Outcome of immunosuppression in children with IgA vasculitis-related nephritis.

BACKGROUND AND HYPOTHESIS: IgA vasculitis with nephritis (IgAVN) is the most common vasculitis in children. Treatment recommendations are, due to a lack of evidence, based on expert opinion resulting in variation. The aim of this study was to describe clinical presentation, treatment and outcome of an extremely large cohort of children with biopsy proven IgAVN to identify prognostic risk factors and signals of treatment efficacy. METHODS: Retrospective data were collected on 1148 children with biopsy proven IgAVN between 2005 and 2019 from 41 international paediatric nephrology centres across 25 countries and analyzed using multivariate analysis. The primary outcome was estimated glomerular filtration rate (eGFR) and persistent proteinuria at last follow up. RESULTS: The median follow up was 3.7 years (IQR 2-6.2). At last follow up, 29% of patients had an eGFR < 90 ml/min/1.73m2, 36% had proteinuria and 3% had chronic kidney disease stage 4-5. Older age, lower eGFR at onset, hypertension and histological features of tubular atrophy and segmental sclerosis were predictors of poor outcome. There was no evidence to support any specific second line immunosuppressive regimen to be superior to others, even when further analysing subgroups of children with reduced kidney function, nephrotic syndrome or hypoalbuminemia at onset. Delayed start of immunosuppressive treatment was associated with a lower eGFR at last follow up. CONCLUSION: In this large retrospective cohort, key features associated with disease outcome are highlighted. Importantly there was no evidence to support that any specific immunosuppressive treatments were superior to others. Further discovery science and well-conducted clinical trials are needed to define accurate treatment and improve outcomes of IgAVN.

Kidney biopsy adequacy and complications in children - does technique matter?

Kidney biopsy is part of the diagnostic workup of many children with renal disease. Traditionally, a perpendicular approach to the biopsy has been used, but more recently, some proceduralists have favoured a tangential approach. It is not clear if one technique is superior with regards to tissue adequacy or complication rates. In our centre, interventional radiologists (IR) use general anaesthetic and a tangential approach, whereas paediatric nephrologists (PN) use sedation and a perpendicular approach. We examined consecutive native kidney biopsies performed between January 2008 and December 2017 for adequacy (sufficient tissue for light and electron microscopy and immunofluorescence) and examined the electronic medical records for data regarding technique and complications. IR performed 72 (29%) of the 245 native kidney biopsies, obtaining more total glomeruli (median 39 vs 16, p < 0.001) and more glomeruli per tissue core (median 13 vs 8, p < 0.001) than PN. No differences in specimen adequacy were observed between the two groups (79% IR vs 81% PN, p = 0.75) and a diagnosis could be made in 99% and 94% respectively (p = 0.1). A statistically lower rate of peri-nephric haematoma (28% vs 42%, p = 0.04) was detected in the IR group, but there were no significant differences in other complications. One patient required a blood transfusion (PN) and another required surgical intervention for a perinephric haematoma (IR). CONCLUSION: IR obtained larger samples and number of glomeruli, but the overall adequacy for native kidney biopsies was good using both perpendicular and tangential techniques, with low rates of significant complications. WHAT IS KNOWN: • Kidney biopsy is integral to the diagnostic work-up of many children with kidney disease. • Kidney biopsy is a safe procedure with well-established complications in a minority of children. WHAT IS NEW: • Interventional radiologists had higher biopsy yield than paediatric nephrologists, possibly due to the tangential approach. • Biopsy adequacy rates are high using both techniques and provided a diagnosis in over 95% of cases.

Baseline characteristics of patients with atypical haemolytic uraemic syndrome (aHUS): The Australian cohort in a global aHUS registry.

