Course of renal allograft histopathology after transplantation in early childhood

Introducing a New Technique for Fascial Closure to Avoid Renal Allograft Compartment Syndrome in Pediatric Recipients: The Use of Tutoplast® Fascia Lata

Introduction

Renal allograft compartment syndrome (RACS) is a complication that infrequently occurs after renal transplantation. Tight muscle closure may lead to RACS due to compression of renal parenchyma or kinking of the renal vessels. Many techniques have been proposed in an attempt to achieve tension-free closure, which can be specially challenging in child recipients. We present our experience with Tutoplast^® Fascia Lata (RTI Surgical Tutogen Medical GmbH Industriestrasse 6, 91077 Neunkirchen am Brand, Germany) closure.

Methods

All pediatric patients who underwent renal transplantation in our center between 2012 and 2021 were reviewed. Eight patients with Tutoplast^® Fascia Lata placed at the time of initial transplantation were identified. Donor and recipient characteristics, Doppler ultrasound findings, and overall patient and graft survival rates were analyzed.

Results

Doppler ultrasound was performed intra-operatively after abdominal wall closure. If any sign of vascular compromise was seen, the abdominal wall was opened and the graft was revised. The Tutoplast^® Fascia Lata implant was used to perform tension-free fascia closure and, afterwards, a Doppler ultrasound was performed to confirm the optimal renal artery perfusion and venous patency. Three of the renal transplantations were from a cadaver donor, with two of them en bloc. Living donor transplantation was performed in four cases. Among which, there was a case of auto-transplantation due to bilateral renal artery stenosis. None of the patients presented any complications of either short or long term that was derived from the abdominal closure with Tutoplast^® Fascia Lata. There was also no record of graft failure till datum.

Conclusions

Restricted volume of the recipient pelvic cavity and the size discrepancy between the recipient pelvic cavity space and the donor adult kidney may lead to RACS. Other situations that occur more infrequently, i.e., as en bloc or auto-transplantation, are prone to suffer the same problem. Tutoplast^® Fascia Lata is a safe option for these patients.

Is there a functional disadvantage to using the external iliac vessels for vascular anastomosis in children and adolescents undergoing renal transplantation?

PURPOSE

RT remains the best available strategy for addressing stage 5 chronic kidney disease in children and adolescents. Technical aspects of the procedure can have a clear impact on complications and health of the allograft, including DGF. Immediate optimal perfusion is paramount, thus choosing a target vessel has to take into account the flow demands imposed by an adult-size kidney in a proportionally smaller recipient. Herein, we explore the hypothesis that vascular anastomosis location can impact DGF adjusting for patient age and body size.

METHODS

Retrospective review of a single institution referral center transplant database, including information on 156 patients. We collected data on patient characteristics (age, height, BSA, gender, preoperative need for dialysis), donor source (deceased vs living), WIT/CIT, hemodynamics during the procedure, use of inotropes or diuretics, and location of the arterial and venous anastomoses. The primary outcome, DGF, was assessed by measuring the ttNC (in days), adjusting for age and BSA.

RESULTS

Location of the arterial anastomosis was clearly impacted by age and donor size (Figure 1A). On univariate analyses, longer ttNC was associated with deceased vs living donor (11.8 ± 11.5 and 4.3 ± 5.0; P < 0.001), preoperative need for dialysis (9.7 ± 11.0 and 6.5 ± 6.0, P = 0.02), location of arterial anastomosis (aorta [n = 21] 4.9 ± 6.1, common iliac [n = 93] 7.1 ± 7.3, external iliac 14.7 ± 14.5; P < 0.001, Figure 1B) and venous anastomosis (vena cava [n = 21] 5.6 ± 6.3, common iliac [n = 89] 7.1 ± 7.6, external iliac [n = 44] 13.8 ± 14); P < 0.001). On multivariable analysis, this association remained statistically significant when adjusting for recipient age, height, BSA, donor source, change in blood pressure with unclamping, and use of inotropes and preoperative dialysis. The detrimental effect on ttNC was more salient when comparing external iliac vs common iliac and aorta or vena cava.

