An innovative diagnostic procedure in children: videourodynamics with contrast-enhanced voiding urosonography.

Contemporary videourodynamic (VUD) investigation combines voiding cystourethrography (VCUG) and urodynamics into one study, which allows simultaneous visualization of the urinary tract by ionizing radiation alongside the measurement of sensation, capacity, compliance, and detrusor pressure during bladder filling and voiding using one double lumen catheter. Today VUD is a benchmark for evaluating the lower urinary tract disorders in children because it evaluates urinary bladder and sphincter function and visualizes bladder morphology and vesicoureteral reflux (VUR) presence at the same time. Several previous studies of fluoroscopic videourodynamics issued concerns regarding radiation exposure. This technical report aims to describe a new modality of VUD in children by replacing fluoroscopic VCUG with contrast-enhanced voiding urosonography (ceVUS). ceVUS using second-generation contrast media and harmonic imaging is a radiation-free and highly sensitive imaging modality used to detect VUR in children. We simultaneously performed an infusion of ultrasound contrast through the double lumen urodynamic catheter during urodynamic evaluation. This article describes the advantages of this method compared with a conventional technique. In addition to being radiation-free, this procedure of advanced videourodynamics method can better detect vesicoureteral reflux and intrarenal reflux combined with urodynamic disorders associated with VUR.

Clinical and histopathological characteristics of COL4A3 c.2881+1G>A variant causing Alport spectrum disorders in Croatian population.

Alport syndrome (AS) and thin basement membrane nephropathy (TBMN) are part of the spectrum of kidney disorders caused by pathogenic variants in α3, α4, or α5 chains of the collagen type IV, the major structural component of the glomerular basement membrane (GBM). Using targeted next-generation sequencing (NGS), 34 AS/TBMN patients (58.8% male) from 12 unrelated families were found positive for heterozygous c.2881+1G>A variant of the COL4A3gene, that is considered disease-causing. All patients were from the continental or island part of Croatia. Clinical, laboratory, and histopathological data collected from the medical records were analyzed and compared to understand the clinical course and prognosis of the affected patients. At the time of biopsy or first clinical evaluation, the mean age was 31 years (median: 35 years; range: 1 - 72 years). Hematuria was present in 33 patients (97.1%) and 19 (55.9%) patients had proteinuria. There were 6 (17.6%) patients with hearing loss, 4 (11.8%) with ocular lesions, and 11 (32.4%) with hypertension. Twenty-three (67.6%) patients had proteinuria at follow-up, and 5 (14.7%) patients with the median age of 48 years (range: 27-55) progressed to kidney failure, started dialysis, or underwent kidney transplantation. Of the 13 patients who underwent kidney biopsy, 4 (30.8%) developed focal segmental glomerulosclerosis (FSGS), and 8 (66.7%) showed lamellation of the GBM, including all patients with FSGS. It is essential to conduct a detailed analysis of each collagen type IV genetic variant to optimize the prognosis and therapeutic approach for affected patients.

Differentinating between non-transfusion dependant ß-thalassemia and iron deficinecy anemia in children using ROC and logistic regression analysis: two novel discrimination indices designed for pediatric patients.

Introduction: This cross-sectional study enrolled a group of 271 children with microcytic anemia in order to test the performance of 41 single and 2 composite formulas andindices in distinguishing between ß-thalassemia (ß-thal) and iron deficiency anemia (IDA) in the pediatric population. Methods: Optimal pediatric cut-off values from the previously published formulas and indices were generated using ROC analysis. Logistic regression in R using generalized linear models (GLM) generated two new indices. Results: Formulas and indices with optimal cut-offvalues in children with accuracy ≥90% were (in descending order): Matos & Carvalho index, MDHL(Telmissani) formula, England and Fraser formula, Pornprasert index, Sirachainan index, Telmissani (MCHD) formula, CRUISE index, Hameed index, Sargolzaie formula and Zaghloul II index. The CroThalDD-LM1 index has an accuracy of 93.36% (AUC 0.986, 95% CI 0.975-0.997), while the second CroThalDD-LM2 index utilizes absolute reticulocyte count alongside CBC variables, with an accuracy of 96.77% (AUC 0.985, 95% CI 0.988-0.999). Discussion and conclusion: We recommend using aforementioned formulas and indices with corrected cut-off values and accuracy >90% alongside two new proposed indices. A comparison of both native and these new indices is encouraged. These are the first discrimination indices generated and designed precisely for the pediatric population, which includes preschool children.