AIMS: To describe the baseline characteristics and treatment of Australian patients diagnosed with atypical haemolytic uraemic syndrome (aHUS) reported to the Global aHUS Registry. METHODS: Descriptive analysis of the Australian cohort with aHUS (n = 106) was undertaken for demographics, disease characteristics and prior treatment with eculizumab; comparing with the global cohort (n = 1688) for certain pre-specified disease characteristics. RESULTS: In Australia, almost two-thirds of patients diagnosed with aHUS were female and over 80% of patients were Caucasians, with similar proportions reported in the global cohort. Less than 6% of patients in the Australia and global cohorts were reported to have a history of autoimmune disease (4% vs 2%, respectively; P = .21) or cancer (5% vs 5%, respectively; P = .93), conditions that have been associated with secondary HUS. In the Australian cohort, 26% had received a kidney transplant and 68% of patients had received eculizumab. Kidneys were the most common organ involvement, followed by gastrointestinal tract (26%) and cardiovascular system (19%), with 35% of patients reported to have had at least two organs involved within 6 months prior to baseline visit or entry into the registry. Complement factor H was the most common pathogenic complement gene variant in the Australian patients. CONCLUSION: Data from the aHUS registry confirms and defines region-specific disease characteristics among a selected group of Australian children and adults with aHUS reported to the registry. Ongoing and more inclusive data will provide further information about temporal trends and treatment outcomes, representing a unique opportunity for clinicians and researchers to further develop knowledge surrounding this rare disease.

The association between human leukocyte antigen eplet mismatches, de novo donor-specific antibodies, and the risk of acute rejection in pediatric kidney transplant recipients.

BACKGROUND: The longitudinal relationship between HLA class I and II eplet mismatches, de novo donor-specific antibodies (dnDSA) development, and acute rejection after transplantation in childhood is unknown. METHODS: Eplet mismatches at HLA class I and II loci were calculated retrospectively for each donor/recipient pair transplanted between 2005 and 2015 at a single Australian center. Logistic regression analyses were conducted to determine the association between the number of eplet mismatches, dnDSA, and acute rejection. RESULTS: The cohort comprised 59 children (aged 0-18 years) who received their first kidney allograft and were followed for median (interquartile range) 4.5 (± 2.6) years. Overall, 32% (19/59) developed dnDSA (class I 3% (2/59), class II 14% (8/59), 15% class I and II (9/59)), and 24% (14/59) developed biopsy-proven acute rejection. Every unit increase in class I and II eplet mismatches corresponded to an increase in risk of class I (odds ratio (OR) 1.22, 95% CI 1.07-1.39, p < 0.01) and class II (OR 1.06, 95% CI 1.01-1.11, p = 0.02) dnDSA development. Compared with recipients without dnDSA, class I and II dnDSA were associated with direction of effect towards increased risk of acute cellular rejection (class I: OR 5.87, 95% CI 0.99-34.94, p = 0.05; class II: OR 12.00, 95% CI 1.25-115.36, p = 0.03) and acute antibody-mediated rejection (class I: OR 25.67, 95% CI 3.54-186.10, p < 0.01; class II: OR 9.71, 95% CI 1.64-57.72, p = 0.01). CONCLUSIONS: Increasing numbers of HLA class I or II eplet mismatches were associated with the development of dnDSA. Children who developed dnDSA were also more likely to develop acute rejection compared with children without dnDSA.

Post-renal transplant urolithiasis in children: an increasingly diagnosed complication: a retrospective cohort study.

OBJECTIVE: Urolithiasis in renal transplant (RTx) recipients is a potential cause of allograft loss if obstruction is untreated. It is not clear if paediatric transplant recipients are following the global trend for increased prevalence of urolithiasis over time. DESIGN/SETTING/PATIENTS: A retrospective chart review was undertaken to evaluate the frequency, risk factors and characteristics of post-RTx urolithiasis over two decades (1995-2016), in a tertiary Australian paediatric hospital. RESULTS: Stones were diagnosed in 8 of 142 (5.6%) recipients, 6 of whom were transplanted in the latter decade. All patients were male, with a median age 4.9 years and median weight 11.8 kg. Presentation was with haematuria (n=4), pain (n=2), dysuria (n=2), stone passage (n=1) and asymptomatic (n=1). Time to presentation was bimodal; three stones were identified in the initial 3 months post RTx and the remainder after 31-53 months. Two stones were in association with retained suture material and two patients had recurrent urinary tract infections. The average stone size was 8.4 mm. Five stones were analysed; all contained calcium oxalate, three were mixed, including one with uric acid. Five (83.3%) children had hypercalciuria but none had hypercalcaemia. Cystolithotripsy was the the most common treatment (n=5), in combination with citrate supplementation. No graft was lost due to stones. CONCLUSIONS: Calculi occur with increasing frequency after renal transplantation. Clinicians need a high index of suspicion as symptoms may be atypical in this population. The cause for the increased frequency of stones in transplant recipients is not clear but is in keeping with the increase seen in the general paediatric population.

