HRCT Features of Acute Rejection in Patients With Bilateral Lung Transplantation: The Usefulness of Lesion Distribution

Real-time and non-invasive acute lung rejection diagnosis using confocal LASER Endomicroscopy in lung transplant recipients: Results from the CELTICS study

BACKGROUND AND OBJECTIVE

Traditionally, the diagnosis of acute rejection (AR) relies on invasive transbronchial biopsies (TBBs) to obtain histopathological samples. We aimed to evaluate the diagnostic yield of probe-based confocal laser endomicroscopy (pCLE) as a complementary and non-invasive tool for ACR screening, comparing its results with those obtained from TBBs.

METHODS

Between January 2015 and April 2022, we conducted a retrospective study of all lung transplant recipients aged over 18 years at Toulouse University Hospital (France). All patients who underwent bronchoscopies with both TBBs and pCLE imaging were included. Two experienced interpreters (TV and MS) reviewed the pCLE images independently, blinded to all clinical information and pathology results.

RESULTS

From 120 procedures in 85 patients, 34 abnormal histological samples were identified. Probe-based confocal laser endomicroscopy revealed significant associations between both alveolar (ALC) and perivascular (PVC) cellularities and abnormal histological samples (p<0.0001 and 0.003 respectively). Alveolar cellularity demonstrated a sensitivity (Se) of 85.3 %, specificity (Spe) of 43 %, positive predictive value (PPV) of 37.2 % and negative predictive value (NPV) of 88.1 %. For PVC, Se was 70.6 %, Spe 80.2 %, PPV 58.5 % and NPV 87.3 %. Intra-interpreter correlation (TV) was 88.3 % for the number of vessels (+/-1), 98.3 % for ALC and 90 % for PVC. Inter-interpreter correlation (TV and MS) was 80 % for vessels (+/-1), 97.5 % for ALC and 83.3 % for PVC.

CONCLUSION

Our study demonstrates the feasibility of incorporating pCLE into clinical practice, demonstrating good diagnostic yield and reproducible outcomes in the screening of AR in lung transplant recipients.

Circulating donor-derived cell-free DNA as a marker for rejection after lung transplantation

Objective

Recently, circulating donor-derive cell free DNA (dd-cfDNA) has gained growing attention in the field of solid organ transplantation. The aim of the study was to analyze circulating dd-cfDNA levels in graft rejection, ACR and AMR separately for each rejection type compared with non-rejection, and assessed the diagnostic potential of dd-cfDNA levels in predicting graft rejection after lung transplantation.

Methods

A systematic search for relevant articles was conducted on Medline, Web of Science, China National Knowledge Infrastructure (CNKI), and Wanfang databases without restriction of languages. The search date ended on June 1, 2023. STATA software was used to analyze the difference between graft rejection, ACR, AMR and stable controls, and evaluate the diagnostic performance of circulating dd-cfDNA in detecting graft rejection.

Results

The results indicated that circulating dd-cfDNA levels in graft rejection, ACR, and AMR were significantly higher than non-rejection (graft rejection: SMD=1.78, 95% CI: 1.31-2.25, I2 = 88.6%, P< 0.001; ACR: SMD=1.03, 95% CI: 0.47-1.59, I2 = 89.0%, P < 0.001; AMR: SMD= 1.78, 95% CI: 1.20-2.35, I2 = 89.8%, P < 0.001). Circulating dd-cfDNA levels distinguished graft rejection from non-rejection with a pooled sensitivity of 0.87 (95% CI: 0.80-0.92) and a pooled specificity of 0.82 (95% CI: 0.76-0.86). The corresponding SROC yield an AUROC of 0.90 (95% CI: 0.87-0.93).

Conclusion

Circulating dd-cfDNA could be used as a non-invasive biomarker to distinguish the patients with graft rejection from normal stable controls.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023440467.

Thoracic Ultrasound in Lung Transplantation—Insights in the Field

The use of thoracic ultrasound (TUS) is a novel and dynamic diagnostic and monitoring modality that has shown remarkable advances within the last decade, with several published papers investigating its role within the field of lung transplantation. The aim of this current opinion review is to review the existing literature on the role of TUS in all stages of LTx, from in-donor lung evaluation to graft assessment on ex vivo lung perfusion and in the short- and long-term follow-up after LTx.

Application of plasma donor-derived cell free DNA for lung allograft rejection diagnosis in lung transplant recipients

BACKGROUND

Donor-derived cell-free DNA (dd-cfDNA) has been applied to monitor acute rejection (AR) in kidney and heart transplantation. This study was aimed to investigate the application of dd-cfDNA levels in the diagnosis of AR and chronic lung allograft dysfunction (CLAD) among the lung transplantation recipients (LTRs).

