Introduction. Anatomical features of the urinary tract in patients with duplicate kidneys are described using the Weigert-Meyer rule, since the orifice of the upper ureter has an ectopic location (inferomedial) and the orifice of the lower ureter has an orthotopic location (superolateral). However, there are rare cases of violation of this rule, complicated by obstructive megaureter, ectopic ureteral orifice, the presence of ureterocele.Objective. To report the rare clinical case of a lower pole obstructive megaureter as a violation of the Meyer-Weigert rule in the patient with complete ureteral duplication and to describe the use of ureteroureterostomy as an effective and safe method of surgical correction of the presented anomaly.Clinical case. We present a case of the infant (5 months old) with a lower pole obstructive megaureter. This pathology was identified through intravenous urography and voiding cystourethrography. Laparoscopic proximal end-to-side ureteroureteroanastomosis was chosen as a surgical treatment. Postoperative control intravenous urography showed the effectiveness (a reduction in the lower pole collecting system of the duplex kidney was revealed) and the safety of this method of correction.Conclusion.  There are only several clinical cases about exceptions to the Weigert-Meyer rule reported in literature, and most of them are about adult patients. The main surgical method of treatment in such cases is heminephrectomy. To our knowledge, this is the only reported case of using ureteroureterostomy in the patient with a lower pole obstructive megaureter. This technique has shown its effectiveness and safety for restoring the patency of the urinary tract, confirmed during the control postoperative examination.

Introduction. Kidney duplication is one of the most common urological developmental anomalies, the incidence of which is 0.8%. At the same time, various types of obstructive uropathy can be a concomitant pathology in such a situation. There are various methods for correcting obstructive uropathy. Currently, more and more often in the treatment of obstructive uropathy of one of the segments of the doubled kidney, a method such as ureteroureterostomy is used. However, there is still no consensus on which treatment tactics in this case is the most optimal. The aim of our work was to analyze literature about using ureteroureterostomy in patients with obstructive uropathies of a duplicated kidney, as well as to compare this technique with others. Materials and methods. Search results were analyzed in the scientific databases e-Library, PubMed, Medline, Web of Science, Embase, Cochrane Library and PEDro according to the following. keywords: «renal duplication», «heminephrectomy», «ureteroureterostomy», «obstructive uropathies». In total it was found 157 publications, after analyzing the literature, 33 papers were selected for review, most fully reflecting the topic. Results. Heminephrectomy is still popular for severely reduced or absent duplex kidney function, but it has complications such as decreased function of the remaining segment, pseudocyst formation, stump, urinoma, segmental hematoma, ureteral stricture, and vesicoureteral reflux into the remaining segment. Ureteroureterostomy, as an alternative method for correcting obstructive uropathies of a double kidney, has been recognized as effective and safe in many studies. Data are presented to prove that ureteroureterostomy is applicable for any function of the affected segment. In this article, various techniques for ureteroureterostomy are consecrated, from open intervention to robotic one. In addition, research data on the safety of ureteroureteroanastomosis in case of a pronounced discrepancy between the diameters of the ureters are presented. Among the complications of ureteroureteroanastomosis, cultitis, urine leakage in the anastomosis zone, urinoma, and stenosis of the anastomosis can be noted. The predictors of an unfavorable outcome of the proposed method were identified. These include ectopic ureterocele, hydronephrosis of both segments of the duplex kidney, as well as simultaneous ureteroureterostomy and reimplantation of the recipient ureter. Conclusions. Ureteroureterostomy in patients with various pathologies inherent in duplication of the kidney is an effective and safe technique that allows preserving the function of the segment and adequately draining it. The use of this technique does not depend on the presence of a decrease or lack of function of one of the segments.

Presentation of a rare clinical case of hydronephrosis of the lower half of the kidney due to vasoureteral conflict against the background of the complete doubling of the upper urinary tract. The rarity of this anomaly is demonstrated by only a single mention of a similar case in an adult patient in the literature. The patient, three years old, had dilatation of the upper urinary tract that was detected antenatally. According to the postnatal ultrasound results at three months, the anterior-posterior size of the pelvis of the lower half of the left kidney was 13 mm, and the parenchyma of the left kidney was 11 mm. The child was followed up on an outpatient basis. There were no laboratory or clinical manifestations of urinary tract infection. Ultrasound monitoring revealed progression of dilatation of the pelvis of the lower half max up to 40 mm and thinning of the kidney parenchyma in the projection of the lower pole up to 7 mm, in connection with which the child successfully underwent antevasal ureteropyeloanastomosis of the lower half of a completely doubled kidney. The anterior-posterior size of the pelvis of the lower half after removal of the pyelostomy was 16 mm. The child did not have any clinical and laboratory disease manifestations in the postoperative period. The described clinical case expands our understanding of the anatomy of obstruction of the pyeloureteral segment and hydronephrosis of the lower half of the duplex kidney. It enables us to plan surgical tactics, considering the possible intraoperative detection of the described anatomical configuration.