CONCLUSION

Our data suggest that anastomosis to a smaller caliber target vessel (ie, external iliac) in comparison with the common iliac or aorta/vena cava may be a risk factor for delayed return of graft function, independent of recipient size and donor source. This finding merit further evaluation, as it may help with intraoperative decision making during pediatric and adolescent RT.

Subclinical inflammation and chronic renal allograft injury in a randomized trial on steroid avoidance in pediatric kidney transplantation

Steroid avoidance is safe and effective in children receiving kidney transplants in terms of graft function and survival, but the effects on allograft histology are unknown. In this multicenter trial, 130 pediatric renal transplant recipients were randomized to steroid-free (SF; n = 60) or steroid-based (SB; n = 70) immunosuppression, and underwent renal allograft biopsies at the time of graft dysfunction and per protocol at implantation and 6, 12 and 24 months after transplantation. Clinical follow-up was 3 years posttransplant. Subclinical acute rejection was present in 10.6% SF versus 11.3% SB biopsies at 6 months (p = 0.91), 0% SF versus 4.3% SB biopsies at 1 year (p = 0.21) and 0% versus 4.8% at 2 years (p = 0.20). Clinical acute rejection was present in 13.3% SF and 11.4% SB patients by 1 year (p = 0.74) and in 16.7% SF and 17.1% SB patients by 3 years (p = 0.94) after transplantation. The cumulative incidence of antibody-mediated rejection was 6.7% in SF and 2.9% in SB by 3 years after transplantation (p = 0.30). There was a significant increase in chronic histological damage over time (p < 0.001), without difference between SF and SB patients. Smaller recipient size and higher donor age were the main risk factors for chronic histological injury in posttransplant biopsies.

Stanniocalcin supports the functional adaptation of adult-sized kidneys transplanted into the pediatric recipients

BACKGROUND

The functional adaptation of adult-sized kidney (ASK) grafts to the recipient's size is not completely reversible and is associated with irreversible histologic damage in the smallest recipients. The aim of the study was to unveil the molecular mechanisms underlying the functional adaptation of ASK transplants to small pediatric recipients.

METHODS

Because physiologic and functional adaption of ASK in infants is seen maximally at 3 months after transplantation, we selected 21 pediatric recipients of an ASK with protocol biopsies at engraftment and 3 and 6 months, without delayed graft function or interval rejection, and we conducted whole-genome expression profiles of the renal allograft biopsies at 3 months and correlated results with subsequent absolute glomerular filtration rate (aGFR).

RESULTS

Seven hundred twenty-four unique genes correlated significantly with aGFR (q value <5%). Canonical pathway analysis identified overrepresentation of relevant pathways involved in regulation of tubular salt reabsorption and enzymatic pathways for organ development and hypertrophy. The single gene that correlated best with aGFR was stanniocalcin 1 (STC1). STC1 expression also correlated with the recipient's size at the time of transplantation and the chronic allograft damage index at 6 months.

CONCLUSIONS

Functional adaptation of adult-sized grafts to the pediatric recipient is associated with molecular adaptation for normal-volume homeostasis of the recipient. Our finding also suggests that stanniocalcin (STC1) plays an important role on functional adaption in pediatric kidney transplantation.

Patterns of chronic injury in pediatric renal allografts

BACKGROUND

In pediatric recipients, the pathophysiology of chronic renal allograft injury is poorly understood.

METHODS

We studied the evolution and determinants of tubulointerstitial, vascular, and glomerular injury in 240 pediatric protocol renal allograft biopsies during the first 5 years posttransplant.

RESULTS

Chronic tubulointerstitial injury (ci, ct) developed predominantly during the first 12 months posttransplant, whereas chronic vascular damage (cv, and arteriolar hyalinosis [ah]) and global glomerulosclerosis (gs) became increasingly prevalent at 25 to 36 months and beyond. Chronic interstitial lesions were associated with acute rejection and borderline histology (odds ratio [OR] 2.3, P<0.04), recipient body surface area less than 1.0 m2 (OR 3.6, P<0.05), and obesity (OR 2.0, P<0.03). Determinants of ct were acute rejection (OR 2.6, P=0.02) and acute tubular necrosis (OR 2.8, P<0.04). Vascular fibrous intimal thickening and ah were associated with donor hypertension (OR 3.6, P=0.001) and recipient body surface area less than 1.0 m (OR 2.6, P=0.02), respectively. The severity of ah correlated with the incidence of gs (r=0.32, P<0.0001), with 7.8% gs for ah0, 14.3% gs for ah1, 60.0% gs for ah2, and 95.5% gs for ah3 (median values). Antibody induction conferred protection from ci (OR 0.31, P=0.008), ct (OR 0.33, P=0.002), and ah (OR 0.12, P<0.001) progression.