METHODS

One hundred and seventy LTRs were enrolled at the First Affiliated Hospital of Guangzhou Medical University between 1 June 2015 and 30 March 2021. Patients were divided into 4 groups: stable group, AR group, infection group and CLAD group. The level of dd-cfDNA was analyzed using target region sequencing and the performance characteristics of dd-cfDNA for diagnosis of AR and CLAD were determined, respectively.

RESULTS

Kruskal-Wallis test showed that there were some significant differences in the level of dd-cfDNA (%) among the 4 groups, with p < 0.001. Among them, the level of dd-cfDNA (%) was highest (median 2.17, IQR [1.40-3.82]) in AR group, and higher in CLAD group (median 1.07, IQR [0.98-1.31]), but lower in infection group (median 0.71, IQR [0.57-1.07]) and lowest in stable group (median 0.71, IQR [0.61-0.84]). AUC-ROC curve analysis showed that the threshold of dd-cfDNA for AR was 1.17%, with sensitivity being 89.19% and specificity being 86.47%, and the optimal threshold of 0.89% was determined of CLAD, with sensitivity being 95.00% and specificity of 76.99%.

CONCLUSIONS

Plasma dd-cfDNA could be a useful tool for the assessment of lung allograft rejection, including AR and CLAD, and holds promise as a noninvasive biomarker for "allograft injury" in both acute and chronic rejection following lung transplantation.

Lung Allograft Rejection

Rejection is a major complication following lung transplantation. Acute cellular rejection (ACR), and antibody-mediated rejection (AMR) are risk factors for the subsequent development of chronic lung allograft dysfunction and worse outcomes after transplantation. Although ACR has well-defined histopathologic diagnostic criteria and grading, the diagnosis of AMR requires a multidisciplinary diagnostic approach. This article reviews the identification, clinical and pathologic features of, and therapeutic options for ACR and AMR.

Acute rejection and post lung transplant surveillance

Purpose

The purpose of this review is to summarize the current evidence on the evaluation and treatment of acute rejection after lung transplantation.

Results

Despite significant progress in the field of transplant immunology, acute rejection remains a frequent complication after transplantation. Almost 30% of lung transplant recipients experience at least one episode of acute cellular rejection (ACR) during the first year after transplant. Acute cellular rejection, lymphocytic bronchiolitis, and antibody-mediated rejection (AMR) are all risk factors for the subsequent development of chronic lung allograft dysfunction (CLAD). Acute cellular rejection and lymphocytic bronchiolitis have well-defined histopathologic diagnostic criteria and grading. The diagnosis of antibody-mediated rejection after lung transplantation requires a multidisciplinary approach. Antibody-mediated rejection may cause acute allograft failure.

Conclusions

Acute rejection is a risk factor for development of chronic rejection. Further investigations are required to better define risk factors, surveillance strategies, and optimal management strategies for acute allograft rejection.

Imaging Findings for Identifying and Evaluating Complications after Lung Transplantation in Patients with Advanced COVID-19: Two Case Reports

BACKGROUND

Lung transplantation might be a viable alternative for patients with irreversible lung injury secondary to coronavirus disease 2019 (COVID-19). Here, we describe two patients with end-stage COVID-19 that received lung transplantations, the clinical-radiologic manifestations of post-operative complications, and the imaging features of allograft rejection. <p> Case presentation: Case 1, a 66-year-old woman presented severe hypoxia after lung transplantation. Chest imaging revealed diffuse homogeneous infiltration in the donor lung. Dramatic resolution of the imaging abnormalities after intravenous administration of methylprednisolone favored a diagnosis of hyperacute rejection. The second is a 70-year-old man, who was infected with bacterial postoperatively. During the empiric antibiotic therapy, chest CT showed newly developed ground glass opacities with septal thickening, suggesting a diagnosis of acute rejection. High-dose corticosteroids therapy was initiated, and the patient recovered gradually. <p> Conclusion: This is the first report describing post-operative complications of lung transplantation in patients with advanced COVID-19. We presumed that imaging procedures could be a useful tool in early detecting lung transplant complications and selecting specific interventions for patients with COVID-19.

Acute Rejection in the Modern Lung Transplant Era

Acute cellular rejection (ACR) remains a common complication after lung transplantation. Mortality directly related to ACR is low and most patients respond to first-line immunosuppressive treatment. However, a subset of patients may develop refractory or recurrent ACR leading to an accelerated lung function decline and ultimately chronic lung allograft dysfunction. Infectious complications associated with the intensification of immunosuppression can also negatively impact long-term survival. In this review, we summarize the most recent evidence on the mechanisms, risk factors, diagnosis, treatment, and prognosis of ACR. We specifically focus on novel, promising biomarkers which are under investigation for their potential to improve the diagnostic performance of transbronchial biopsies. Finally, for each topic, we highlight current gaps in knowledge and areas for future research.

