Background and Aims In the pediatric population, transplantation remains the first-line therapy in patients with end-stage renal disease (ESRD). However, it is not always possible, increasing the need for other kidney replacement therapy (KRT) modalities, and hemodialysis (HD) has been growing as a modality choice in recent years. To provide quality HD treatment, efficient vascular access is mandatory, and the arteriovenous fistula (AVF) is advocated as the best long-term access option. However, its creation is technically challenging, and its development and maintenance are some of the most difficult elements in the pediatric population. In this study, we describe our experience in the utilization of AVFs in children and adolescents on HD. Method We conducted a retrospective study including all the AVFs performed in our center on underage patients between January 2006 and December 2022. We reviewed the medical records, collected data on demographic variables, AVF characteristics, blood test results, and clinical outcomes. Statistical analysis was performed using SPSS software. Results Forty-three AVFs were performed in 32 pediatric patients. The median age at first AVF construction was 13.5 years (min 4.8; max 17.9). The most frequent etiology of ESRD was congenital anomalies of kidney and urinary tract (n = 20, 62.5%) and most patients (n = 24, 75.0%) were already receiving KRT. Median follow-up time was 16.4 months (min 1; max 98.4) and, at the end of the follow-up period, most patients (n = 22, 68.8%) were transplanted. The mortality rate was 6.3% (n = 2). In what concerns to the location of the AVF, radiocephalic was the first choice in 46.9% of the cases (n = 15), accounting for 34.9% of the total AVFs. Brachiocephalic location was used in 34.4% (n = 11) of first fistulas and 6 subsequent accesses, accounting for 39.5% of the total AVFs. The brachiobasilic location was chosen in 18.8% (n = 6) of the first AVFs and 25.6% of the total AVFs. Primary AVF failure occurred in 26.6% (n = 11) cases and, in 4 of these (36.4%), it was possible to successfully use the same location for a second AVF. We observed no statistical association between primary AVF failure dysfunction and gender, age at the construction of the first fistula, AVF location, or dialysis vintage. Platelet-lymphocyte (PLR) and neutrophil-lymphocyte (NLR) ratios also did not differ between groups. Primary and secondary patency rates at one year were, respectively, 62.5% and 93.8%. With respect to total AVF complications, we observed: thrombosis (27.9%), stenosis (18.6%), distal ischemia induced by vascular access (4.7%), and high flow/aneurismatic dilations (18.6%). The presence of complications was statistically related to age (p = 0.046), with more events in older patients at the time of AVF construction. There was no statistical difference between complications’ occurrence and AVF type, sex, gender, PLR, and NLR. Conclusion The utilization of AVF for HD has been growingly recognized as a safe and efficient alternative for the performance of KRT in pediatric patients. Although larger studies are needed, we demonstrate positive results in its usage in a pediatric population, with high primary and secondary patency rates. These outcomes were independent of the AVF location. We also advocate AVF usage in younger patients, as complications were associated with older age. PLR and NLR, which are emerging biomarkers for systemic inflammation, were not associated with AVF dysfunction, aligning with the results of other studies in pediatrics.