CONCLUSIONS

By 5 years posttransplant, pediatric renal allografts manifest a substantial burden of tubulointerstitial and microvascular injury. These lesions are associated with donor hypertension, acute inflammation, renal hypoperfusion, obesity, and calcineurin inhibitor toxicity. The pervasiveness and rapid progression of microvascular lesions at 25 to 36 months suggest that attempts at reducing calcineurin inhibitor exposure should be made before two years posttransplant.

Chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is the leading cause of renal allograft loss in paediatric renal transplant recipients. CAN is the result of immunological and nonimmunological injury, including acute rejection episodes, hypoperfusion, ischaemia reperfusion, calcineurin toxicity, infection and recurrent disease. The development of CAN is often insidious and may be preceded by subclinical rejection in a well-functioning allograft. Classification of CAN is histological using the Banff classification of renal allograft pathology with classic findings of interstitial fibrosis, tubular atrophy, glomerulosclerosis, fibrointimal hyperplasia and arteriolar hyalinosis. Although improvement in immunosuppression has led to greater 1-year graft survival rates, chronic graft loss remains relatively unchanged and opportunistic infectious complications remain a problem. Protocol biopsy monitoring is not current practice in paediatric transplantation for CAN monitoring but may have a place if new treatment options become available. Newer immunosuppression regimens, closer monitoring of the renal allograft and management of subclinical rejection may lead to reduced immune injury leading to CAN in the paediatric population but must be weighed against the risk of increased immunosuppression and calcineurin inhibitor nephrotoxicity.

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.

The evolution of nonimmune histological injury and its clinical relevance in adult-sized kidney grafts in pediatric recipients

To describe the evolution, risk factors and impact of nonimmune histological injury after pediatric kidney transplantation, we analyzed 245 renal allograft protocol biopsies taken regularly from the time of transplantation to 2 years thereafter in 81 consecutive rejection-free pediatric recipients of an adult-sized kidney. Isometric tubular vacuolization was present early after transplantation was not progressive, and was associated with higher tacrolimus pre-dose trough levels. Chronic tubulo-interstitial damage and tubular microcalcifications were already noted at 3 months, were progressive and had a greater association with small recipient size, male donor gender, higher donor age and female recipient gender, but not with tacrolimus exposure. Renal function assessment showed that older recipients had a significant increase in absolute glomerular filtration rate with time after transplantation, which differed from small recipients who showed no increase. It is concluded that progressive, functionally relevant, nonimmune injury is detected early after adult-sized kidney transplantation in pediatric recipients. Renal graft ischemia associated with the donor-recipient size discrepancy appears to be a greater risk factor for this chronic histological injury, suggesting that the exploration of additional therapeutic approaches to increase allograft perfusion could further extend the graft survival benefit of adult-sized kidneys transplanted into small children.

Plasma exchange and retransplantation in recurrent nephrosis of patients with congenital nephrotic syndrome of the Finnish type (NPHS1)

BACKGROUND

Recurrent nephrotic syndrome (NS) is a severe problem after renal transplantation in patients with congenital nephrotic syndrome of the Finnish type (NPHS1). The NPHS1 kidneys do not express nephrin, and antibodies against this major glomerular filter protein have been observed in NPHS1 children with recurrent NS. We evaluated here the use of plasma exchange (PE) therapy and kidney retransplantation in NPHS1 patients with recurrent NS and extended our studies on the pathogenesis of the recurrence.

METHODS

Clinical data on 65 NPHS1 patients who received 77 kidney transplants between the years 1986 and 2006 was collected. Serum anti-nephrin antibodies were assayed with an enzyme-linked immunosorbent assay method, and the kidney biopsy samples were evaluated by light microscopy and immunohistochemistry.

