Sergey Bondarenko

Introduction. Obstruction of the pyeloureteral junction (PUJO) of the horseshoe kidney is a very rare disease both in adults and children. This is the reason for the small number of scientific works on the subject of pyeloplasty for this pathology in children. Isthmus crossing and nephropexy followed by dissecting pyeloplasty have been suggested as one of the surgical treatment options. There are no convincing data on the feasibility of this procedure in the literature. The aim of our work was to evaluate 25 years of experience in the treatment of PUJO of horseshoe kidney in children. Materials and Metods. A few small cohort studies have reported the efficacy of pyeloplasty for horseshoe kidney in children, and a limited number of studies have compared different operative treatments. It was these facts that prompted us to perform this work. We retrospectively evaluated the results of 112 pyeloplasties in 105 children from 1999 to 2024. Patients were divided into 3 groups according to the method of surgical intervention: open pyeloplasty with isthmotomy, open pyeloplasty without isthmotomy, laparoscopic pyeloplasty. We also divided the patients into 4 groups according to the method of urinary tract drainage. Resulrs. Clinical data and outcomes were further analyzed. We obtained positive results when performing pyeloplasty in 92.9% of patients. There was no significant difference in pyeloplasty results between the groups. We also found no statistically significant differences in the methods of urinary tract drainage. Conclusion. Today, preference should be given to minimally invasive method of treatment in children, even in such a complex malformation as hydronephrotic transformation of the horseshoe kidney, taking into account comparable results with the open method of treatment and the unconditional advantages of laparoscopic access in the form of early rehabilitation of the child, minimal pain syndrome and cosmeticity of this method.

In this paper we consider a high energy scattering of free scalar particles through a gravitational field. The one particle t-channel amplitude of the scattering in this limit is governed by reggeized graviton. Therefore, we discuss an appearance of the reggeized gravitons in the framework of Einstein–Hilbert gravity and consider Lipatov’s effective action for the reggeized gravitons. We calculate the trajectory of the corresponding t-channel amplitude in the framework and thereafter define the leading order amplitude of scattering of two massive scalar particles. An impact factor of the interaction of scalar particle with the reggeized gravitons is also calculated and possible applications of the approach are discussed as well.

A model of an extended manifold for the Dirac spinor field is considered. Two Lagrangians related by charge-parity-time-mass symmetry are constructed for a pair of the Dirac spinor fields with each spinor field defined in a separate manifold. An interaction between the matter fields in the manifolds is introduced through gravity. A fermionic effective action of the general system is constructed and a tadpole one-loop spinor diagram and part of the one-loop vacuum diagrams with two external gravitational off-shell fields which contribute to the effective action are calculated. It is demonstrated that among different versions of the second spinor Lagrangian there is a special one for which a cancellation of the mentioned diagrams in the total effective action takes place. As a result, the diagrams do not contribute to the cosmological constant, as well there is a zero contribution of the zero point energies of the spinor fields to the action. The non-zero leading order value of the cosmological constant for each manifold in the framework is proportional to the trace of an momentum–energy tensor of each separated manifold or difference of the tensors of the related manifolds. The result is depending on the chosen model of interaction of gravitational fields with fermions, the different possibilities are discussed. An appearance of the dark matter in the model is shortly discussed as well as further applications of the approach and it is interconnections with other cosmology models.

Theoretical possibilities of models of gravity with dynamical signature are discussed. The different scenarios of the signature change are proposed in the framework of Einstein-Cartan gravity. We consider, subsequently, the dynamical signature in the model of the complex manifold with complex coordinates and complex metrics are introduced, a complexification of the manifold and coordinates through new gauge fields, an additional gauge symmetry for the Einstein-Cartan vierbein fields, and non-flat tangent space for the metric in the Einstein-Cartan gravity. A new small parameter, which characterizes a degree of the deviation of the signature from the background one, is introduced in all models. The zero value of this parameter corresponds to the signature of an initial background metric. In turn, in the models with gauge fields present, this parameter represents a coupling constant of the gauge symmetry group. The mechanism of metric determination through induced gauge fields with defined signatures in the corresponding models is considered. The ways of the signature change through the gauge field dynamics are reviewed, and the consequences and applications of the proposed ideas are discussed as well.