Intra-abdominal Complications After Pediatric Kidney Transplantation: Incidence and Risk Factors.

BACKGROUND: The incidence and types of intra-abdominal complications after pediatric transplantation are not well established, and specific risk groups have not been clearly identified. METHODS: A retrospective chart review of all pediatric transplant recipients between 1995 and 2016 was undertaken. Intra-abdominal complications were grouped into 4 categories: fluid collections, gastrointestinal, vascular, and urogenital. Donor, recipient, and transplant characteristics were evaluated using univariate and multivariate logistic regressions. RESULTS: There were 146 transplants meeting the inclusion criteria. The mean follow-up time was 4.6 ± 3.7 years (range, 0.3-18 y). The mean weight at transplantation was 31.5 ± 16.5 kg (range, 9-78), with 24 (16%) recipients being <15 kg and 23% younger than 5 years. Thirty-four (23%) patients had previous abdominal surgery. There were 32 complications identified in 27 (18%) transplant recipients. Fluid collections requiring surgical drainage developed in 9 (6.2%), gastrointestinal surgical complications in 12 (8.2%), vascular complications in 5 (3.5%), and urogenital complications in 6 (4.1%). There were only 3 graft losses due to abdominal complications, all after renal vein thrombosis. Weight <15 kg at the time of transplant (P = 0.016), previous abdominal surgery (P = 0.047), and intraperitoneal surgical technique (P = 0.008) were risk factors in the univariate analysis using Cox regression models, whereas only weight <15 kg (P = 0.003) and previous abdominal surgery (P = 0.008) were retained in the multivariate analysis. CONCLUSIONS: Intraabdominal complications occur in almost 1 in 5 pediatric renal transplant recipients. Weight <15 kg and previous abdominal surgery are risk factors for developing such complications.

DEC205-DC targeted DNA vaccine against CX3CR1 protects against atherogenesis in mice.

Studies disrupting the chemokine pathway CX3CL1 (fractalkine)/ CX3CR1 have shown decreased atherosclerosis in animal models but the techniques used to interrupt the pathway have not been easily translatable into human trials. DNA vaccination potentially overcomes the translational difficulties. We evaluated the effect of a DNA vaccine, targeted to CX3CR1, on atherosclerosis in a murine model and examined possible mechanisms of action. DNA vaccination against CX3CR1, enhanced by dendritic cell targeting using DEC-205 single chain variable region fragment (scFv), was performed in 8 week old ApoE-/- mice, fed a normal chow diet. High levels of anti-CX3CR1 antibodies were induced in vaccinated mice. There were no apparent adverse reactions to the vaccine. Arterial vessels of 34 week old mice were examined histologically for atherosclerotic plaque size, macrophage infiltration, smooth muscle cell infiltration and lipid deposition. Vaccinated mice had significantly reduced atherosclerotic plaque in the brachiocephalic artery. There was less macrophage infiltration but no significant change to the macrophage phenotype in the plaques. There was less lipid deposition in the lesions, but there was no effect on smooth muscle cell migration. Targeted DNA vaccination to CX3CR1 was well tolerated, induced a strong immune response and resulted in attenuated atherosclerotic lesions with reduced macrophage infiltration. DNA vaccination against chemokine pathways potentially offers a potential therapeutic option for the treatment of atherosclerosis.

Consensus opinion on diagnosis and management of thrombotic microangiopathy in Australia and New Zealand.

Thrombotic microangiopathy (TMA) arises in a variety of clinical circumstances with the potential to cause significant dysfunction of the kidneys, brain, gastrointestinal tract and heart. TMA should be considered in all patients with thrombocytopenia and anaemia, with an immediate request to the haematology laboratory to look for red cell fragments on a blood film. Although TMA of any aetiology generally demands prompt treatment, this is especially so in thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS), where organ failure may be precipitous, irreversible and fatal. In all adults, urgent, empirical plasma exchange (PE) should be started within 4-8 h of presentation for a possible diagnosis of TTP, pending a result for ADAMTS13 (a disintegrin and metalloprotease thrombospondin, number 13) activity. A sodium citrate plasma sample should be collected for ADAMTS13 testing prior to any plasma therapy. In children, Shiga toxin-associated haemolytic uraemic syndrome due to infection with Escherichia coli (STEC-HUS) is the commonest cause of TMA, and is managed supportively. If TTP and STEC-HUS have been excluded, a diagnosis of aHUS should be considered, for which treatment is with the monoclonal complement C5 inhibitor, eculizumab. Although early confirmation of aHUS is often not possible, except in the minority of patients in whom auto-antibodies against factor H are identified, genetic testing ultimately reveals a complement-related mutation in a significant proportion of aHUS cases. The presence of other TMA-associated conditions (e.g. infection, pregnancy/postpartum and malignant hypertension) does not exclude TTP or aHUS as the underlying cause of TMA.