RESULTS

Twenty-three episodes of recurrent NS occurred in 19 grafts of 13 NPSH1 patients homozygous for Fin-major mutation. Six retransplantations were performed to four NPHS1 patients, who lost their graft because of recurrent NS, and heavy proteinuria developed immediately in all cases. Although 73% of the patients had detectable serum anti-nephrin antibodies, the kidney biopsy findings were minimal. Introduction of PE alongside cyclophosphamide proved effective in the treatment of the proteinuric episodes (one graft loss out of nine). If remission was achieved, recurrent NS did not significantly deteriorate the long term graft function.

CONCLUSIONS

The clinical and pathological data suggest that anti-nephrin antibodies effectively impair the glomerular function in kidney grafts of NPHS1 patients homozygous for Fin-major mutation. Plasma exchange is a useful adjunct to the treatment of the recurrent NS.

Chronic allograft nephropathy in paediatric renal transplantation

Chronic allograft nephropathy (CAN) is now the leading cause of renal transplant loss in paediatric transplant recipients. Despite improvements in immunosuppression, which have significantly reduced the incidence of acute rejection, the rates of chronic kidney loss have remained unchanged in paediatric transplant patients over the last 20 years. Chronic allograft nephropathy is a pathological diagnosis of which the key features are tubular atrophy and interstitial fibrosis. More consistent definitions and grading of these through the Banff classification have allowed more rigorous study of the development of chronic allograft nephropathy along with further identification of specific lesions associated with the underlying aetiologies. While initially thought to be primarily due to immune injury, it is now evident that CAN is the end result of a variety of immune and non-immune injuries including ischaemia reperfusion injury, calcineurin inhibitor (CNI) toxicity and infections. Protocol biopsy studies have demonstrated rates of CAN development in children similar to those in adults with comparable underlying pathological processes. This review outlines the current knowledge of CAN within the context of paediatric renal transplantation.

An image analysis-based method for quantification of chronic allograft damage index parameters

Chronic allograft damage index (CADI) is a semi-quantitative histopathological score that predicts renal graft outcome. We aimed to develop an objective image analysis-based method for quantification of CADI parameters. Thirty-five kidney transplant biopsies were visually analyzed according to the original CADI criteria, and divided into normal, mildly, moderately and severely altered groups. Digital images of the same samples were then analyzed with IPLab software. Areas of inflammation and fibrosis measured using image analysis increased simultaneously with corresponding visual scores, although the difference between non-inflamed and mildly inflamed groups was not statistically significant. Area of normal tubuli decreased in the images of samples with visually mild/moderate tubular atrophy and tended to be even smaller in the group with severe tubular atrophy. Image analysis-based glomerular sclerosis score increased concurrently with increasing visual score. Mesangial matrix increase score in image analysis was greater in the samples with visually mild/moderate mesangial matrix increase score compared to those with normal glomeruli, and it was highest in the group with severe mesangial matrix increase. An image analysis-based CADI scoring of renal allograft biopsies could provide more precise data for scientific studies, and help pathologists in renal allograft biopsy scoring.

Better renal function with enhanced immunosuppression and protocol biopsies after kidney transplantation in children

Subclinical rejection may be associated with decreased graft function after renal transplantation (Tx). Detection by protocol biopsies and treatment could thus be important for the long-term prognosis. We have earlier discovered that glomerular filtration rate (GFR) declined in young children during the first 18 months. Consequently, we slightly enhanced and individualized each patient's immunosuppression. This was a retrospective study of 59 pediatric renal Tx patients between 1995 and 2001. The 35 historical controls received triple-therapy of azathioprine, methylprednisolone and cyclosporine. GFR was measured by protocol at discharge, 6 and 18 months, and a core biopsy was obtained at 18 months. The 24 study patients in addition received basiliximab, had GFR measured at 3 and 12 months, and a biopsy taken at 3 months. Based on histology and function, immunosuppression was individually adjusted. The groups were compared for GFR and histology at 18 months after Tx. There were less acute rejection episodes in the study group (0.38 vs. 1.23 per patient) and serum creatinine concentrations were lower. Subclinical rejection was detected and treated in 39% at 3 months. There were more chronic changes in the control (47%) than in the study group (29%) at 18 months. GFR was significantly higher in the study group at 18 months (87 vs. 68 mL/min/1.73 m(2)), most remarkably in patients < or =2 yr of age (99 vs. 68 mL/min/1.73 m(2)). Detection of subclinical rejection and slightly enhanced and individualized immunosuppression improved GFR 18 months after renal Tx, especially in the youngest patients.

