The pathological features of renal and ureteral duplication anomalies in children are complex and diverse. One subset nvolves lesions at the lower end of a single ureter on the same side, including abnormal positioning of the upper renal-ureteric orifice, proximal ureteral dilation, as well as potential bladder-ureteral reflux (VUR) associated with the lower kidney. Clinically, this condition often presents with a series of symptoms such as hydronephrosis, uncontrolled urinary leakage during intervals, abdominal pain, recurrent urinary tract infections, and VUR. If timely medical intervention is not provided, it may further lead to renal scarring and renal function impairment[9]. Currently, there is no universally accepted standard for surgical strategies regarding pediatric renal duplication, with discussions primarily focusing on whether to excise or preserve the renal unit. Jordan et al.[10] pioneered laparoscopic heminephrectomy in 1993 as an innovative approach to treat renal and ureteral duplication anomalies in children. Despite its significant efficacy, heminephrectomy is considered the preferred option for managing poorly functioning or malformed duplicated kidneys, yet it comes with risks, particularly concerning the potential injury to normal renal tissues, leading to vascular damage, vasospasm, and even infection of the ureteral stump[11, 12]. Hence, surgical procedures must be executed with meticulous care. In recent years, treatment strategies for renal and ureteral duplication anomalies have seen a trend among experts favoring the preservation of the affected kidney to minimize potential negative impacts on renal function. Kidney-preserving surgeries include transurethral endoscopic ureteral dilation, ureteroureterostomy, single ureteral bladder reimplantation, and common sheath ureteral reimplantation (CSUR). The ureteral dilation procedure, noted for its minimally invasive characteristics, has emerged as an ideal choice for treating recurrent urinary tract infections, voiding dysfunction, and in younger patients who are unsuitable for heminephrectomy or complex urinary reconstruction, showcasing unique advantages. However, literature also reports suboptimal outcomes for ureteral dilation, with approximately 30% to 50% of cases experiencing VUR postoperatively, and between 42% to 100% of children requiring additional surgical interventions[13]. Furthermore, CSUR is commonly employed; this technique cleverly avoids the dissection of closely adjacent ureters, effectively reducing potential damage to the blood supply of the ureters. Nonetheless, the success of this procedure hinges on constructing a sufficiently long and wide submucosal tunnel in the bladder, which poses a significant challenge in younger children with smaller bladder volumes, as inadequate tunnel length may considerably increase the risk of postoperative VUR. Lee et al.[14] conducted a study revealing that among 39 children with renal duplication undergoing CSUR, despite a high rate of alleviation of upper urinary tract dilation at 92.3%, 17.9% still required secondary surgeries due to long-term complications. In light of these factors, pediatric surgeons have gradually decreased reliance on CSUR, shifting towards more reliable treatment options such as UU and UR.
The key to using ureteral reimplantation (UR) for treating renal duplication anomalies lies in the precise dissection of the upper and lower ureters within a common sheath, with particular attention to preserving the integrity of the normal ureters. Typically, dissection should extend only to the point where the two ureters share a wall, avoiding excessive separation that could impair the blood supply to the ureters. Common surgical techniques employed in UR include the modified Lich-Gregoir procedure performed extravesically and the Cohen and Politano-Leadbetter techniques performed intravesically, both of which have demonstrated high surgical success rates. However, in cases requiring the excision of ureteral dilation, the Cohen or Politano-Leadbetter procedures are often prioritized due to their specific technical advantages[15]. A study by Castagnetti et al.[16] indicated that UR treatment yielded satisfactory clinical outcomes for children with renal duplication, even in those with poor function of the upper kidney, showcasing significant efficacy. Nevertheless, the potential adverse effects of extensive lower urinary tract reconstruction surgeries performed during infancy on bladder function as the child grows warrant more attention and research[17]. In a cohort of 30 children who underwent UR, one case of acute urinary retention occurred post-catheter removal, possibly related to intraoperative damage to the distal ureter and the innervating nerves of the bladder muscular layer[18]. This condition was managed through catheterization, leading to a gradual return to normal urination after one week.