SUCCESSFUL RESOLUTION OF NUTCRACKER SYNDROME WITH 3D PRINTED PEEK EXTRAVASCULAR STENT IN AN ADOLESCENT BOY.

Three-dimensional printed polyetheretherketone (PEEK) extravascular stent was applied to treat a 14-year-old boy with nutcracker syndrome. Digital subtraction angiography revealed a segment of the left renal vein (LRV) with reduced contrast filling immediately before its inflow into the inferior vena cava, and high-pressure gradient. The three-dimensional reconstruction model demonstrated that the LRV and the duodenum were contracted at the aortomesenteric angle, resulting in LRV compression from the abnormal high-level duodenal compartment. When duodenum courses between the abdominal aorta and superior mesenteric artery (duodenal interposition), the LRV entrapment occurs even at <90 aortomesenteric degrees. Three-dimensional printed PEEK extravascular stent was chosen to elevate the superior mesenteric artery and lower the duodenum position, thus relieving LRV compression. This extravascular application has significant advantages over open surgery, endovascular stenting and artificial vessel procedures with expanded polytetrafluoroethylene. It provides better cellular vitality by ensuring soft tissue proliferation. By reducing external acceleration and centrifugal force, a three-dimensional printed PEEK extravascular stent reduces adverse side effects. Such a stent has a distinctive personalized design, good stiffness, and durability that allows blood vessel growth, preventing stent migration and thrombosis. Therefore, it is suitable for both adult and pediatric patients. According to the abdominal ultrasound and multi-slice computed tomography scan, the postoperative follow-up results were satisfactory one year after surgery. The patient felt well, the blood flow in the LRV was not obstructed, and the blood flow velocity was average. The external stent was in place.

Cystatin C, renal resistance index, and kidney injury molecule-1 are potential early predictors of diabetic kidney disease in children with type 1 diabetes.

Background: Diabetic kidney disease (DKD) is the main cause of end-stage renal disease in patients with diabetes mellitus type I (DM-T1). Microalbuminuria and estimated glomerular filtration rate (eGFR) are standard predictors of DKD. However, these predictors have serious weaknesses. Our study aimed to analyze cystatin C, renal resistance index, and urinary kidney injury molecule-1 (KIM-1) as predictors of DKD. Methods: We conducted a cross-sectional study in 2019 on a consecutive sample of children and adolescents (10-18 years) diagnosed with DM-T1. The outcome was a risk for DKD estimated using standard predictors: age, urinary albumin, eGFR, serum creatinine, DM-T1 duration, HbA1c, blood pressure, and body mass index (BMI). We conducted the analysis using structural equation modeling. Results: We enrolled 75 children, 36 girls and 39 boys with the median interquartile range (IQR) age of 14 (11-16) years and a median (IQR) duration of DM-T1 of 6 (4-9) years. The three focal predictors (cystatin C, resistance index, and urinary KIM-1) were significantly associated with the estimated risk for DKD. Raw path coefficients for cystatin C were 3.16 [95% CI 0.78; 5.53; p = 0.009, false discovery rate (FDR) < 5%], for renal resistance index were -8.14 (95% CI -15.36; -0.92; p = 0.027; FDR < 5%), and for urinary KIM-1 were 0.47 (95% CI 0.02; 0.93; p = 0.040; FDR < 5%). Conclusion: Cystatin C, renal resistance index, and KIM-1 may be associated with the risk for DKD in children and adolescents diagnosed with DM-T1. We encourage further prospective cohort studies to test our results.

A Limited Course of Eculizumab in a Child with the Atypical Hemolytic Uremic Syndrome and Pre-B Acute Lymphoblastic Leukemia on Maintenance Therapy: Case Report and Literature Review.