Background and Aims Hepatocyte nuclear factor 1β (HNF1β)-associated disorder is a rare entity that may present with a wide range of clinical phenotypes. Genetic transmission is autosomal dominant, penetrance is incomplete, and expression is variable, which can contribute to different clinical presentations, raising difficulties to reach the diagnosis. The most common findings are renal cysts, responsible for kidney function decline, as well as diabetes mellitus, among other possible organs’ manifestations such as the pancreas, liver, brain and parathyroid gland. The disease arises through monoallelic single nucleotide deleterious variants (SNVs) or whole-gene deletions, in the chromosome 17q12. Method Retrospective analysis of patients with HNF1β-associated disease followed in pediatric nephrology unit, throughout the last 10 years (2013-2022), in our pediatric tertiary center. Data regarding demographic variables, along with family history, relevant clinical information and genetic variants were collected from electronical clinical files. Results A total of 6 patients were followed in our centre, mostly males (n = 5). Regarding age at diagnosis, two patients were diagnosed prenatally, owing to positive familial history and renal cysts, while for the other 4 patients (de novo mutations) the age at diagnosis ranged from one to 13 years-old (yo). Five patients presented with renal cysts, while the other patient presented with unilateral urinary tract dilation. Only one patient presented with diabetes mellitus. Regarding other possible comorbidities, two patients presented with neurodevelopmental disorders and one with hypertension. At presentation, 3 patients had chronic kidney disease stage 3. The mean decrease in glomerular filtration rate was 1.44 ml/min/year (according to Schwartz “bedside” formula). Creatinine levels almost doubled in 3 of the patients since referral (adolescents currently with 1.5-2 mg/dL), while remaining in the normal range in the other patients. Two patients presented with low grade proteinuria during follow-up (max protein/creatinine ratio 0.36 g/g). Values of calcium, transaminases and uric acid were normal in all patients. Familial history of kidney disease, namely cysts or chronic kidney disease, was positive in 3 patients. In terms of genetic transmission, 3 patients had SNVs, while the other 3 presented with larger deletions in chromosome 17q12. Conclusion In conclusion, in these patients, a high degree of suspicion is needed for diagnosis, owing to the rarity of the disease and heterogeneity of its manifestations. A multidisciplinary approach and genetic counseling are determinant for disease management. Families of the affected individuals should be tested, even if asymptomatic, to determine if the HNF1β variant was inherited or occurred de novo. Given the small number of patients, it would be important to widen the sample through a multicentric study.

Background and Aims Minimal change disease (MCD) is the main cause of nephrotic syndrome in pediatric age and it is responsible for 10-25% of the cases in adults. It is characterized by minimal glomerular abnormalities in light microscopy, usually without immunoglobulins or complement deposits in immunofluorescence (IF). There is a subgroup of patients that presents with IgM deposition in IF, which has been described as a more aggressive disease, with frequent relapses [1], dependence of steroids [2] and worse outcomes. Method This is a retrospective study that analyses the follow up of 50 adult MCD patients in the nephrology consult, with diagnosis in childhood or adulthood. They had renal biopsies performed between 2009 and 2022. We did not include inappropriate biopsy samples, biopsies without IF or positive for C1q. We compared the characteristics between IgM positive (IgM+) and IgM negative (IgM-) patients at diagnosis, as well as the number of relapses per year, age of presentation and association with steroid-dependence or steroid-resistance. Results There were 23 (46%) patients in the IgM+ group and 27 (54%) in the IgM- group, with a mean follow-up of 10.2± 7.8 years. The IgM- subgroup was older at biopsy time (52 (30-74) years vs IgM+ 15 (13-23) years; p = 0.001) and this is probably related with the age of disease presentation, which was younger in the IgM+ group (12 (5-16) years vs IgM- 52 (73-13) years; p = 0.001). The groups were similar in sex distribution (IgM+ male n = 15 (55.6%) vs IgM- male n = 10 (44.0%); p = 0.395). There were no differences in diabetes and dyslipidemia frequencies between the two groups (Diabetes: IgM+ n = 1 (4.3%), IgM- n = 3 (11.3%), p = 0.614; Dyslipidemia: IgM+ n = 7 (30.4%), IgM- n = 7 (25.9%), p = 0.723), but the IgM- group had more patients with hypertension (IgM+ n = 2 (8.7%), IgM- n = 9 (33%), p = 0.046). The estimated glomerular filtration rate based on creatinine (eGFRcr) at biopsy time was higher in the IgM+ group (124 (104-130) ml/min/1.73 m2 vs IgM- with 96 (84-111) ml/min/1.73 m2; p = 0.003), but this happens probably due