Cyclosporine A monitoring--how to account for twice and three times daily dosing

Cyclosporine A (CsA) dose-interval pharmacokinetic profiles, performed 1-4 years post-transplantation, were collected from 74 renal transplanted children. Forty patients were on three times daily dosing (t.i.d.) and 34 on twice daily dosing (b.i.d.). Regression models for prediction of area under the curve (AUC) using 1-3 concentration time points as independent variables were developed. With similar weight-adjusted single doses (mg kg(-1)) of CsA, t.i.d. dosing resulted in a trough-concentration (C0) similar to that from b.i.d. dosing, but a 30% lower 2 h post-dose concentration (C2). For b.i.d. dosing the relationship between C0 and AUC was poor (r2=0.23) and the prediction error was large (5.8+/-33.5%). For t.i.d. dosing the relationship was better (r2=0.79), but prediction error was still large (4.5+/-24.9%). For C2 relationships were similar to those for the b.i.d. (r2=0.59) and t.i.d. (r2=0.63) groups, but explained modestly the variations of AUC (prediction error=2.6+/-16.8% b.i.d., 4.8+/-23.2% t.i.d.). Both C0 and C2 are useful monitoring methods when CsA is administered t.i.d. If the aim is similar specified daily drug exposure, the target C2 should be roughly 30% smaller in t.i.d. dosing than in b.i.d. dosing and the target C0 could be similar. The prediction error of AUC can be large in individual patients when using single time-point determinations, however. The use of multiple time points reduces the variation, but is less feasible.

Surveillance biopsies are superior to functional studies for the diagnosis of acute and chronic renal allograft pathology in children

In this report of our 3-yr protocol biopsy program, we describe the evolution of acute rejection (AR) and chronic renal allograft nephropathy (CAN) in a cohort of 21 children treated with antibody induction, tacrolimus, mycophenolate mofetil, and prednisone. The aims of this study were to compare the pathogenicity of clinical acute rejection (CAR) and subclinical acute rejection (SAR), and to determine whether functional studies accurately represent acute and chronic renal allograft pathology in pediatric recipients with disproportionately large grafts. Using concurrent biopsies, we evaluated: (i) the utility of changes in the baseline sCr (DeltasCr) to predict both the onset of AR and the response to immunosuppressive therapy; and (ii) the relationship of the calculated creatinine clearance and the presence of pathologic proteinuria to the severity of CAN. We performed 112 biopsies: 11 donor, 73 protocol, 16 acute graft dysfunction and 12 1-month follow-up AR therapy. CAR and SAR were similar in incidence, timing and histologic severity. Progression of CAN was associated with the first episode of CAR (p < 0.02) and the cumulative number of episodes of CAR (p < 0.01), SAR (p < 0.05), CAR plus SAR (p < 0.002) and borderline SAR (B-SAR) (p < 0.006). One-month post-treatment DeltasCrs could not distinguish 1-month follow-up biopsies with histologically confirmed worsened or unchanged AR from those with improved histology (35.2 +/- 74.8% vs. 23.8 +/- 24.9%, p = NS). These findings led to the addition of anti-lymphocyte antibody therapy in five of 10 (50%) cases. Despite 100% 3-yr actuarial graft survival and excellent function (GFR = 111 +/- 36 mL/min/1.73 m(2)), 18 of 21 (86%) patients had grade I CAN or greater chronic histology at a mean +/- sd follow-up period of 18.2 +/- 13.1 months. Thirteen of 21 (62%) patients progressed to grade I CAN at 5.2 +/- 3.6 months and five (38%) of these patients progressed to grade II CAN at 17.8 +/- 11.3 months. Schwartz GFR did not differ between patients with or without CAN (108 +/- 38 mL/min/1.73 m(2) vs. 127 +/- 8 mL/min/1.73 m(2), p = NS). In biopsies with CAN and no associated AR, neither the Banff chronic tubulointerstitial (Banff ci) score nor the Banff chronic grade correlated with the GFR. Proteinuria was not associated with CAN. Clinical AR and SAR are similar histologic lesions with a capacity for CAN progression. In pediatric renal transplant recipients, longitudinal protocol biopsies are superior to functional studies for the diagnosis and post-therapeutic monitoring of AR and for the surveillance of CAN.

