Chronic kidney disease (CKD) in children is a global problem worldwide. The article discusses the problem of stratification of CKD severity according to the classifications of the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (NKF-K / DOQI) (2002) and Kidney Disease Improving Global Outcomes (KDIGO) (2012) in pediatric patients. There are limitations in assessing severity of CKD stages C1-5 according to NKF-K / DOQI (2002) and KDIGO (2012) in children under 2 years of age who have a low glomerular filtration rate in contrast to adults. The stratification of the severity of stages 1-5 of CKD, cardiovascular complications and renal prognosis in children and adolescents according to the classifications NKF-K / DOQI (2002) [3] and KDIGO (2012) [14] are discussed. In adult patients with CKD, there is a compelling case for identifying of C3a and C3b sub stages in 3 stages of CKD according to KDIGO (2012) was that renal and cardiovascular prognosis are different with GFR 45-59 ml/min/1.73 m 2and GFR 30-44 ml/min/1.73 m 2 . The prognosis of the risk of developing cardiovascular diseases and complications for stages C2-5 in accordance with the KDIGO classification (2012) in children and adults differ. As follows from the publications, children with CKD in the pre-dialysis stages C2-4 form a high-risk group, with C4-5 on dialysis a group of very high risk of complications associated with cardiovascular pathology. Cardiovascular complications account for more than 30 % of all deaths of pediatric patients with CKD C4-5 on dialysis. The arguments justifying the allocation of CKD stages C1-5 in children under 2 years of age in accordance with the classification of NKF-K/DOQI (2002) are presented.

The review presents materials on the prevalence of NS in children, variants of its course: steroid-sensitive (SSNS) and steroidresistant (SRNS) steroid-dependent (SSNS). Minimal change nephrotic syndrome minimal changes (NSMC) is the most common glomerular disorder. Although NSMC has an excellent prognosis with a low risk of progression to t-CRF, its recurrent nature requires children to receive frequent courses of steroid therapy and other medications, many of which are known to affect blood pressure (BP). The interrelation of NS in children with arterial hypertension (AH) is shown. Prevalence of hypertension in children with SCNS, SRNS, SZNS is given. The regulation of hypertension in children is mandatory in the treatment of NS, due to the fact that hypertension is not established in a timely manner, is insufficiently controlled and is often masked. Vascular dysregulation, fluid overload, increased cardiac output and peripheral vascular resistance, alone or in combination, can lead to hypertension in CKD. The use of modern methods to monitor and control blood pressure is critical for improving hypertension management and preventing target organ damage in children. 24-hour blood pressure measurements are an important tool in determining the prognosis and treatment of children with HC. Many comorbidities increase the risk of cardiovascular disease, including obesity, left ventricular hypertrophy (LVH), increased arterial stiffness (increased BMI, endothelial dysfunction), impaired glucose metabolism, and hyperlipidemia. The pathophysiological aspects of hypertension in children with NS are considered. The pathophysiology of hypertension in NS is complex, with many renal and extrarenal factors. Renal factors include sodium retention, fibrosis / decreased GFR, and progression of kidney disease, and a direct link between albuminuria and blood pressure has recently been described. Other factors include drug side effects, comorbidities and genetic predisposition. Sodium metabolism plays an important role in the development of edema and blood pressure regulation in NS. There are two main hypotheses for sodium retention in NS, the hypothesis of underfilling and overfilling. The role of the epithelial sodium channel (ENC), atrial natriuretic peptide (ANP), nitric oxide (NO), steroid hormones and other drugs in sodium retention and the pathogenesis of hypertension is also considered. In children with NS, hypertension leads to target organs damage (TOD): left ventricular hypertrophy (LVH), damage to the organ of vision, cognitive impairment and more rapid progression of chronic kidney disease. Salt restriction and RAAS inhibition are considered integral parts of the treatment of children with proteinuria, and both are known to have blood pressure lowering effects. The RAAS blockade has a renoprotective effect in patients with glomerular damage. Studies have found greater reductions in proteinuria with ACE / ARB combination therapy. This renoprotective effect is explained by both a decrease in blood pressure and mechanisms independent of blood pressure. Lifestyle modifications, weight control, healthy eating, reduced sodium intake, supportive exercise, and basic drug therapy using angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), diuretics can slow the progression of NS in children.