to the age as a confounding variable. In regard to the number of relapses per year, the IgM+ group had significantly more relapses than the IgM- group (IgM+ with 0.61 (0.27-1.00) relapses per year; IgM- with 0.17 (0.01-0.65) relapses per year; p = 0.011). The steroid-dependence (IgM+ n = 15 (65%); IgM- n = 11 (47%); p = 0.084) and the steroid-resistance (IgM+ n = 6 (26%); IgM- n = 3 (11%); p = 0.270) isolated outcomes were not significantly different in the two groups, but when we analyze the composed outcome of steroid-dependence plus steroid-resistance we have worse outcomes in the IgM+ subgroup (IgM+ n = 21 (91.3%); IgM- n = 14 (51.8%); p = 0.04; ORR 9.72; IC 95% 2.37-33.33). An IgM+ patient has 9.7 times the odd of being steroid-dependent or steroid-resistant of an IgM- patient. From our 50 patients, 3 evolved to stage 5 chronic kidney disease with dialysis dependency, being all of those patients IgM+. One of those patients had a recurrency of MCD after kidney transplant. There were 3 deaths with non-related to kidney disease causes, 1 in the IgM+ and 2 in the IgM- groups. Genetic test was performed in 5 of the IgM+ patients, with 4 positive results for mutations. Only 2 IgM- patients did genetic test, all without mutation´s identification. Conclusion This study supports the evidence that MCD patients with IgM+ biopsies have younger age MCD's presentation, more relapses per year and more steroid dependence plus resistance. Dialysis was started in 3 IgM+ patients and this group seems to have higher frequency of genetic mutations. This suggests that genetic testing could be important for future prognosis prediction and treatment options in the IgM+ patients, but further studies with a bigger study population need to be done to establish this relation.

BACKGROUND AND AIMS Kidney transplantation (KT) improves survival and quality of life of patients with end-stage renal disease. However, there is still an unbalance between supply and demand for kidneys. To increase the number of available grafts and reduce the waiting list for transplantation, recruitment of older living donors has expanded. This approach remains controversial for several reasons, including the impact of kidney function decline on long-term graft and recipient survival. We aimed to evaluate the impact of living donor (LD) age on recipient graft survival and on graft function decline over time. METHOD This is a Unicenter retrospective observational study that included kidney transplants of LD between 2008 and 2017. Several clinical data were analyzed, including donors’ comorbidities, immunological features of the transplant, induction immunosuppression, number of acute rejections (AR) at the first year, and the graft glomerular filtration rate (eGFR) during the follow-up period. The eGFR was calculated using the CKD-EPI equation. The LDs were classified as young (<60 years) and old (≥60 years) for analysis purposes. The Kaplan–Meier curves and Cox proportional hazards multivariable regression were used for survival analysis and linear mixed regression was used to evaluate the annual slope of recipient eGFR, comparing both groups. RESULTS We observed 210 LD kidney transplants: 86% (n = 181) from young (D < 60) and 14% (n = 29) from old donors (D ≥60). The average age was 41.3 ± 13.3 years for recipients and 48.0 ± 10.6 years for donors. The pre-donation eGFR was significantly higher in D < 60 than D ≥60 (101.7 ± 14.0 versus 90.2 ± 11.0 mL/min/1.73 m2; P  < 0.001). There was no significant difference in AR in the first year between both groups. (Table 1) The censored recipient graft survival was similar for D < 60 and D ≥60 (86% versus 84%, P = 0.144) (Figure 1) and the older donors’ age was not a predictor of censored graft failure [hazard ratio (HR): 2.689 (95% CI: 0.832–8.690; P = 0.098)]. Although not statistically significant, the overall recipient graft survival was lower in D ≥60 (67% versus 86%, P = 0.071) (Figure 1) and donors’ age ≥60 years was an independent predictor of global recipient graft failure (HR: 3.303, 95% CI: 1.102–9.899; P = 0.033). Linear mixed regression showed that recipient eGFR from D ≥60 was lower than D < 60 at 12 months [46.5 mL/min/1.73 m2 (95% CI: 41.4–51.5) versus 58.6 mL/min/1.73 m2 (95% CI: 56.4–60.8); P = 0.026] and, beyond 1-year, eGFR slope annual decline was steeper in older donor recipients by −1.4 mL/min/1.73 m2 each year [95% CI: (−2.4) to (−0.4); P = 0.005] than in those from younger donors. CONCLUSION Although the greater eGFR graft decline in the first 12 months and beyond, we demonstrated that kidneys from older living donors did not significantly compromise the censored recipient graft survival. We did not evaluate the age match between donor and recipient, as has been done in other studies, but even so, these results support the importance of increasingly encouraging KT from older living donors. It can improve the quality of life, compared to the time on dialysis and, especially for old candidates, can be the only chance to get transplanted.