Consensus opinion on diagnosis and management of thrombotic microangiopathy in Australia and New Zealand.

Thrombotic microangiopathy (TMA) arises in a variety of clinical circumstances with the potential to cause significant dysfunction of the kidneys, brain, gastrointestinal tract and heart. TMA should be considered in all patients with thrombocytopenia and anaemia, with an immediate request to the haematology laboratory to look for red cell fragments on a blood film. While TMA of any aetiology generally demands prompt treatment, this is especially so in thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS), where organ failure may be precipitous, irreversible and fatal. In all adults, urgent, empirical plasma exchange (PE) should be started within 4-8 h of presentation for a possible diagnosis of TTP, pending a result for ADAMTS13 activity (a disintegrin and metalloprotease thrombospondin, number 13). A sodium citrate plasma sample should be collected for ADAMTS13 testing prior to any plasma therapy. In children, Shiga toxin-associated haemolytic uraemic syndrome due to infection with Escherichia coli (STEC-HUS) is the commonest cause of TMA, and is managed supportively. If TTP and STEC-HUS have been excluded, a diagnosis of aHUS should be considered, for which treatment is with the monoclonal complement C5 inhibitor, eculizumab. While early confirmation of aHUS is often not possible, except in the minority of patients in whom autoantibodies against factor H are identified, genetic testing ultimately reveals a complement-related mutation in a significant proportion of aHUS cases. The presence of other TMA-associated conditions (e.g. infection, pregnancy/postpartum and malignant hypertension) does not exclude TTP or aHUS as the underlying cause of TMA.

Desensitisation strategies in high-risk children before kidney transplantation.

BACKGROUND: Transplantation is the preferred modality for renal replacement therapy in children. With increasing rates of re-transplantation within the paediatric population, there are more sensitised children on waiting lists. One issue with developing strategies to treat these children is the number of different definitions of sensitisation. and we would therefore recommend an immunological risk stratification approach. METHODS: We discuss methods of sensitisation prevention, assessment and management, including paired exchange programmes and desensitisation protocols. RESULTS: There are limited published evidence-based data for desensitisation in adults and none in children; thus, we present information on the available therapies currently in use. DISCUSSION: Further research is required to investigate strategies which prevent sensitisation in children, including the healthcare utility of incorporating epitope-based matching into organ allocation algorithms. Controlled studies are also needed to establish the most appropriate desensitisation regimen(s).

Daedalic DNA vaccination against self antigens as a treatment for chronic kidney disease.

Chronic kidney disease (CKD) is a major cause of death and morbidity in Australia and worldwide. DNA vaccination has been used for targeting foreign antigens to induce immune responses and prevent autoimmune disease, viral infection and cancer. However, the use of DNA vaccination has been restricted by a limited ability to induce strong immune responses, especially against self-antigens which are limited by mechanisms of self-tolerance. Furthermore, there have been few studies on the potential of DNA vaccination in chronic inflammatory diseases, including CKD. We have established strategies of DNA vaccination targeting specific self-antigens in the immune system including co-stimulatory pathways, T cell receptors and chemokine molecules, which have been effective in protecting against the development of CKD in a variety of animal models. In particular, we find that the efficacy of DNA vaccination is improved by dendritic cell (DC) targeting and can protect against animal models of autoimmune nephritis mimicking human membranous nephropathy. In this review, we summarize several approaches that have been tested to improve the efficacy of DNA vaccination in CKD models, including enhanced DNA vaccine delivery methods, DNA vaccine modifications and new molecular targets for DNA vaccination. Finally, we discuss the specific application of DNA vaccination for preventing and treating CKD.

Is laparoscopic donation safe for paediatric recipients?--a study of 85 paediatric recipients comparing open and laparoscopic donor nephrectomy.

