Protocol biopsies should be standard of care for pediatric renal allograft recipients!

Early surveillance biopsy utilization and management of pediatric renal allograft acute T cell-mediated rejection in Canadian centers: Observations from the PROBE multicenter cohort study

BACKGROUND

Early TCMR surveillance with protocol kidney biopsy is used differentially among pediatric kidney transplant centers. Little has been reported about actual center-based differences, and this variability may influence TCMR ascertainment, treatment, and monitoring more broadly.

METHODS

Data from the PROBE multicenter study were used to identify patients from centers conducting ESB or LSIB. ESB was defined as >50% of patients having at least 1 surveillance biopsy in the first 9 months. Patients were compared for number of biopsies, rejection episodes, treatment, and follow-up monitoring.

RESULTS

A total of 261 biopsies were performed on 97 patients over 1-2 years of follow-up. A total of 228 (87%) of biopsies were performed in ESB centers. Compared to LSIB centers, ESB centers had 7-fold more episodes of TCMR diagnosed on any biopsy [0.8 ± 1.2 vs 0.1 ± 0.4; P < .001] and a 3-fold higher rate from indication biopsies [0.3 ± 0.9 vs 0.1 ± 0.3; P = .04]. The proportion of rejection treatment varied based on severity: Banff borderline i1t1 (40%);>i1t1 and < Banff 1A (86%); and ≥ Banff 1A (100%). Biopsies for follow-up were performed after treatment in 80% of cases (n = 28) of rejection almost exclusively at ESB centers, with 17 (61%) showing persistence of TCMR (≥i1t1).

CONCLUSIONS

Practice variation exists across Canadian pediatric renal transplant centers with ESB centers identifying more episodes of rejection. Additionally, treatment of Banff borderline is not universal and varies with severity regardless of center type. Lastly, follow-up biopsies are performed inconsistently and invariably show persistence of rejection.

Surveillance biopsies in children post-kidney transplant

Surveillance biopsies are increasingly used in the post-transplant monitoring of pediatric renal allograft recipients. The main justification for this procedure is to diagnose early and presumably modifiable acute and chronic renal allograft injury. Pediatric recipients are theoretically at increased risk for subclinical renal allograft injury due to their relatively large adult-sized kidneys and their higher degree of immunological responsiveness. The safety profile of this procedure has been well investigated. Patient morbidity is low, with macroscopic hematuria being the most common adverse event. No patient deaths have been attributed to this procedure. Longitudinal surveillance biopsy studies have revealed a substantial burden of subclinical immunological and non-immunological injury, including acute cellular rejection, interstitial fibrosis and tubular atrophy, microvascular lesions and transplant glomerulopathy. The main impediment to the implementation of surveillance biopsies as the standard of care is the lack of demonstrable benefit of early histological detection on long-term outcome. The considerable debate surrounding this issue highlights the need for multicenter, prospective, and randomized studies.

Treatment strategies to minimize or prevent chronic allograft dysfunction in pediatric renal transplant recipients: an overview