Fraser syndrome (OMIM # 219000; ORPHA: 2052; ICD-10: Q87.0) is a rare, disease with an autosomal recessive type of inheritance is characterized by abnormalities in the development of the eyes, kidneys, larynx, ears, and bone systems (cryptophthalmos, syndactyly, abnormalities of the kidneys, urogenital tract, and respiratory system). The article presents current literature data on the phenotypic and genotypic features of Fraser syndrome, the management of patients with new opportunities for genetic diagnosis and treatment. The syndrome, described by D. Fraser in 1962, is caused by mutations in the FRAS1, FREM2, GRIP genes. The diagnosis of the Fraser syndrome phenotype is established in the presence of the main criteria (cryptophthalmos, syndactyly, abnormalities of the urinary and respiratory system, genitals, family history indicating a closely related marriage) and secondary (congenital malformations of the nose and ears, skull ossification defects, anorectal abnormalities, umbilical hernia, etc.). Molecular genetic testing proves a rare disease, requires genetic counseling. The management of patients is carried out jointly by an ophthalmologist, an otolaryngologist, an audiologist, a nephrologist, a urologist, a maxillofacial surgeon and other specialists.

Hemolytic uremic syndrome (HUS) associated with shiga toxin E. coli(STEC) is one of the most common causes of acute kidney injury in young children. The share of STEC-HUS among all HUS variants is up to 90%. Not all STECs are pathogenic to humans, and those that cause disease (hemorrhagic colitis, HUS) are referred to as enterohemorrhagic E. coli(EHEC). The main pathogens causing STEC-HUS include the serotype E. coliO157: H7, less often serotypes O26, O80, O103, O121, O145. EHEC exist as normal microbiota in cattle, but can also be found in goats, sheep, pigs, chickens, dogs, and rats. Infection can occur when using undercooked ground beef, unpasteurized milk, water, including tap water and from open ponds and pools, from an infected person and when visiting farms and zoos. The epidemiological history should be carefully assessed in each patient with HUS, taking into account the annual outbreaks of this disease in different regions of the world. In recent years actively discussed the issue of the transfer of shiga toxin (Stx) from the intestine to the blood and from the blood to target organs in the form of microvesicles, the wall of which is the outer shell of E.coliand blood cells. This allows Stx to escape the response of the human immune system. The article describes in detail the mechanisms of infection and expression of pathogenic genes of EHEC, the effect of Stx on endothelial cells, on expression of adhesion molecules and inflammatory chemokines, activation of the alternative complement pathway, which determine the development of HUS.

Typical hemolytic-uremic syndrome (tGUS) is an acute disease in which non-immune microangiopathic hemolytic anemia, thrombocytopenia and acute renal damage develop against the background of infection-related diarrhea in the prodromal period. Hemolytic-uremic syndrome is the main cause of acute kidney injury in children under 5 years of age. Hemolytic-uremic syndrome is one of the causes of the progression of renal dysfunction in children with the formation of chronic kidney disease. The clinical picture of hemolytic-uremic syndrome is characterized by multi-organ manifestations with symptoms of acute renal damage, damage to the gastrointestinal tract, nervous, cardiovascular, respiratory systems and hemostasis. The article presents the data of modern literature on the epidemiology, etiology, pathogenesis and clinical picture of HUS in children, own scientific results on the clinical and paraclinical characteristics of a typical hemolytic-uremic syndrome in children of the Orenburg region.

