The relationship between subureteric tunnel length, bladder wall thickness and distal ureter diameter measured by ultrasonography before subureteric injection with treatment success in children whose vesicoureteral reflux

The aim of this study was to evaluate the relationship between subureteric tunnel length (detrusor entry-orifice distance), bladder wall thickness and distal ureter diameter measured by ultrasonography (USG) before subureteric injection in children with primary vesicoureteral reflux (VUR) with treatment success. Thirty-five patients (53 renal units) between the ages of 1 to 16 who underwent subureteric injection due to primary VUR between 2020-2022 were included in our study. Prospectively collected data were evaluated retrospectively. The wall thickness of the bladder at the ureteral orifice, the length of the subureteric tunnel and the distal diameter of the ureter were measured by USG and recorded as "mm" before the surgery. At the same time, age, gender, degree of VUR, side, bilaterality, degree of hydronephrosis, complaints of admission, bladder-intestinal dysfunction, renal scar signs were recorded. The effect of these data on the success of treatment was evaluated. The mean age of the patients was calculated as 6.83 ± 3.84 years. 32 of patients (%91,4) were girls and three patients (%8.6) were boys. Reflux was on the right in 6 (17.1%) patients, on the left in 11 (31.4%), and bilateral in 18 (51.4%). On the right side grade 3 reflux was more common (25.7%) and on the left side grade 4 reflux was more common (34.3%). The overall success of the operation was calculated as 79% (n=42/53). There were no statistically significant differences between unsuccessful and successful groups in terms of age, gender, degree of VUR, side, bilaterality, degree of hydronephrosis, complaint of admission, bladder-intestinal dysfunction, bladder wall thickness and distal ureter diameter (p>0.05). In the successful group, 16 patients (%38.1) had renal scars, while in the unsuccessful group,10 patients (%90.9) had renal scars. A statistically significant difference was found between the successful and unsuccessful groups in terms of the presence of renal scars (p=0.002). The mean detrusor-orifice distance was measured as 7.32 ± 3.15 mm in the unsuccessful group and 10.64 ± 3.78 mm in the successful group. A statistically significant difference was found between both groups (p=0.004). The ratio of the detrusor-orifice distance to the distal diameter of the ureter (D/U ratio) was calculated as an average of 1.37±0.45 in the unsuccessful group, while in the successful group it was calculated as 2.12±0.83. It was observed that this ratio was significantly lower in the unsuccessful group compared to the successful group (p=0.006). The probability of failure was estimated as 81.82% (95% CI=48.2-97.7) for those with a detrusor orifice entry distance <7.4 mm, and the probability of success was estimated as 80.95% (95% CI=65.9-91.4) for those above this value. In order to predict the success of endoscopic injection treatment of VUR, to inform the patient's parents accordingly and to decide on the appropriate treatment method, the detrusor-orifice distance and the D/U ratio measured by USG are reliable parameters. Key Words: Vesicoureteral reflux, Subureteric tunnel, Endoscopic injection