Foley first reported the use of ureteroureterostomy (UU) for treating renal and ureteral duplication anomalies in 1928[19]. In recent years, with advancements in minimally invasive techniques and accumulated experience, laparoscopic ureteroureterostomy (LUU) has demonstrated advantages over traditional open surgical approaches, such as reduced tissue trauma, ample working space, and confirmed efficacy. Gerwinn et al.[20] suggested that LUU is a safe and effective treatment for pediatric renal duplication, serving as a viable alternative to common sheath ureteral reimplantation (CSUR). Mcleod et al.[21] noted that the prognostic outcomes of LUU are independent of the partial renal function of the affected kidney and its ureteral diameter, reaffirming its safety and effectiveness. The author believes that compared to single ureteral bladder reimplantation, ureteroureterostomy can avoid vascular and nerve injuries associated with the opening of the bladder during reimplantation, while also preventing potential obstruction at the anastomosis site or vesicoureteral reflux (VUR) that may occur during the establishment of an anti-reflux mechanism through ureteral embedding.
The selection of the anastomosis site for LUU should be based on the surgeon's experience and preferences. The advantage of a proximal anastomosis lies in its ability to avoid excessive resection of the dilated ureter, as it only requires moderate adjustments at the anastomosis site, making it particularly suitable for severely tortuous and enlarged ureters. However, a potential risk is that if a stricture occurs postoperatively, subsequent surgeries may face challenges such as insufficient ureteral length or limitations in choosing the anastomosis site. Therefore, when dealing with mild to moderate dilation of the upper renal ureter, we prefer the distal horizontal anastomosis technique. This approach has a smaller anatomical scope, smooth operation, and does not require excessive resection of the diseased ureter, thus reducing surgical complexity and potential risks. Furthermore, distal anastomosis allows for more extensive excision of the duplicated ureter's residual stump, minimizing the risk of postoperative infection due to excess stump retention. During the anastomosis, a 6-0 absorbable suture is initially used to precisely stitch one needle at both the proximal and distal ureters for positioning. Subsequently, continuous suturing along the anterior and posterior edges of the ureter completes the end-to-side anastomosis, ensuring a tight and even junction. If necessary, a traction line may be placed through the abdominal wall to facilitate the lower renal ureter. Some surgeons also address the technical challenges posed by the narrower diameter of the recipient ureter by preemptively placing a D-J stent in the lower kidney under cystoscopy, followed by LUU after 2 to 4 weeks[9]. Gerwinn et al.[20] reported two cases (12.5%) of anastomotic leakage following LUU, with clinical presentations including febrile urinary tract infections and paralytic ileus. One case resolved with conservative treatment, while the other required percutaneous nephrostomy for recovery. In our study, among 35 children in the LUU group, there was only one case of anastomotic leakage, potentially linked to the surgeon's proficiency in laparoscopic pyeloplasty techniques. Regardless of the surgical approach employed, accurately identifying the duplicated ureters, meticulously ligating the upper ureter as distally as possible, selecting an appropriate anastomosis site, and avoiding ureteral twist and tension-free anastomosis are all critical factors for the success of the surgery.
LUU and UR aim to preserve upper renal function to the greatest extent; however, maintaining long-term function of the upper kidney may carry the risk of renal hypertension. Several studies have indicated that there is no clear causal relationship between the hypertension observed in these children and renal dysplasia of the upper kidney. Instead, renal scarring resulting from febrile urinary tract infections (UTIs) has been identified as one of the significant factors contributing to hypertension[22]. In our study, due to the relatively short follow-up period, no cases of hypertension have emerged, and further tracking is needed to determine whether renal hypertension complicates long-term outcomes. Furthermore, while some literature has mentioned the potential for "yo-yo reflux," where urine may flow from the donor ureter back into the recipient ureter following end-to-side anastomosis, raising concerns about an increased risk of recurrent infections in the recipient ureter and kidney, this theory has not received conclusive evidence in subsequent, more in-depth studies. From the data in this study, it appears that the diameter of the donor ureter has decreased to varying degrees postoperatively, with no significant dilation observed in the recipient ureter, indirectly suggesting that "yo-yo" reflux is not occurring.
In summary, both LUU and UR are effective surgical options for the treatment of complete renal and ureteral duplication anomalies in children. There are no significant differences between the two techniques regarding the number of stent placements, changes in the anteroposterior diameter of the affected upper renal pelvis before and after surgery, or improvements in differential renal function (DRF) of the affected kidney. Compared to UR, LUU is associated with shorter operative time, reduced intraoperative blood loss, and fewer postoperative hospital days. Additionally, since LUU does not involve the bladder, it results in less damage to the bladder in affected children, making it a procedure worth promoting in clinical practice.