Orphan Hereditary Hypophosphatemic Rickets with Hypercalciuria (HHRH) (OMIM: 241530; ORPHA: 157215) with an autosomal recessive mode of inheritance occurs with an estimated prevalence of 1: 250,000 in the child population. HHRH was first described by M. Tieder, et al. (1985). The syndrome is caused by heterozygous or homozygous mutations in the SLC34A3 gene mapped to chromosome 9q34.3, which encodes a type II sodium phosphate cotransporter (NaPiIIc). Mutations result in loss of NaPi-IIc function and impairment of phosphate reabsorption in the proximal renal nephron. HHRH is characterized by a decrease in phosphate reabsorption in the proximal nephron tubules, manifested by hyperphosphaturia, hypercalciuria, hypophosphatemia, an increase in the concentration of 1,25(OH) 2D3, a decrease in parathyroid hormone (PTH) circulating in the blood, osteomalacia, inhibition of growth, low corrosiveness, low corrosiveness. The article presents the characteristics of the phenotype and genotype of HHRH, diagnostic criteria and treatment strategy. A description of a clinical case of HHRH with hypercalciuria, nephrocalcinosis and urolithiasis due to mutation of the SLC34A3gene is presented.

The aim of the study was to analyze the rate of progression of IgA nephropathy (IgAN) in childhood and factors affecting prognosis. The study included 54 children with a morphologically verified diagnosis of IgAN (36 boys, 18 girls) aged 2 to 17 years, who were under observation in the nephrology department of the "2nd Children's City Clinical Hospital" of the National Center for Pediatric Nephrology and Renal Replacement therapy in Minsk in the period from 2013 to 2020. The participation of deGal-IgA1, markers of T- and B-lymphocyte activation, pro-inflammatory and pro-fibrotic molecules in the development of the disease has been shown. AG was registered in 18 of 54 (33,3 %) children, nocturnal AG in 11/43 (23,4 %), signs of cardiac remodeling in 10/49 (20,4 %). A decrease in the level of adiponectin, vitamin D, an increase in obestatin in comparison with healthy children makes it possible to attribute patients with IgAN to the risk group for the development of cardiovascular disorders, which implies the need for timely monitoring and correction. In most cases in childhood IgAN is characterized by a benign course without signs of progression. The prognostic significance of highly active nephritis, impaired renal function at the onset of the disease, T1 (tubular atrophy / interstitial fibrosis in 25–50 %) by MEST, proteinuria over 0,8 g/24 hours as risk factors for progression was shown.

THE AIM:to describe the causes, pathogenesis, clinical course and outcome of Potter sequence in children with cystic kidney disease. PATIENTS AND METHODS:the follow-up study of 23 newborns with cystic kidney disease was studied, in which renal oligohydramnios (ROH) was confirmed prenatally by ultrasound (US). RESULTS:Of the 155 children with autosomal dominant polycystic kidney disease (ADPKD), 8 (5,2 %) prenatal after 30 weeks of gestation established ROH, at 26-32 weeks of gestation – cyst in the kidney by US, in 2 of them ROH confirmed simultaneously with the detection of cysts in kidneys of a fetus, 6 – late detection of kidney cysts. Of the 8 newborns with a very early onset ADPKD, prenatal developed in ROH conditions, in 2 (25 %) in the neonatal period diagnosed the Potter phenotype. Of the 20 children with autosomal recessive polycystic kidney disease (ARPKD), 12 (60 %) prenatally revealed ROH after 18 weeks of gestation prenatally, of these, 8 (67 %) in the neonatal period diagnosed the Potter phenotype. Of the 12 newborns with ARPKD, that developed in ROH conditions, in 5 (42 %) kidney cysts were detected prenatally by US at 32-37 weeks of gestation, in 7 (58 %) in the neonatal period. ROH and the Potter phenotype are more common with ARPKD in the fetus than with ADPKD. Among children with ARPKD and ADPKD undergoing ROH, no statistically significant differences in the frequency of deaths in the neonatal and infancy. The characteristics of course and outcome of the Potter sequence in the neonatal and infant periods in a boy with deletion of 12p and cystic kidney disease are described. ROH in 2 children with cystic kidneys and coloboma of the optic nerve disc did not lead to the formation of the Potter phenotype. In 15 children with multicystic kidney prenatal US showed no ROH. CONCLUSION: the results of a follow-up study of children after ROH and the course of the Potter sequence for different cystic kidney disease in children are presented.

