characterize the inter-rater reliability of VUR grade and UDR in children with VUR. METHODS: Voiding cystourethrograms (VCUG) of 20 pediatric patients (31 VUR-affected kidneys) were independently reviewed by four pediatric urologists in a blinded fashion. For each renal unit, grade was assigned according to the standardized international scale. UDR was calculated by dividing the largest ureteral diameter within the false pelvis by the distance between the L1-L3 vertebral bodies. The mean grade and mean UDR was calculated for each affected kidney. Corre- lation within each rater was determined using a Pearson’s correlation coefficient. Reliability of VUR grade and UDR was calculated using intraclass correlation coefficients (ICC) using a two-way ANOVA model interrater agreement. RESULTS: VUR grade (ICC ¼ 0.87, 95% CI ¼ 0.78-0.93) and UDR (ICC ¼ 0.95, 95% CI ¼ 0.92-0.97) were reliably measured by four independent raters. While UDR and grade were equally reliable measures, UDR had a tighter confidence interval. For each rater, grade and UDR were well-correlated (r ¼ 0.73-0.84; p <0.0001). In the upper ranges of measurements, grade was more variable than UDR [Figure]. Using an empirical threshold, the increased variability with grade may lead to significantly more differences in clinical decision-making among physicians (p ¼ 0.022). CONCLUSIONS: UDR has good inter-rater reliability among pediatric urologists. There was significantly more clinically relevant variability with grade than with UDR. Our study demonstrates that UDR is a more objective and reliable measure than grade, and may be a useful adjunct in clinical decision making and categorizing VUR. Source of Funding: none MP55-04 REVISITING THE ROLE OF GENDER ON EARLY DIAGNOSED PRIMARY VESICOURETERAL REFLUX IN INFANTS WITH PRENATAL HYDRONEPHROSIS Tomer Erlich*, Nathan Wong, Kizanee Jegatheeswaran, Melissa McGrath, Mandy Rickard, Bethany Easterbrook, Hamilton, Canada; Armando J Lorenzo, Toronto, Canada; Jacob Ramon, Yoram Mor, Tel-Hashomer, Israel; Luis H Braga, Hamilton, Canada INTRODUCTION AND OBJECTIVES: Vesicoureteral reflux (VUR) has been classically separated into 2 types. Mild (I-III) VUR has been found to be associated with normal kidneys and to affect predominately females. In contrast, severe (IV-V) VUR has been usually linked to renal abnormalities on imaging and considered as an almost exclusively male disorder. Herein, we examined the association between gender and VUR grade in infants with pre- natal hydronephrosis (HN), taking into account the presence of renal abnormalities, mode of presentation, development of UTI and HN grade. METHODS: Of 377 infants with prenatal HN <6 months at presentation who were prospectively entered in our database, 266 underwent voiding cystourethrogram (VCUG) at a mean time of 2.7 months, due to high (SFU III-IV) grade HN and presence of ureteral dilatation. Of these, 65 (22%) were found to have VUR with a mean age of 2.6+1.7 months and mean follow-up time of 19.9+16.9 months. The following VUR characteristics were analyzed according to gender: age at presentation, circumcision status, HN and VUR grade, presence of renal abnormalities on ultrasound (renal size discrepancies > 1cm) or DMSA (focal or diffuse defects or DRF<45%), UTI, mode of presentation (UTI vs. investigation of prenatal HN), reason for VCUG, continuous antibiotic prophylaxis (CAP) use and surgical indication. Comparative analyses between male and female gender for each VUR characteristic were performed with Fisher 0 s exact test. RESULTS: Of the 65 included infants, 41 (63.1%) were males, of whom 17 were circumcised (42%). Rates of UTI were 55% (36/65) and time to UTI was 8.7 + 12.8 months. Females were more likely to develop UTIs (75 vs. 44%, p<0.01). Renal abnormalities on DMSA and/ or ultrasound were present in 31 (48%) patients; 22 male (54%) infants vs. 9 females (38%) had renal abnormalities (p¼0.21). Grade I-III VUR (10 males vs. 4 females) was present in 14 patients (22%), while grade IV-V VUR was detected in 51 (78%) infants [31 males -75% of males with VUR vs. 20 females-83%; p¼0.55). Table 1A and B display a comparison of the aforementioned VUR characteristics according to gender. CONCLUSIONS: Contrary to previous studies, male gender was not shown to be a predictor of high grade VUR with renal abnor- malities on imaging studies in infants with prenatal HN. The two distinct VUR entities that have been previously reported require further inves- tigation. e736 THE JOURNAL OF UROLOGY â Vol. 195, No. 4S, Supplement, Sunday, May 8, 2016