Background and Aims There is a high-risk of progressive chronic kidney disease (CKD) in patients with neurogenic bladder (NB) and early detection of estimated glomerular filtration rate (eGFR) reduction is essential, preventing delayed diagnosis. Creatinine-based formulas can overestimate eGFR in these patients due to decreased muscle mass. This study aims to compare eGFR calculated by different equations using serum creatinine (Cr) and/or cystatin C (CysC), in children with NB, and analyse the influence of demographic variables and proteinuria. Methods Data on pediatric patients with NB and CKD stage 1 and 2, based on eGFR calculated by the CKiD-Cr formula, were collected from January 2009 to December 2022, in a Pediatric Nephrology Unit from a tertiary hospital. The eGFR was calculated using CKiD CysC, Schwartz combined Cr/CysC, Zapitelli-CysC and Zapitelli combined Cr/CysC formulas. Proteinuria was defined by urine protein-to-creatinine ratio greater than 0.2 (mg/mg). Results Fifty patients were evaluated, with a median (25th-75th percentile) age of 14.2 (9.0-16.7) years, 48% (n = 24) female, with a median height of 142 (119.8-154.3) cm, mostly below to 5th percentile (64%, n = 32) and a median body mass index of 20.5 (15.5-26.7) kg/m2, 58% (n = 29) of patients had lipo/myelomeningocele and 76% (n = 38) were classified as stage 1 CKD. The median eGFR (ml/min/1.73m2) calculated by different formulas was: CKiD-Cr 108.1 (89.2-129.6); CKiD-CysC 77.1 (59.7-87.7), CKiD- Cr/CysC 86.6 (67.4-98.1); Zapitelli-CysC 83.3 (63.3-95.7) and Zapitelli combined- Cr/CysC 101.4 (75.5-121.2). When compared to CKiD-Cr, all the CysC-based formulas showed significantly lower values of eGFR (p<0.01). No statistical differences were obtained in eGFR calculated by CKiD-Cr and CKiD-CysC equations regarding age, sex, percentile of height or body mass index. In patients without independent gait (wheelchair or orthosis), with more muscle atrophy and underdeveloped lower limbs (54%, n = 27), the eGFR calculated by CKiD- Cr equation was higher than in the patients who are ambulatory (119.0 (102.8-150.0) vs 91.6 (64.5-111.8); p<0.01). On the other hand, there were no differences regarding eGFR obtained by CKiD-CysC in those two groups of patients (p = 0.640). Proteinuria was detected in 39% (n = 15) of the patients with stage 1 CKD and of these 87% (n = 13) had CKD upstaging using CKiD-CysC equation. In addition, the difference between the median Cr-eGFR and CysC-eGFR was significantly higher in the group of patients with proteinuria (53.0 (36.2-59.7) vs 32.6 (13.4-45.9); p = 0.007). Proteinuria was significantly higher in the group of children with more muscle atrophy, without independent gait (wheelchair or orthosis) compared to ambulatory (0.30 (0.12-0.43) vs 0.12 (0.06-0.20); p = 0.021). Conclusions In pediatric patients with NB and poor muscle mass Cr-based formulas can overestimate eGFR and delay the diagnosis and correct staging of CKD. In these patients CysC-based equations seem to be more reliable in assessing kidney function. In children with NB proteinuria appears to be a possible early and sensitive marker of CKD progression, mostly in those with more muscle depletion.