Long-term allograft survival poses a major problem in pediatric renal transplantation, with allograft nephropathy being the principal cause of graft failure after the first post-transplant year. The mechanisms of nephron loss resulting in graft dysfunction are multiple, comprising both immunologic factors such as acute and chronic antibody- or T-cell-mediated rejection and non-immunologic components. The latter include peri-transplant injuries and renovascular lesions (renal artery stenosis, thrombosis) as well as cardiovascular risk factors such as arterial hypertension and hyperlipidemia. Another relevant issue leading to progressive nephron loss and declining kidney transplant function is acute and chronic nephrotoxicity induced by the calcineurin inhibitors (CNIs) ciclosporin (cyclosporine microemulsion) and tacrolimus. Furthermore, the presence of an abnormal lower urinary tract as well as bacterial (recurrent pyelonephritis) and viral (cytomegalovirus [CMV], polyomavirus [BK virus; BKV]) infections are crucial factors involved in the incidence of chronic allograft dysfunction and graft failure. Renovascular lesions and lower urinary tract obstruction are typical indicators for surgical intervention. The aim of treatment in pediatric patients with renal failure secondary to a dysfunctional lower urinary tract is to create a sterile, continent, and nonrefluxive reservoir. Surgical techniques such as bladder augmentation and the introduction of intermittent catheterization and anticholinergic therapy have significantly improved graft outcome. Arterial hypertension, another factor responsible for graft function deterioration in pediatric renal transplant recipients, is controlled preferably by the use of angiotensin converting enzyme (ACE) inhibitors or angiotensin II receptor antagonists, which are known to possess nephroprotective properties in addition to their potent antihypertensive effects. Although treatment of subclinical rejection with augmented immunosuppression has been associated with better graft survival, an increase of the immunosuppressive level to avoid subclinical rejection should be weighed against the risk of infection. The majority of viral infections affecting kidney allografts are caused by CMV and BKV. Antiviral CMV prophylaxis or pre-emptive therapy with ganciclovir has been shown to have beneficial effects in the pediatric renal transplant population. Treatment of BKV-induced nephropathy is based on reduction of the immunosuppressant therapy, although specific antiviral agents such as cidofovir and leflunomide are known to inhibit BKV. However, cidofovir itself is nephrotoxic and should therefore be administered cautiously to pediatric renal transplant patients. Since CNIs are likewise known for their nephrotoxic effects, especially with long-term use, alteration of the immunosuppressant regimen is necessary in case of deteriorating graft function due to CNI-induced histopathologic changes. Complete CNI avoidance seems inappropriate because, in this situation in pediatric renal transplant recipients, other relatively potent immunosuppressant agents such as lymphocyte-depleting antibodies, which are frequently accompanied by a higher incidence of infections, are needed for rejection prophylaxis. CNI withdrawal and switching of the immunosuppressant regimen from CNI therapy to sirolimus may be an option for some pediatric renal transplant patients with less advanced graft function deterioration. Nevertheless, potential adverse events such as aggravation of proteinuria, hyperlipidemia, myelosuppression, and hypergonadotropic hypogonadism have to be considered, and controlled studies are lacking. At present, an immunosuppressant maintenance therapy composed of low-dose tacrolimus or ciclosporin (CNI minimization) and mycophenolate mofetil with low-dose corticosteroids appears to be the most promising strategy to adopt in pediatric renal transplant recipients at low or normal immunologic risk.

Long-term outcome of pediatric renal transplantation: the Norwegian experience in three eras 1970-2006

During the years 1970-2006, 251 renal transplantations were performed in 178 children in Norway. The proportion of LD was 84%. Transplantations were performed preemptively in 52%. Pretransplant dialysis time was median three months. Structural abnormalities and hereditary renal disorders constituted 69% of end-stage renal diseases, 29% were caused by glomerulopathies and other acquired disorders and 2% of unknown cause. Patient survival rates were 94.2, 93.5, and 84.4% at five, 10, and 20 yr, respectively. The most frequent cause of death was infections followed by cardiovascular events. For recipients of living donor grafts (n = 149), survival of first transplant was 82, 68.8, and 45.1% at five, 10, and 20 yr, respectively, and was significantly higher than for recipients of deceased donor organs (n = 29; log rank, p = 0.008). The only significant predictor for better transplant survival when modeled with multiple regression analysis adjusted for pretransplant dialysis, diagnosis, donor age, sex and immunosuppressive era, was the use of LD compared with DD (HR = 2.1, 95% CI [1.1-4.0], p = 0.02). The acute rejection rate declined significantly from 61.5% in 1970-1982 to 14.5% in 2000-2006 (log rank, p = 0.002). It remains to be seen whether the reduction in acute rejection rate and present immunosuppressive therapy will have a positive impact on long-term graft survival in years to come.

Early treatment of acute rejections gives favorable long-term function after renal transplantation in small children

AR is considered as a risk factor for CAN after kidney TX. We combined data on AR with long-term graft function and histopathology to assess whether early treatment of AR is beneficial for long-term graft outcome in small children. Seventy-seven children with a mean age of 4.7 yr were studied. Early AR were diagnosed with FNAB and treated with methylprednisolone already before clinical signs occurred. The children were grouped into three groups (clinical, subclinical, and no AR) and then followed prospectively up to seven yr after TX with measured GFR and core needle biopsies to assess histopathological findings with the CADI score. Early AR, whether clinical or subclinical, did not affect long-term graft survival (80% with AR vs. 83% without AR, at 10 yr). Late AR, more than one yr after TX, had an inferior graft survival 50% vs. 84% (p = 0.02). GFR declined and the CADI scores increased with time, but there were no significant differences between the three groups. Prompt and early treatment of post-operative AR gives favorable long-term graft function compared with children without AR. Late AR is a risk factor for inferior long-term graft function.