Imaging Evaluation of Airway Complications After Lung Transplant

Airway complications (ACs) after lung transplant remain a challenge and include bronchial dehiscence, bronchial stenosis, tracheobronchomalacia, infections, and bronchial fistulas. The spectrum of complications may coexist along a continuum and can be classified as early (<1 month after transplant) or late (>1 month), and anastomotic or nonanastomotic. Bronchiolitis obliterans is the most common form of chronic lung allograft rejection. Airway compromise is seen in rare instances of lung torsion, and imaging may provide helpful diagnostic clues. Computed tomography (CT) and bronchoscopy play major roles in the diagnosis and treatment of ACs after lung transplant. Chest CT with advanced postprocessing techniques is a valuable tool in evaluating for airways complications, for initial bronchoscopic treatment planning and subsequent posttreatment assessment. Various bronchoscopic treatment options may be explored to maintain airway patency. The goal of this article is to review imaging findings of ACs after lung transplantation, with emphasis on chest CT and bronchoscopic correlation.

Surveillance for acute cellular rejection after lung transplantation

Acute cellular rejection (ACR) is a common complication following lung transplantation (LTx), affecting almost a third of recipients in the first year. Established, comprehensive diagnostic criteria exist but they necessitate allograft biopsies which in turn increases clinical risk and can pose certain logistical and economic problems in service delivery. Undermining these challenges further, are known problems with inter-observer interpretation of biopsies and uncertainty as to the long-term implications of milder or indeed asymptomatic episodes. Increased risk of chronic lung allograft dysfunction (CLAD) has long been considered the most significant consequence of ACR. Consensus is lacking as to whether this applies to mild ACR, with contradictory evidence available. Given these issues, research into alternative, minimal or non-invasive biomarkers represents the main focus of research in ACR. A number of potential markers have been proposed, but none to date have demonstrated adequate sensitivity and specificity to allow translation from bench to bedside.

Imaging indications and findings in evaluation of lung transplant graft dysfunction and rejection

Lung transplantation is a treatment option in end-stage lung disease. Complications can develop along a continuum in the immediate or longer post-transplant period, including surgical and technical complications, primary graft dysfunction, rejection, infections, post-transplant lymphoproliferative disorder, and recurrence of the primary disease. These complications have overlapping clinical and imaging features and often co-exist. Time of onset after transplant is helpful in narrowing the differential diagnosis. In the early post transplantation period, imaging findings are non-specific and need to be interpreted in the context of the clinical picture and other investigations. In contrast, imaging plays a key role in diagnosing and monitoring patients with chronic lung allograft dysfunction. The goal of this article is to review primary graft dysfunction, acute rejection, and chronic rejection with emphasis on the role of imaging, pathology findings, and differential diagnosis.

Critical Care after Lung Transplantation

Since the first successful lung transplantation in 1983, there have been many advances in the field. Nevertheless, the latest data from the International Society for Heart and Lung Transplantation revealed that the risk of death from transplantation is 9%. Various aspects of postoperative management, including mechanical ventilation, could affect intensive care unit stay, hospital stay, and immediate postoperative morbidity and mortality. Complications such as reperfusion injury, graft rejection, infection, and dehiscence of anastomosis increase fatal adverse side effects immediately after surgery. In this article, we review the possible immediate complications after lung transplantation and summarize current knowledge on prevention and treatment.

Acute rejection

Despite induction immunosuppression and the use of aggressive maintenance immunosuppressive regimens, acute allograft rejection following lung transplantation is still a problem with important diagnostic and therapeutic challenges. As well as causing early graft loss and mortality, acute rejection also initiates the chronic alloimmune responses and airway-centred inflammation that predispose to bronchiolitis obliterans syndrome (BOS), also known as chronic lung allograft dysfunction (CLAD), which is a major source of morbidity and mortality after lung transplantation. Cellular responses to human leukocyte antigens (HLAs) on the allograft have traditionally been considered the main mechanism of acute rejection, but the influence of humoral immunity is increasingly recognised. As with other several other solid organ transplants, antibody-mediated rejection (AMR) is now a well-accepted and distinct clinical entity in lung transplantation. While acute cellular rejection (ACR) has defined histopathological criteria, transbronchial biopsy is less useful in AMR and its diagnosis is complicated by challenges in the measurement of antibodies directed against donor HLA, and a determination of their significance. Increasing awareness of the importance of non-HLA antigens further clouds this issue. Here, we review the pathophysiology, diagnosis, clinical presentation and treatment of ACR and AMR in lung transplantation, and discuss future potential biomarkers of both processes that may forward our understanding of these conditions.