Alport syndrome is a progressive multisystem disease associated with variants in genes COL4A3, COL4A4, COL4A5.The syndrome is an important genetic cause of kidney failure, including women with X-linked disease. Given the unfavorable natural history of Alport nephropathy and benefit from early treatment with angiotensin-converting enzyme inhibition, it is necessary to change our diagnostic approach in patients with persistent glomerular hematuria and management of patients with Alport syndrome. This review presents the ethiology, pathogenesis, genotype and phenotype heterogeneity of the syndrome and expert clinical practice recommendations to enhancing early diagnosis and achieving optimal outcomes in Alport syndrome.

CAKUT-syndrome includes combined congenital abnormalities of the kidneys and urinary tract and is a complex problem in pediatrics, requiring an interdisciplinary approach of doctors of various specialties. One of the most severe manifestations of CAKUT-syndrome is vesicoureteral reflux, which is often the main manifestation of a congenital abnormality of the kidneys and urinary tract. Structural and urodynamic disorders in the organs of the urinary system in vesicoureteral reflux can lead to the formation of reflux nephropathy and chronic kidney disease. Low-symptom clinical manifestations of reflux nephropathy make it difficult to diagnose it early. Vesicoureteral reflux leads to intrarenal reflux, repeated attacks of pyelonephritis and sclerosis of the renal tissue, which in 25-60 % of cases causes end-stage chronic renal failure due to vesicoureteral reflux. Given the absence of specific pathognomonic clinical manifestations of reflux nephropathy, laboratory indicators are of fundamental importance in the diagnosis-levels of albuminuria, leukocyturia, urinary sediment fermenturia, urine osmolarity, daily urinary excretion of β2 – microglobulin and a wide arsenal of methods for diagnosing reflux nephropathy and scarring of the renal parenchyma: ultrasound with dopplerography of the renal blood flow, magnetic resonance imaging and computed tomography, radioisotope scanning. The imperfection of instrumental methods for visualizing the initial stages of kidney fibrosis dictates the need to develop alternative, more sensitive methods for early diagnosis of reflux nephropathy. One of the directions of this search is molecular diagnostics, which allows you to detect possible damage to the renal tissue at the subcellular level long before the clinical manifestations of pathology, personify nephroprotective therapy and prevention of reflux nephropathy. The article presents clinical observations from our own practice of late diagnosis of reflux nephropathy, in which renal pathology was first detected at stages 5 and 3 of chronic kidney disease in two boys aged 10 and 16 years, respectively, who were on inpatient treatment in the Nephrology Department of the Children's Republican clinical hospital.

BACKGROUND.  The article presents the case of a clinical and laboratory complex of a recurrent hormone-sensitive variant of nephrotic syndrome in a patient with leucinosis (maple syrup disease). THE AIM: to study the clinical laboratory features of nephrotic syndrome in a child with orphan disease – leucinosis. A PATIENT. A 4-year-old child born in a consanguineous marriage, who had previously been diagnosed with a rare genetic disease leucinosis, was examined. The manifestation of leucinosis began from the 8th day of birth. Based on the results of a molecular genetic study the diagnosis was pinpointed as leucinosis with an autosomal recessive mode of inheritance, classic neonatal (maple syrup disease). At the age of 4 the child developed a clinical and laboratory complex of nephrotic syndrome. RESULTS.  The onset of nephrotic syndrome was characterized by a hormone-sensitive course. After completion of the course of glucocorticosteroid therapy, there was a relapse because of acute respiratory infection which also turned out to be hormone-sensitive. Kidney function was not impaired. There were no crises of leucinosis due to nephrotic syndrome. CONCLUSION. Taking into account the development of nephrotic syndrome in a child with a genetically determined disease, a molecular genetic examination should be done to exclude the hereditary nature of the developed nephrotic syndrome. The examination is of great clinical importance for determining treatment tactics, cytostatic therapy, doing a kidney biopsy in order to determine the morphological form of glomerulonephritis, prognosis of progression to the end-stage renal failure.