Acute lymphoblastic leukemia (ALL) is considered a possible risk for the occurrence of thrombotic microangiopathies. We present a girl with pre-B ALL successfully treated according to the BFM ALL IC-2009 protocol on maintenance therapy followed by aHUS occurrence. This is the seventh case of HUS/aHUS on ALL maintenance therapy and the first with clearly documented eculizumab use in the early stage of aHUS/secondary TMA. Standard and additional parameters were used in aHUS monitoring alongside the reticulocyte production index adjusted for age (RPI/A) and the aspartate aminotransferase-to-platelet ratio index (APRI) as markers of hemolysis and rapid response following treatment. RPI/A and APRI are markers of bone marrow response to anemia serving as red blood cell vs. platelet recovery markers. Together they mark the exact recovery point of thrombotic microangiopathy and serve as a prognostic marker of eculizumab treatment success. During the 8-month treatment and 6-month follow-up, no recurrence of hemolysis, ALL relapse, or renal damage were observed. A systematic review of the literature revealed 14/312 articles; five children had aHUS before the onset of ALL, and two children had both diseases concurrently. At least 3/7 patients are attributed to aHUS, of whom 2/7 have renal damage. Potential undiagnosed/unpublished cases may be assumed.

ESTIMATION OF THE GLOMERULAR FILTRATION RATE IN CHILDREN WITH HEMOPHILIA.

Estimated glomerular filtration rate (eGFR) is one of the best-performing methods in evaluating kidney function. There are limited data regarding the estimated glomerular filtration rate in children and young adults with hemophilia. The aim of this study was to determine the difference between three commonly used estimated glomerular filtration rate equations in the pediatric population in a cohort of patients with hemophilia. Our prospective study included 36 pediatric patients with moderate or severe hemophilia. eGFR was calculated for each patient using the original creatinine-based "bedside Schwartz" equation, the cystatin C-based equation and the creatinine-cystatin C-based equation. The difference between the equations, calculated using the one-way repeated ANOVA test, was statistically significant (p <0.001), and post hoc analysis found differences between each method. Correlation analysis showed the strongest positive correlation between the bedside Schwartz equation and creatinine-cystatin C-based equation (r=0.866) among the three methods examined. A correlation between the three eGFR methods was present, but with significant differences between them. Due to the observed differences between eGFR in pediatric patients with hemophilia, further research is needed to find the optimal measurement method for eGFR. Nevertheless, we recommend implementing eGFR equations in routine clinical monitoring of pediatric patients with hemophilia.

Early biochemical markers in the assessment of acute kidney injury in children after cardiac surgery.

Our aim was to evaluate biochemical markers in plasma (NGAL, CysC) and urine (NGAL, KIM-1) in children's early onset of acute kidney injury after congenital heart defect surgery using cardiopulmonary bypass. This study prospectively included 100 children with congenital heart defects who developed AKI. Patients with acute kidney injury had significantly higher CysC levels 6 and 12 h after cardiac surgery and plasma NGAL levels 2 and 6 h after cardiac surgery. The best predictive properties for the development of acute kidney injury are the combination (+CysCpl or +NGALu) after 12 h and a combination (+CysCpl and +NGALu) 6 and 24 h after cardiac surgery. We showed that plasma CysC and urinary NGAL could reliably predict the development of acute kidney injury. Measurement of early biochemical markers in plasma and urine, individually and combination, may predict the development of cardiac surgery-associated acute kidney injury in children.

Genotype-phenotype Correlation of ß-Thalassemia in Croatian Patients: A Specific HBB Gene Mutations.

An analysis of genotype-phenotype correlation was performed for 14 patients with beta-thalassemia who had been registered in Referral Centre for hematology and oncology of the University Hospital Centre, Zagreb, Croatia. HBB gene mutations were determined using a gene-specific Q5 High-Fidelity PCR analysis with direct DNA sequencing of amplified transcripts. Mahidol score index used for classification of thalassemia severity was found to be low for all the patients enrolled in the study, indicating a mild ß-thalassemia phenotype with no signs of disease progression. Most of the patients have already described gene mutations: IVS-II-666 C>T (HBB:c.316-185C>T) and IVS-II-16 G>C (HBB:c.315+16G>C). Each of the aforementioned mutations was found in (11/14; 78,57%) and (10/14; 71,43%) of our patients, respectively. Recently published HBB:c.9T>C mutation was found in 8 of 14 (57,14%) in our study group. IVSII-74 T>G (HBB:c.315+74T>G) is a worldwide mutation found in 6 of 14 (42.86%) of our patients. All these mutations occur among Croatian children with no obvious Indian/Near Eastern/Iranian ancestry. We also identified 7 de novo mutations (c.316-135het_dupT, c.316-133A>G, c.93-54G>A, c.316-68_316-67het_insCGG, c.316-342delA, c.316-312delT, c.316-209delT) of mild severity phenotype according to Mahidol classification score index. We did not find children or adults with thalassemia major severity phenotype.

