Endoscopic subureteric injection (STING) stands out as a widely used, reliable and effective minimally invasive surgical technique in the treatment of vesicoureteral reflux (VUR). The success rate of STING has been reported to be related to some factors such as reflux grade, surgical technique, ureteral orifice anatomical abnormalities and other complicating factors such as lower urinary tract dysfunction (LUTD). Interestingly, there are different reports regarding the effect of LUTD on subureteric injection success. Some studies have shown that no difference in the success rate of STING between the presence and absence of voiding dysfunction (1, 2). On the contrary, it is emphasized in the AUA Vesicoureteral Reflux Guideline that the success of STING decreases in VUR accompanied by bladder-bowel dysfunction. Although the direct contribution of LUTD to the formation of VUR is still unclear, its presence is known to increase urinary tract infection (UTI), renal scarring and to reduce spontaneous resolution (SR) rates (3). Therefore, the EAU Paediatric Urology Guidelines recommends that if children with VUR exhibit lower urinary tract (LUT) symptoms, they should undergo an evaluation, and treated if LUTD is detected. To our knowledge, no study specifically focuses on objective LUT parameters as a factor in the success of STING. We aimed to study the presence of lower urinary tract dysfunction (LUTD) and those objective parameters obtained from voiding diary (VD), uroflowmetric (UF) and postvoiding residual urine (PVR) and voiding dysfunction symptom score (VDSS) as possible factors affecting the success rate on STING to correct VUR.

Children who underwent STING for the first time due to low (I-II) and moderate (III) grade of VUR in our clinic between 2012 and 2022 were included. All records were evaluated retrospectively. All children diagnosed with VUR were routinely evaluated for LUTD with VD, UF, PVR and Voiding Dysfunction Symptom Score (VDSS). STING was performed with dextranomer/hyaluronic acid copolymer paste under general anesthesia by a pediatric cystoscope when the urine culture was sterile. All children underwent control VCUG at the 6th postoperative month. In this study, each system with VUR was accepted a renal unit (RU). RUs were divided into two groups according to the presence of postoperative VUR: Group 1, those with no VUR (successful), and Group 2, those with unresolved VUR (failure). Demographic characteristics, DMSA scintigraphy findings and voiding parameters (voiding frequency and urgency/incontinence in VD, maximum flow rate (Qmax), flow pattern (normal/ abnormal), maximum bladder capacity (MBC)/expected bladder capacity (EBC) in UF and VDSS) were compared between the two groups.

A total of 80 children (73 (91.3%) girl, 7 (8.8%) boy) with a median age of 8 (3-16) years were included in the study.  There is a total of 112 RUs, 48 of which are unilateral and 32 bilateral. 48 (60%) children had unilateral VUR, and 32 (40%) bilateral VUR. 38 (33.9%) grade 1 VUR, 39 (34.8%) grade 2 and 35 (31.3%) grade 3 were detected. Of the children with Grade 1 VUR, 29 (76.3%) had febrile UTI, 26 (68.4%) had abnormal DMSA findings, and 22 (57.9%) were bilateral.  VUR was not detected in control VCUG following STING procedure in 93 (83%) of 112 RUs (group 1: 93 RUs), (group 2: 19 RUs). Febrile UTI, constipation, VUR phase, VUR grade, abnormal DMSA findings, abnormal UF pattern, and urinary incontinence in VD were similar between the two groups. No difference was found between those groups in terms of daytime voiding frequency, Qmax, MBC/EBC, PVR and VDSS (Table 1).

In the AUA VUR guideline published in 2017, it was reported that the reflux resolution rate after endoscopic surgery was 89% in children without LUTD, but this rate decreased to 50% if accompanied by LUTD. Despite the guideline-based experience, there are some studies reports conflicting results. In a study evaluating 54 children with high-grade VUR and bladder dysfunction as a subgroup, it was reported that a cure rate of 83% was achieved after 1 to 3 endoscopic interventions. The authors concluded that bladder dysfunction is not a contraindication of STING [2]. In another study including 200 children aged between 2 and 15, it was found that the presence of LUTD increased the failure of endoscopic surgery by 2.493 times [3]. 
In our retrospective study, children who underwent endoscopic intervention for low-moderate VUR were evaluated, and no difference was found in objective LUT parameters between successful and failed STING groups. The present study stands out in terms of comparing parameters such as flow pattern and rate, bladder capacity, symptom score and PRV between groups for the first time according to the results of STING unlike other published studies evaluated based solely on the diagnosis of LUTD.

In the present series, which was homogeneous in terms of age, VUR grade, renal cortical damage, surgical technique, and volume of injected material, it was found that there was no difference in preoperative parameters of VD, UF, PVR and VDSS between successful and failed endoscopic correction.  Therefore, we believe that effectively treated preoperative LUTD provides a comparable STING success rate for correcting low to moderate-grade vesicoureteral reflux (VUR) in the short term.

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