Predictive value of pretransplantation cyclosporine pharmacokinetic studies on initial post-transplantation dosing in pediatric kidney allograft recipients

Despite the introduction of a variety of new immunosuppressive agents, cyclosporine A (CsA) has maintained a strong position in pediatric transplantation (Tx). Post-Tx dosing with CsA is a challenging task because of the narrow therapeutic window of the drug, the great individual variability of metabolism and the lack of consensus about the optimal dosage and targeted blood concentration. Sufficient administration of CsA may be protective against acute rejections and other early complications after Tx, which is crucial for the long-term survival of the graft. Individual doses based on pre-Tx pharmacokinetic studies might be helpful in achieving optimal early concentrations of CsA. To asses the usefulness of pharmacokinetic studies, we retrospectively compared the post-Tx doses administered with the individually predicted doses between 1988 and 1998. Multiple regression of data on 65 de novo renal transplant recipients, 1.1-15.5 yr old, was used to analyze the significance of the predicted dose, trough blood concentration of CsA (B-CsA), serum creatinine and age at the time of Tx in explaining the doses used during the first three post-Tx weeks. Patients were grouped according to age (<2, 2-8 and >8 yr), according to the predicted dose (within or outside +/-25% of age-group average), and according to the oral formulation of CsA. Standard dosing scheme was simulated by using age-specific average doses in the place of the individual predicted doses. Administered doses of CsA were high [averaging 22.6 (504), 20.7 (484), and 12.4 mg/kg/d (329 mg/m2/d) for patients <2, 2-8, and >8 yr old] but the average B-CsA remained in the target range of 250-450 microg/L. The predicted dose and age were significant parameters in explaining the administered doses during the first 3 wk after Tx. B-CsA and S-creatinine were non-significant. The predicted doses were used to initiate the dosing of CsA after Tx (R2 = 0.70) and adjustments to dosing were made during the next weeks (R2 = 0.59, 0.52). Multiple regression model showed better fit for 60% of our patients, who had atypical predicted doses (R2 = 0.74, 0.60, 0.64 for first, second and third post-Tx weeks, respectively), most remarkably in patients <2 yr of age, than for the study population as a whole. A simulated standard dose was not able to explain the administered doses of CsA. In conclusion, pre-Tx pharmacokinetic studies are valuable for determining individual post-Tx starting doses, especially for those patients who need high or low doses of CsA. Individual dosing led to relatively high initial CsA doses, which could be significant for the long-term survival of the graft.

Rejection and recipient age

In transplantation the risk of acute rejection decreases with recipient age. This is clearly illustrated in transplantation of a non-vascularised tissue, such as the cornea. In vascularised transplants, such as kidneys, acute rejection decreases with recipient age, but the phenomenon is obscured by the fact that chronic allograft nephropathy increases with age, and is further confounded by increased death from infectious disease and drug-related causes. The underlying cellular mechanisms responsible for this weakening of rejection are discussed, as is defective signal transduction leading to decreased activation of cells and decreased resistance to immunosuppressive drugs. This supports a view that less intensive immunosuppressive drug therapy is desirable in elderly recipients. Although pharmacokinetic studies are documented, there are no routine assays to measure efficacy of these drugs in individual patients. In summary, the decline in acute rejection with increasing recipient age may be due both to immunosenescence and decreased resistance to immunosuppressive drugs. Future assays to test these mechanisms could be used to tailor therapy to individual needs.

