Resumen: Objective: To analyze changes in the therapeutic approach at a tertiary care hospital following the implementation of a clinical guideline for the treatment of primary vesicoureteral reflux (VUR) in children. Population and methods: Retrospective study conducted in a cohort of patients with primary VUR (1989-2015) aged 0-15 years at a tertiary care hospital. The therapeutic approach before and after the development of the clinical guideline (2008) was compared. Results: A total of 297 patients (49.8% boys, 50.2% girls) were included; their mean age at the time of diagnosis was 21.71 months. VUR grading was: VUR I-III 45.1%, VUR IV-V 54, 9%; 124 were treated after the implementation of the clinical guideline (group 1), and 173, before (group 2). The mean follow-up period was 124.32 months. A conservative approach was the initial treatment in 70.3% of group 1 patients and 67.9% of group 2 patients. The number of surgeries remains constant (31.45% versus 31.79%), with an increase in the number of endoscopic surgeries (p< 0.005). The profile of patients has changed based on the application of the algorithm proposed by the guideline. Fewer surgeries were done in patients with VUR IV-V (82.32% versus 59.9%, p= 0.000) and there were fewer cases of kidney damage at diagnosis (49.4% versus 9.8%, p= 0.000). Conclusions: The implementation of the clinical guideline has favored an initially conservative approach in patients with severe grade VUR and nephropathy, for whom surgery was traditionally indicated initially. Using clinical guidelines favors a unanimous, evidence-based approach that reduces the performance of unnecessary invasive procedures. Idioma: Inglés DOI: 10.5546/aap.2017.eng.e362 Año: 2017 Publicado en: Archivos Argentinos de Pediatria 115, 6 (2017), e362-e369 ISSN: 0325-0075 Factor impacto JCR: 0.405 (2017) Categ. JCR: PEDIATRICS rank: 118 / 124 = 0.952 (2017) - Q4 - T3 Factor impacto SCIMAGO: 0.184 - Pediatrics, Perinatology and Child Health (Q3)