Association of Generalized Psoriasis and Mixed Glomerulonephritis in a 10-year-old Girl.

Generalized psoriasis and renal function disorder were previously described in sporadic adult cases, revealing a new entity - psoriatic nephropathy. So far there have been only two cases describing this association in children. We present and discuss a case of 10-year-old girl with the unique biopsy findings of double glomerulonephritis associated with the simultaneous onset of generalized psoriasis.

[C1Q NEPHROPATHY: CASE REPORTS AND LITERATURE REVIEW]. / C1Q-NEFROPATIJA: PRIKAZI BOLESNIKA I PREGLED LITERATURE.

C1q nephropathy is considered a form of glomerulonephritis, defined by histological findings of dominant Clq immune deposits in renal biopsy. It is a rare disease, most often manifested in children and young adults. The most common clinical manifestation of the disease is nephrotic syndrome, but other renal syndromes could also be found. The cause of the disease is not known, but the immune pathogenesis could be assumed. Often, resistance to glucocorticoid or other immunosuppressive therapy is present, potentially leading to chronic renal insufficiency. We present ten patients with renal biopsy and clinical findings of Clq nephropathy. None of the patients had clinical or serological manifestations of systemic lupus. All patients had normal findings of C3 and C4 components of complement, as well as normal ANF, anti-dsD-NA and ANCA antibodies.

Ultrasound distinction between simple recurrent urinary tract infections and a specific bladder wall inflammatory entity called cystitis cystica.

A specific representative of recurrent urinary tract infections (UTI) called cystitis cystica (CC) was assessed by ultrasound. The aim of the study was to delineate, by means of ultrasound measurement (US) of bladder wall thickness (BWT), the children with mere repeated UTI from those prone to frequent UTI due to CC. Two groups were compared, the control group of 30 with recurrent UTI without US CC BWT changes, and the group of 30 children with characteristic CC bladder wall thickening in whom cystoscopy was performed for verification the diagnosis of CC. BWT of > 3 mm (> 2.8 mm and > 3.3 mm) was found as cut-of value for distinction of CC versus simple recurrent UTI. US BWT measurement is useful in diagnosing CC and therefore valuable in decision about need of UTI prophylaxis.

Childhood-onset systemic lupus erythematosus in Croatia: demographic, clinical and laboratory features, and factors influencing time to diagnosis.

OBJECTIVES: Childhood-onset systemic lupus erythematosus (cSLE) presents with diverse clinical features and often with non-classical symptoms that may delay diagnosis and increase risk of morbidity and mortality. This paper aims to analyse incidence, and clinical and laboratory features of cSLE in Croatia between 1991 and 2010, and to identify factors influencing time to diagnosis. RESULTS: Medical records at three university-based tertiary care centres were analysed retrospectively for 81 children with cSLE (68 girls). Mean age at onset was 13.4±2.8 yr (interquartile range 3), and annual incidence varied from 1-15 per million at risk. The most frequent clinical and laboratory features were musculoskeletal symptoms (80%) and increased erythrocyte sedimentation rate (96%). The most frequent immunological laboratory findings were the presence of antibodies against histones (86%), double-stranded DNA (73%), and Sm protein (64%), as well as low levels of C3 complement (69%). Haematuria was present in 58% of children, proteinuria in 56%, and biopsy-confirmed lupus nephritis in 43%. Median time from symptom onset to diagnosis was 2 months (range 0-96). Time to diagnosis was inversely associated with ECLAM score (p<0.001), but it showed no association with age, gender, clinical features or distance from the nearest paediatric centre. CONCLUSIONS: This is the first large-scale, in-depth study of clinical and laboratory features of cSLE in Croatia. Among all demographic, laboratory and clinical features examined, ECLAM score alone was inversely associated with time to diagnosis. This highlights the need to improve detection of children with fewer symptoms early in the course of the disease, therefore serious consequences for prognosis could be avoided.

Ultrasound bladder wall thickness measurement in diagnosis of recurrent urinary tract infections and cystitis cystica in prepubertal girls.

