Beyond Reflux Grade: Long-Term Outcomes of Children with Grade 1 Vesicoureteral Reflux

Background: Grade 1 vesicoureteral reflux (VUR) is generally considered a low-risk condition and is commonly grouped with other low-grade reflux categories in the literature. Consequently, long-term outcome data specifically addressing Grade 1 VUR remain limited. We evaluated the long-term renal and infectious outcomes of children with Grade 1 VUR and characterized their principal associated clinical phenotypes. Methods: This retrospective cohort study included children diagnosed with Grade 1 VUR between 2008 and 2025 at a tertiary pediatric urology center. Primary outcomes were breakthrough urinary tract infection (UTI), proteinuria, and new renal scar formation. Principal associated clinical phenotypes and factors associated with adverse outcomes were evaluated using univariable analyses. Results: A total of 132 children with Grade 1 VUR involving 154 refluxing renal units were included. Median age at diagnosis was 6 years (IQR 4–9.25), and median follow-up was 8 years (IQR 5–9). A principal associated clinical phenotype was identified in all patients, most commonly voiding dysfunction (38.6%), recurrent UTI (28.0%), and renal anomalies (25.0%). Breakthrough UTI occurred in 46 patients (34.8%), proteinuria in 6 (4.5%), and new renal scar formation was identified in 7 of the 70 patients who underwent paired baseline and follow-up DMSA examinations performed according to clinical indications (10.0%). Renal adverse outcomes (proteinuria and/or new renal scar formation) were identified in 10 patients. Incident renal scarring was assessable only in the selectively imaged paired DMSA subgroup. Older age at diagnosis (p < 0.001) and abnormal baseline DMSA findings (80.0% vs. 41.8%, p = 0.040) were associated with renal adverse outcomes, while female sex was associated with breakthrough UTI (p = 0.009). Conclusions: In this tertiary referral cohort of children with Grade 1 VUR and associated clinical conditions, heterogeneous clinical outcomes were observed during long-term follow-up. These findings highlight the importance of interpreting Grade 1 VUR within the broader clinical context of the child; however, the independent contribution of reflux itself cannot be determined from the present study. These findings should therefore be regarded as descriptive and hypothesis-generating.