Fine-needle aspiration biopsy allows early detection of acute rejection in children after renal transplantation

analysis detected rejections often before clinical signs. Half of the patients had increased serum creatinine concentration and 38% had fever at the time of rejection diagnosis. Both signs were present in only 19% of the episodes. A decrease in urine output (>20%) was seen in a third of the episodes. The rejections responded well to oral methylprednisolone (3 mg/kg/day), and lymphoglobulins were needed in only 12% of the episodes. More than 90% of the rejections were completely reversible and no transplant was lost because of acute rejection.

CONCLUSION

The results indicate that FNAB is a safe and sensitive method for the diagnosis and follow-up of acute cellular rejection in pediatric recipients of different ages.

Adult-size kidneys without acute tubular necrosis provide exceedingly superior long-term graft outcomes for infants and small children: a single center and UNOS analysis. United Network for Organ Sharing

BACKGROUND

Infants with end-stage renal disease are at highest risk for early graft loss and mortality of any subgroup undergoing renal transplantation. This study evaluates the influence of donor tissue mass and acute tubular necrosis (ATN) on graft survival and incidence of acute rejection episodes in infant and small child recipients of living donor (LD) and cadaver (CAD) adult-size kidneys (ASKs), pediatric CAD kidneys and combined kidney-liver transplants. Methods. Kidney transplants in infants and small children at a single center and those reported to the UNOS Scientific Renal Transplant Registry were analyzed. At Stanford, multi-variate analysis was conducted on 45 consecutive renal allograft recipients weighing < or = 15 kg, mean weight 11.2 +/- 2.6 kg. The UNOS Registry results in age groups 0-2.5 (n=548) and 2.5-5 years (n=743) were compared with age groups 6-12, 13-18, and the lowest risk adult group of 19-45 years. STANFORD RESULTS. Graft survival was 97.8 +/- 0.0 at 2 years and 84.6 +/- 0.1% at 8 years. The incidence of biopsy proven rejection was 8.8% in the first 3 months and 15.5% over the 8-year follow-up. None of the pediatric CAD kidneys had ATN. Rejection episodes were restricted to the pediatric CAD kidneys alone (3/3), with no kidney rejections in the combined pediatric CAD kidney-liver transplants (0/6; P=0.003). Four ASK transplants had ATN (1 postoperative and 3 late), and all predisposed to subsequent acute rejection episodes (4/4), whereas there were no rejection episodes in ASK transplants without ATN (0/32; P<0.001). At 3 years posttransplantation, mean serum creatinines were worse in ASKs with ATN (1.5 vs. 0.9 mg/dL; P<0.001) and in all grafts with rejection episodes (1.2 vs. 0.9 mg/dL; P<0.05). UNOS RESULTS: Among the 5 age groups studied, significantly better (P<0.001) long-term graft survival rates were observed in allograft recipients in the 2 youngest age groups with ASKs without ATN: 82 +/- 3% and 81 +/- 3% for LD and 70 +/- 7% and 78 +/- 4% for CAD recipients in the 0-2.5 and 2.5- to 5-year age groups, respectively, at 6 years after transplantation. Moreover, the projected graft half-lives after the 1st year in the LD groups without ATN were at least equivalent to those of HLA-identical sibling recipients ages 19-45 years: 26.3 +/- 5 and 29.3 +/- 6 years for the 0- to 2.5- and 2.5- to 5-year age groups, respectively, and 23.3 +/- 1 years for HLA-identical transplants. The graft half-lives for CAD recipients without ATN ages 0-2.5 and 2.5-5 yearswere equivalent or better than those for LD transplants without ATN in recipients aged 19-45 years: 15.4+/- 7 and 23.7 +/- 8 years versus 15.0 +/- 0.3 years. Mean serum creatinines were superior in the 2 younger recipient age groups compared with older age groups.

CONCLUSIONS

Increased donor tissue mass of the ASK or kidney-liver transplants, in the absence of ATN, seems to confer a protective effect to infant and small child recipients of these allografts. This is manifested by a prolonged rejection-free state in the single center experience and enhanced graft survival and function in the UNOS analysis, comparable to HLA identical sibling transplants for LD infant and small child recipients and to LD adult results for CAD infant and small child recipients. To optimize this protective effect by whatever mechanism, absolute avoidance of ATN is essential in infant recipients of ASK or combined kidney-liver transplants.