OBJECTIVE: To evaluate urinary bladder wall thickness (BWT) assessed by ultrasound as a diagnostic tool for cystitis cystica. PATIENTS AND METHODS: This was a 9-year prospective study comprising 120 prepubertal girls. Sixty subjects of whom half underwent cystoscopy represented cases while the other 60 (those with a single urinary tract infection and healthy subjects) represented controls. RESULTS: Based on receiver operating characteristics (ROC) analysis, BWT discriminated very well between cases and controls with area under the ROC curve close to 1.0. At the optimum cut-off defined at 3.9 mm, negative predictive value (NPV) was 100% leaving no probability of cystic cystitis with BWT <3.9 mm. Positive predictive value (PPV) was also very high (95.2%), indicating only around 4.82% probability of no cystic cystitis in patients with BWT values ≥3.9 mm. BWT could also distinguish between healthy subjects and those with a cured single urinary tract infection, although discriminatory properties were moderate (area under ROC 86.7%, PPV 78.8%, NPV 85.2%). CONCLUSION: Ultrasound mucosal bladder wall measurement is a non-invasive, simple and quite reliable method in diagnosis of cystitis cystica in prepubertal girls with recurrent urinary tract infections.

Polyarteritis nodosa in Croatian children: a retrospective study over the last 20 years.

To analyze the disease characteristics, treatment modalities and outcome of polyarteritis nodosa (PAN) in Croatian children. Cross-sectional study included all children with PAN diagnosed according to EULAR/PRES/PRINTO criteria during the last two decades. PAN was diagnosed in 12 patients (6 girls and 6 boys) mean age (±SD) 11.33 ± 3.08 years. The share of PAN among all vasculitides was 3.8 %. Systemic PAN was diagnosed in 7 children (58 %), microscopic polyangiitis in 3 (25 %), cutaneous PAN in 2 (17 %). The most consistent symptoms were skin involvement (90 %) and arthritis/arthralgia (60 %). The CNS was affected in 33 % of patients. Inflammatory markers (C-reactive protein and erythrocyte sedimentation rate [ESR]) were elevated in all patients, and anti-neutrophil cytoplasmatic antibodies were positive in all patients with microscopic polyangiitis. Therapy mode for all patients was corticosteroids. Immunosuppressive drugs were used as additional therapy for patients with severe symptoms. Two patients (17 %), both suffering from microscopic polyangiitis, died due to renal failure during the follow-up. In comparison with available studies, we found a difference in distribution of childhood polyarteritis nodosa as well as some clinical characteristics (e.g., higher prevalence of neurological and pulmonary symptoms), while other researched features, laboratory and treatment were similar.

Positive feedback loop for cystitis cystica: the effect of recurrent urinary tract infection on the number of bladder wall mucosa nodules.

The main purpose of this study was to demonstrate positive feedback loop between bladder wall nodules (nodules being one of the key diagnostic factors), bladder wall thickness, and recurrent urinary tract infections. Cystitis cystica was diagnosed in 115 prepubertal girls (mean age 7.79 +/- 3.05 years) by optic examination of bladder mucosal nodules and by ultrasonographic measurement of bladder wall thickness. Bladder wall thickness increased with the frequency of recurrent urinary tract infections as well as with the number of nodules on bladder wall mucosa (3.52 +/- 0.522 mm < or = 5 nodules vs. 4.42 +/- 0.429 mm 6-10 nodules vs. 5.20 +/- 0.610 mm > 10 nodules, respectively). Study results suggested that early control of urinary tract infections by chemoprophylaxis could prevent higher grades of bladder wall mucosal changes and consequently shorten the length of chemoprophylaxis.

Idiopathic nephrotic syndrome in children: review of 282 Croatian cases.

Recent data suggests increased incidence of focal segmental glomerulosclerosis (FSGS) among children with idiopathic nephrotic syndrome (INS). To determine the causes and possible longitudinal changes in the etiology of INS, 282 Croatian children diagnosed with INS between 1990 and 2009 were evaluated. In total, 122 children were assessed as having minimal change nephrotic syndrome (MCNS) based on their initial presentation, laboratory findings and clinical course. Kidney biopsy was performed in the remaining 160 children. MCNS was present in 18.1% of all biopsies performed. Total incidence of MCNS (assessed + biopsy proven) was only 53.5%. In contrast, FSGS was found in 40.6% of all biopsies and accounted for 23.1% of all cases. Mesangial proliferative glomerulonephritis (MesPGN) was the third most common diagnosis, present in 26.9% of the biopsies, and accounted for 15.2% of all cases. There were no significant longitudinal differences in the incidence of different causes of INS. The overall response to steroids at presentation was 71.6%. A higher proportion of initial steroid responders among children with FSGS (43.1%) and MesPGN (67.4%) than previously reported was noted. A longitudinal tendency of increasing steroid resistance in FSGS and MesPGN groups was observed.

