Complete duplication of the renal collecting system is a condition, when there are two ureters, that separately drainage into the bladder. This drainage is predicted by the Meyer-Weigert rule, in which the upper pole ureter drains inferomedially (orthotopic localization of the ostium), and the lower pole ureter drains superolaterally (ectopic localization of the ostium). In most cases we see upper pole obstructive uropathies, and the lower pole is refluxing. But there are rare exceptions to the law, when the lower pole drains inferomedially, and its ostium is ectopic.

The study aims 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 ureteroureteroanastomosis as an effective and safe method of surgical correction of the presented anomaly.

The patient is a five-month-old infant. In a neonatal period, the ultrasound study revealed a complete bilateral ureteral duplication. The patient had one episode of febrile urinary tract infection (acute pyelonephritis) and was treated by antibiotics. The voiding cystourethrogram didn't demonstrate any vesicoureteral refluxes (Fig. 1).

The intravenous urogram demonstrated a bilateral renal duplication and a left lower pole obstructive megaureter (Fig. 2). Cystoscopy was made, and two ostiums on the left and right side were seen. The ostium of the left lower pole ureter was hypoplastic and narrow, and insertion of a ureteral stent was impossible. 

In this case of massively dilated obstructed lower pole ureter and impossibility to insert the ureteric stent, it was decided to create a proximal ureteroureteroanastomosis using laparoscopic technic. The distal part of the lower pole ureter was dissected and crossed from the bladder. Then the proximal end-to-side ureteroureteroanastomosis was performed, using continuous suture (Vicryl 6.0). The ureteronephrostomic drainage was inserted through the lower pole ureter. The postoperative period was uneventful without any complications. The Foley catheter was removed on day 7 after the operation, and the ureteronehrostomic drainage was removed on day 10. 3 months after the operation, with control intravenous urography, the ureteroureteroanastomosis was well-functioning. The reverse development of megaureter and hydronephrosis was determined, the function of the lower segment of the duplicated left kidney was not impaired (Fig. 3).

Duplication of the collecting system forms in the case of development of two ureteral buds. Karl Weigert (1878) and Robert Meyer (1907) discovered the constant relationship between the upper (ectopic) and lower (orthotopic) pole ureters. During embryologic development, the kidneys and their ureters complete a 180-degree clockwise rotation (the ureters in their longitudinal axis). In cases of exception to the Meyer-Weigert rule the ureters go parallel, the upper pole ureter drains superolaterally, and the lower pole ureter drains inferomedially [1].

In multicenter studies showing heminephrectomy and ureteroureteroanastomosis for duplex kidney in children, no patients were identified with a violation of the Weigert-Meyer rule. In a study by Esposito et al. (2015), devoted to the use of heminephrectomy over a 5-year period, among 52 children there were no cases of violation of the rule mentioned [2]. In an article by Michaud et al. (2017), describing a comparison of heminephrectomy and ureteroureteroanastomosis for various pathologies of a duplex kidney, among 51 patients who underwent ureteroureteroanastomosis, there were no cases of violation of the Weigert-Meyer rule [3].

Only clinical cases have been reported in the literature on violations of the rule. And most of them are about adult patients. Darr et al. (2020) demonstrated the 23-year-old female patient with recurrent urinary tract infections and left sided sporadic flank pain for 3 years, who was diagnosed with an obstructive megaureter of the lower pole ureter. She underwent heminephrureterectomy because of the dysplastic lower pole [4].

Brown et al. (1988) presented the 30-year-old male patient with a fever and right hemiscrotal pain. He was diagnosed with a complete ureteral duplication with lower pole ectopia to the right epididymis. The ectopic ureter originated from the lower pole calix, so the patient was treated surgically, and the ureter was ligated in the scrotum [5]. The authors of this article proposed four embriological theories to explain the violation of the Meyer-Weigert rule: (1) the fusion of the supernumerary kidney to the inferior pole of a larger kidney; (2) the late appearance of a ureteral bud of a cranial end of the Wolffian duct; (3) the 180-degree rotation of the metanephric blastema; (4) the communication between two mesonephric structures at each end. But nowadays there isn't the single theory, which can explain such clinical findings.

Slaughenhoupt et al. (1997) reported a case of the 63-year-old male patient with hematuria, who was diagnosed with a complete ureteral duplication with the lower pole ectopia to the vas differens. The patient didn't want to undergo the surgical treatment [6].

Mishra et al. (2016) presented the 42-years-old male patient with an incarcerated inguinal hernia. Using computed tomography, the lower pole ectopia to the left hemiscrotum was found. He did not have any clinical signs of this pathology, so it was decided not to use surgical treatment [3].

Jain et al. (2008) demonstrated the 10-years-old male patient with periodic paraumbilical pain. He was diagnosed with a lower pole cystic dysplasia and a lower pole megaureter. The patient underwent heminephrectomy [7].

Stormont et al. (2020) reported a case similar to the one, demonstrated in our article. The newborn was diagnosed with a lower pole obstructive megaureter with the massively dilated lower pole ureter. The child underwent heminephrureterectomy [8].

There are not any articles about the ureteroureterostomy in cases of exceptions to the Meyer-Weigert rule, reported in the literature. Thus, our clinical case is the first one, that demonstrates the efficiency and safety of this method.

The Meyer-Weigert rule explains the constant relationship between two ureters in cases of complete duplication of the collecting system. The presented article demonstrates a clinical case of obstructive megaureter of the lower segment of a doubled kidney, which can be considered a violation of the Weigert-Meyer rule. In clinical practice, it is necessary to consider the possibility of such a phenomenon to determine the correct tactics for treating patients with this pathology.

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