Surveillance renal transplant biopsies and subclinical rejection at three months post-transplant in pediatric recipients

Subclinical acute rejection (SCR) has been increasingly recognized in adult renal transplant recipients with the advent of surveillance biopsies. However, in children, surveillance biopsies are not routinely performed at most centers. Therefore, the incidence, predisposing factors, treatment, and clinical outcomes of SCR remain unclear in children. From August 2004 to December 2005, we performed 36 protocol biopsies at three months post-transplantation. All patients had received induction therapy with basiliximab and were maintained on prednisone, MMF, and tacrolimus. Sixteen cases of SCR were detected by biopsy (44%). Age, gender, race, donor source, or serum creatinine did not discriminate between children with SCR and those with normal biopsies. All cases of SCR were treated with high doses of methylprednisolone. At one yr post-transplant, renal function was similar in children with SCR to those with normal surveillance biopsies (p = 0.62). Because of the high incidence of SCR, the maintenance dose of MMF was increased by 50% in 20 children transplanted after December 2005. This resulted in a significant decline in the incidence of SCR from 44 to 15% (p < 0.05). However, the incidence of polyomavirus (BK) viremia also increased significantly in these children (p < 0.005).

CONCLUSION

A high incidence of SCR was found on surveillance biopsies at three months post-transplant and could not be predicted by age, gender, race, donor source, or serum creatinine. The occurrence of SCR declined significantly by increasing the dose of MMF, but resulted in an increase in BK viremia. We conclude that surveillance biopsies provide valuable information in the management of pediatric renal transplant recipients. Increasing immunosuppression to avoid SCR should be weighed against the risk for infection.

Low incidence of adverse events in outpatient pediatric renal allograft biopsies

In 1999, our center implemented a policy of outpatient protocol biopsies as standard practice for the clinical management of pediatric renal allograft recipients. In order to determine the safety of this procedure, we conducted a retrospective chart audit of all outpatient renal allograft biopsies performed at our center. Biopsies were performed under conscious (midazolam) or procedural (propofol/fentanyl) sedation. Localization of the lower pole of the renal allograft was achieved with renal ultrasound. Using a Biopty gun with a 16-gauge needle, two cores were obtained. Patients were discharged four h post-biopsy. Patient demographics, hospital length of stay (LOS), specimen adequacy (per Banff criteria) and major and minor adverse events were recorded in a central database. Data were expressed as mean +/- SD. From June 1999 to July 2004, we performed 162 biopsies in 43 pediatric renal allograft recipients. Most patients underwent extraperitoneal transplantation (42/43, 97.7%) and were greater than five yr of age at biopsy (129/131 biopsies, 98.5%). The majority of these procedures (131/162, 80.9%) were conducted in the outpatient department, with 113 of 131 (86.3%) being obtained for protocol (n = 89) and one-month follow-up acute rejection therapy (n = 24) indications. Patients underwent 3.7 +/- 2.7 biopsies (range = 1-11). Specimen adequacy was achieved in 119 of 124 (96.0%) of documented cases. The overall incidence of adverse events was 12 of 131 (9.2%) biopsies, all of which were minor in severity. Macroscopic hematuria was the most common minor adverse event, occurring after 11 of 131 (8.4%) biopsies. While macroscopic hematuria prolonged LOS (adverse events vs. no adverse events: 23.0 +/- 26.0 vs. 8.6 +/- 4.1 h, p = 0), none of these episodes required major surgical or radiographic interventions. We conclude that in patients greater than five yr of age with extraperitoneal renal allografts, outpatient protocol biopsies using a 16-gauge needle are sufficiently safe to justify their inclusion in the routine clinical management of pediatric renal allograft recipients and in pediatric clinical trials.