Cystitis cystica and recurrent urinary tract infections in children.

The pathogenesis of recurrent urinary tract infections (UTIs) in preschool children with anatomically correct urinary tract (UT) is rather obscure. In girls, the bladder wall changes of cystitis cystica (CC) may be per se responsible for UTIs recurrence. During the 20-year period, 127 preschool children (125 girls; median age: 6.1 years) with CC, in whom UT anomalies were excluded, were diagnosed. The mean duration of UTIs symptoms prior to diagnosis was 3.31 +/- 2.51 years. Cystoscopical findings were labelled as mild, moderate and severe in 22.8%, 39.4% and 37.8% of patients, respectively. Following the confirmation of CC, long-term chemoprophylaxis with sulfamethoxazole-trimethoprim/nitrofurantoin was administered. A one year UTI-free period after chemoprophylaxis discontinuation was defined as therapeutic success. With 2.5 years median duration of regular chemoprophylaxis this goal was achieved in 58 children mainly with mild/ moderate CC. Thirty children from "improved/unchanged" group taking regular prophylaxis had significant reduction of UTIs ("improved"). Only 12 children belonging to the same group taking regular prophylaxis and all children with irregular prophylaxis had approximately the same number of UTIs as before treatment ("unchanged"). The "improved/unchanged" outcomes were predominantly found in children with severe form of CC. Although urodynamic disturbances detected in more than 50% of patients in whom urodynamics was performed were not found influential on the disease outcome, they could be responsible for its development. The results of our study suggest that regular and long-lasting chemoprophylaxis remains a basis for successful treatment for majority of patients with CC, even those with severe forms. If not treated properly with chemoprophylactic agents and without fair compliance in taking drugs, the disease is prone to recurrent UTIs.

[Clinical and histopathological characteristics of biopsy-proven renal diseases in Croatia]. / Klinicke i patohistoloske karakteristike biopsijom dokazanih bubreznih bolesti djece u Hrvatskoj.

There is little data on the spectrum of renal diseases in children in Croatia. The Croatian Society for Pediatric Nephrology has established the Registry of Biopsy-Proven Renal Diseases in an attempt to address this issue nationwide. Here we report preliminary results of a retrospective analysis of clinical and histopathological data of 565 children aged < or =17 years presenting to 9 hospitals in Croatia from 1991 to 2004, in whom kidney biopsy was performed. The most common indication for renal biopsy was nephrotic syndrome (39.1%), followed by asymptomatic proteinuria/hematuria (22.0%) and acute nephritic syndrome (17.0%). All biopsies were analysed by light-, immunofluorescent and electron microscopy. The majority of children, 552 out of 565 (92.4%), had glomerulonephritis (GN). Tubulointerstitial nephritis was found in 16 (2.8%), congenital renal parenchyma anomalies in 14 (2.5%) and vascular disease in 11 (1.9%) cases. One (0.2%) child had sarcoidosis with nephrocalcinosis. The sample was non-diagnostic in 1 (0.2%) case. Among children with GN, primary GN accounted for 70.9%, secondary GN for 16.1% and hereditary GN for 13.0% cases. The most frequent primary GN forms were focal segmental glomerulosclerosis (FSGS) (24.6%), mesangial proliferative glomerulonephritis (MEPGN) (19.2%) and IgA nephropathy (18.1%). Acute GN in resolution was found in 11.1% and minimal changes GN in 6.8% of cases. Most children with secondary GN had nephritis of Henoch-Schönlein purpura (HSP) (54.7%) and nephritis of systemic lupus erythematosus (SLE) (40.5%), while among hereditary GN Alport syndrome was most common (80.9%). In the group of children with primary GN who presented with nephrotic syndrome, most common forms were FSGS (38.5%) and MEPGN (24.0%). Minimal changes GN accounted for only 10.9% of cases. IgA nephropathy, primary or related to HSP (20.0%), FSGS (16.1%), MEPGN (12.6%) and Alport syndrome (9.7%) were the most common biopsy-proven renal diseases in Croatian children. The analysis provided data on the frequency of histological renal lesions in children in Croatia. The higher frequency of FSGS and MEPGN among Croatian children in comparison with other countries deserves further evaluation.