INTRODUCTION: The safety of adult laparoscopic donor nephrectomy remains controversial with respect to paediatric recipients with few data existing about its efficacy. Small studies have shown no difference in graft survival when compared with open techniques, but previous data from United Network for Organ Sharing suggests a higher incidence of rejection in laparoscopically procured kidneys. METHODS: We examined the outcome in a total of 85 consecutive paediatric renal recipients, comparing 46 recipients of laparoscopically procured kidneys (performed over a 3-year period, 2004-07) to a historical control of 39 open donor recipients. Thirty-seven laparoscopic donors were by the hand-assisted technique. RESULTS: Mean recipient age was 9.8 (SD 5.04) years in the laparoscopic group and 10.4 (SD 4.67) years in the open group (P = 0.617). Two patients had delayed graft function in the laparoscopic group (4.3%) and one (2.5%) in the open group (P = 0.562). At 1 year follow-up, there was 100% graft survival in the laparoscopic group compared to 92% (P = 0.093) in the open group. Incidence of biopsy-proven acute rejection within 1 year of transplant was 26% (16 episodes in 12 patients) in the laparoscopic group compared to 41% (29 episodes in 16 patients) in the open group (P = 0.219). There were no deaths in the laparoscopic group but there were three deaths (7.6%) in the open group (P = 0.093). CONCLUSIONS: Our experience of laparoscopic kidney donation for paediatric recipients suggests excellent outcome with no difference in rejection rate or graft survival compared to open donation. Laparoscopic donation is the optimal method of kidney procurement for paediatric recipients.

Thromboxane prostanoid receptor stimulation induces shedding of the transmembrane chemokine CX3CL1 yet enhances CX3CL1-dependent leukocyte adhesion.

In atherosclerosis, chemokines recruit circulating mononuclear leukocytes to the vascular wall. A key factor is CX(3)CL1, a chemokine with soluble and transmembrane species that acts as both a chemoattractant and an adhesion molecule. Thromboxane A(2) and its receptor, TP, are also critical to atherogenesis by promoting vascular inflammation and consequent leukocyte recruitment. We examined the effects of TP stimulation on processing and function of CX(3)CL1, using CX(3)CL1-expressing human ECV-304 cells and primary human vascular endothelial cells. TP agonists promoted rapid shedding of cell surface CX(3)CL1, which was inhibited by pharmacological inhibitors or specific small interfering RNA targeting tumor necrosis factor-alpha-converting enzyme (TACE). Because it reduced cell surface CX(3)CL1, we predicted that TP stimulation would inhibit adhesion of leukocytes expressing the CX(3)CL1 cognate receptor but, paradoxically, saw enhanced adhesion. We questioned whether the enhanced ability of the remaining membrane-associated CX(3)CL1 to bind targets was caused by changes in its lateral mobility. Using fluorescence recovery after photobleaching, we found that plasmalemmal CX(3)CL1 was initially tethered but ultimately mobilized by TP agonists. TP stimulation provoked clustering of transmembrane CX(3)CL1 at sites of contact with adherent leukocytes. These data demonstrate that TP stimulation induces two distinct effects: a rapid cleavage of surface CX(3)CL1, thereby releasing the soluble chemoattractant, plus mobilization of the remaining transmembrane CX(3)CL1 to enhance the avidity of interactions with adherent leukocytes. The dual effect of TP allows CX(3)CL1 to recruit leukocytes to sites of vascular inflammation while enhancing their adhesion once recruited.

Generalized arterial calcification of infancy: phenotypic spectrum among three siblings including one case without obvious arterial calcifications.

Generalized arterial calcification of infancy (GACI) (OMIM no. 208000) is characterized by calcification of the major arteries and soft tissues and associated with mutations in the ENPP1 gene. Most affected patients die within the first 6 months of life although prolonged survival is increasingly recognized. We report on three siblings with GACI and striking phenotypic variability. Two siblings (including the sibling survivor) were compound heterozygotes for mutations in exon 7 (c.783C>G (p.Y261X)) and exon 8 (c. 878_879delAA (p.K293fsX5)) of the ENPP1 gene confirming the diagnosis of GACI. The sibling survivor did not have calcification on X-ray studies or evidence of hypophosphatemic rickets. GACI may be under recognized and we emphasize consideration of this condition in patients with multiple arterial stenosis even in the absence of radiographic calcification. This adds to the expanding phenotype of GACI and supports a potential role for modifying genes.

Expression and targeting of CX3CL1 (fractalkine) in renal tubular epithelial cells.

