent factor positively associated with advanced fibrosis was GGT.

CONCLUSION

Our study showed high prevalence of increased CAP and LSM measurements as surrogate markers of liver steatosis and fibrosis. Metabolic syndrome components were highly present and were associated with CAP and LSM values as well as in the pretransplant setting. Due to high prevalence of metabolic comorbidities and nonalcoholic fatty liver disease in LTRs and the lack of the abnormal liver test in a significant number of these patients, TE with CAP may be a reasonable initial assessment for LTRs with one or more components of the metabolic syndrome.

Current Challenges in the Post-Transplant Care of Liver Transplant Recipients in Germany

Improving long-term patient and graft survival after liver transplantation (LT) remains a major challenge. Compared to the early phase after LT, long-term morbidity and mortality of the recipients not only depends on complications immediately related to the graft function, infections, or rejection, but also on medical factors such as de novo malignancies, metabolic disorders (e.g., new-onset diabetes, osteoporosis), psychiatric conditions (e.g., anxiety, depression), renal failure, and cardiovascular diseases. While a comprehensive post-transplant care at the LT center and the connected regional networks may improve outcome, there is currently no generally accepted standard to the post-transplant management of LT recipients in Germany. We therefore described the structure and standards of post-LT care by conducting a survey at 12 German LT centers including transplant hepatologists and surgeons. Aftercare structures and form of cost reimbursement considerably varied between LT centers across Germany. Further discussions and studies are required to define optimal structure and content of post-LT care systems, aiming at improving the long-term outcomes of LT recipients.