Introduction. Urinary obstructions caused by foreign bodies (FB) represent quite a rare clinical case in practicе of pediatric urologists. However, some recent publications note a tendency towards higher occurrence of FB in urinary tracts in children. Most publications on FB urinary obstructions in children are devoted to the descriptions of individual medical cases. Considering the lack of multicenter research works on the problem, a study based on generalized clinical experience of several hospitals appears relevant. Materials and methods. The study is based on retrospective analysis of treatment results of 44 pediatric cases from 10 clinics of Russia and Belarus during the period from 2000 through 2020. The study population comprised 28 (63.3%) boys and 16 (36.4%) girls. Mean age of the patients was 10.9±3.7 years. The children were subdivided into two groups: group I included 28 (63.3%) cases where FB had been introduced in the urethra or bladder by the child; group II included 16 (36.4%) cases where foreign bodies ended up in urinary tracts as a result of instrumental or surgical procedures. Results. Clinical manifestation of FB was typical among the patients in the group I while in group II the condition more often occurred inapparently. Children often concealed FB introduction in the urinary tracts, and so contacts with a healthcare institution were ordinarily triggered by changes in urine analysis findings. Concealment of FB introduction in the urinary tracts determined help seeking start later than 7 days following the incident in 64.2% cases of group I. More than a half of the FB in children of group I were revealed within the first month after the incident. In group II, FB were revealed accidentally during follow-up examinations in 75% of the children. Transurethral FB extraction succeeded in 50% of the patients in group I. In group II, transurethral FB extraction was performed in 5 (31.3%) children. In 2 cases (12.5%), FB were extracted using flexible ureteroscopy. Percutaneous nephroscopy was used in 2 (12.5%) patients. 5 (31.3%) cases required pyelotomy with laparoscopic access, and in 2 (12.5%) patients a lumbotomy had to be carried out. Discussion. The rarity of FB of the urinary tract in the practice of a pediatric urologist is the reason for the combination ofthe existing experience in providing medical care to children from 11 centers. Delayed demand for medical care was noted if FB were introduced by the child independently. The generalized material shows that in childhood, the same approaches to FB extraction are applicable as in adult patients; endoscopic FB removal is optimal. Conclusions. In most cases of children suffering from foreign bodies in urinary tracts, the FB can be extracted using endoscopy without complications and with favourable outcome.

Introduction. Endoscopic dextranomer/hyaluronic acid copolymer (DxHA) injection is the most commonly used minimally invasive method of surgical treatment of vesicoureteral reflux (VUR) in children.Purpose of the study. To estimate the accuracy of logistic prognostic models and artificial neural network for prediction a single endoscopic injection DxHA in VUR.Materials and methods. We used endoscopic DxHA in 582 patients (783 ureteric units) of all grades reflux (I - 20, II - 133, III - 443, IV - 187), 53 ureters had complete duplication. A total effectiveness of surgery was 53.2%. A binary logistic regression model and an artificial neural network (multilayer perceptron) were created, taking the following as independent variables: grade of reflux, the patient's age and sex, the ureteral duplication and ureteral dilatation index.Results. The univariate logistic regression showed that the selected predictors were strongly related to the outcome of the treatment. Binary logistic regression and neural network developed high accuracy of the predictions, area under ROC-curve was 0,7 for logistic regression model (a sensitivity of 70.7%, and a specificity of 66.3%) and 0.74 for artificial neural network (a sensitivity of 85.5%, a specificity of 65.3%). Synaptic neural network weights and logistic regression parameters were used in a scoring model to predict the outcome of a single endoscopic injection of DxHA in 2 independent hospitals. An outcomes analysis using predictive models in independent clinics showed a good quality of prediction both with the use of logistic regression (75% and 90% of the correct prognosis) and using a neural network (89.7% and 77% of the correct prediction).Conclusion. An artificial neural network and a binary logistic regression model are an effective tool to assist urologists in identifying and applying endoscopic treatments for VUR in children.

Introduction. Nephrectomy (NE), heminephrectomy (HNE) and the formation of ipsilateral ureteroureteroanastomosis (UUA) do not exclude the possibility of preserving the distal ureter. The remaining ureteral stump can cause the formation of ureteral stump syndrome (USS) in the form of recurrent urinary tract infection (UTI), hematuria, pain syndrome, and stump empyema in some cases.Purpose of the study. To assess the incidence and treatment approach of USS in children after NE, HNE and UUA performed using open and laparoscopic access in different Russian clinics.Material and methods. The study is based on the results of treatment of 778 patients from 9 clinics in the Russian Federation and the Republic of Belarus in the period from 1998 to 2020. Patients underwent NE, HNE and UUA by open or laparoscopic access. The ureter was not removed completely, its stump was left. Open access was used in 313 (40.2%) children, laparoscopic in 465 (59.8%) cases. USS was detected in 27 (3.5%) patients. The ureteral stump was removed in 26 (96.3%) children. Open removal of the ureteral stump was performed in 11 (42.3%) patients, through laparoscopic access in 13 (50.0%) and vesicoscopically in 2 (7.7%) children.Results. There were 12 boys (44.4%) and 15 girls (55.6%) among the patients with USS. USS was detected on the right in 13 (48.1%) children, on the left - in 14 (51.9%). The median age of the patients was 25 [12; 42] months at the time of USS detection. Ureteral stump was sutured and ligated in 15 (55.6%) children during the primary operation, the stump was left open after excision in 4 (14.8%) children, it was not indicated how the stump was processed in 8 (29.6%) patients. Reflux to the stump was detected in 13 (48.1%) patients, USS against the background of obstruction was detected in 14 (51.9%) children. It was determined that the frequency of SCM is lower (9 (1.9%)) with the use of laparoscopic access than with open (18 (5.8%)) operations (p < 0.004). Clinical manifestations occurred in 85% of patients with USS within a year after surgery.Conclusion. USS is a rare complication (3.5% of cases) in patients who have undergone NE, HNE and UUA with the distal ureteric stump preserving. Performing these operations by laparoscopic access allows carrying out total ureterectomy and significantly reduces the likelihood of USS development.