The chemokine CX3CL1 plays a key role in glomerulonephritis and can act as both chemoattractant and adhesion molecule. CX3CL1 also is upregulated in tubulointerstitial injury, but little is known about the subcellular distribution and function of CX3CL1 in renal tubular epithelial cells (RTEC). Unexpectedly, it was found that CX3CL1 is expressed predominantly on the apical surface of tubular epithelium in human renal transplant biopsy specimens with acute rejection or acute tubular necrosis. For studying the targeting of CX3CL1 in polarized RTEC, MDCK cells that expressed untagged or green fluorescent protein-tagged CX3CL1 were generated. The chemokine was present on the apical membrane and in subapical vesicles. Apical targeting of CX3CL1 was not due to signals that were conferred by its intracellular domain, to associations with lipid rafts, or to O-glycosylation but, rather, depended on N-linked glycosylation of the protein. With the use of fluorescence recovery after photobleaching, it was found that CX3CL1 is immobile in the apical membrane. However, CX3CL1 partitioned with the triton-soluble rather than -insoluble cellular fraction, indicating that it is not associated directly with the actin cytoskeleton or with lipid rafts. Accordingly, disruption of rafts through cholesterol depletion did not render CX3CL1 mobile. For exploration of potential functions of apical CX3CL1, binding of CX3CR1-expressing leukocytes to polarized RTEC was examined. Leukocyte adhesion to the luminal surface was enhanced significantly when CX3CL1 was present. These data demonstrate that CX3CL1 is expressed preferentially on the apical membrane of RTEC and suggest a novel function for the chemokine in recruitment and retention of leukocytes in tubulointerstitial inflammation.

The use of darbepoetin in infants with chronic renal impairment.

Darbepoetin is a newer analogue of epoetin, with a longer half-life, that allows less frequent administration. There are currently no published data available for its use in infants. We report our experience with this drug in infants with chronic renal impairment, weighing less than 8 kg. Infants had baseline haemoglobin (Hb), iron, ferritin and transferrin levels measured. They were started on approximately 0.5 microg/kg per week of darbepoetin. Hb levels were checked every 2-4 weeks, and iron studies were performed every 4 weeks. Iron supplementation was prescribed to maintain ferritin levels>100 microg/l and transferrin saturation levels>20%. Follow up was for 20 weeks. Six infants with a mean weight of 4.08 kg and a mean creatinine of 259 micromol/l were included. Three infants were medically stable throughout the study, and the mean darbepoetin dose was decreased to 0.25 microg/kg per week. Their dosing interval was increased to every 3-4 weeks. The other three infants were less stable and had multiple medical problems, including periods of haemodialysis and surgery. These infants failed to reach target Hb level, despite an increase in the mean dose of darbepoetin to 1.2 microg/kg per week. In conclusion, darbepoetin can be successfully administered to infants with chronic renal insufficiency, but the dose needs to be tailored to each individual. Administration would be facilitated by smaller unidose syringes.

Renal transplant biopsy specimen adequacy in a paediatric population.

Updated guidelines on the diagnosis of acute allograft rejection including criteria for biopsy specimen adequacy were published in 1999. We sought to determine the adequacy of specimens in paediatric transplant patients and identify factors influencing adequacy. All renal transplant biopsies performed between 1998 and 2003 were classified as adequate (n =25), minimal (n =19) or inadequate (n =27) in accordance with the Banff 97 criteria, and the histological diagnoses were documented. The effect on specimen adequacy of grade of operator, method of sedation, age of child, needle gauge, number of cores and total core length was then investigated. Overall, a minimal or adequate specimen was obtained in 62% of cases. No histological diagnosis could be made in 30% of all specimens, just over half of which were inadequate. Higher rates of rejection were found in adequate (52%) than inadequate (33%) samples. The grade of operator (p =0.498), the age of the child at the time of biopsy (p =0.815) and type of sedation (p =0.188) did not affect adequacy. More than one core was obtained in 38 (54%) cases, and this was significantly associated with specimen adequacy (p <0.0005) as was longer total core length (p =0.002). Clinical features in isolation are not sufficient for the diagnosis of acute allograft rejection. Renal biopsy remains the gold standard and relies on adequate specimen collection. Our data shows that specimen adequacy according to the Banff 97 guidelines is achievable in children and that more than one core at the time of sampling significantly improves this achievement. Adequate sampling reduces the risk of an inconclusive histological diagnosis.