Predictors of grade 3–5 vesicoureteral reflux in infants ≤ 2 months of age with pyelonephritis

Background: This study aimed to assess predictors for grade 3–5 vesicoureteral reflux (VUR) in infants ≤ 2 months of age admitted for first urinary tract infection (UTI). Methods: Retrospective cohort study of 195 infants ≤ 2 months admitted to a pediatric ward for first UTI between 2006 and 2017. Clinical, laboratory, and imaging data were collected from electronic medical charts. We examined associations between grade 3–5 VUR and different patient characteristics. Results: Twenty infants (10%) were diagnosed with grade 3–5 VUR; all had fever. Infants with grade 3–5 VUR had higher blood neutrophil percentage (BNP) (65% vs. 46%, P < 0.001), higher neutrophil-to-lymphocyte ratio (NLR) (2.6 vs. 1.3, P < 0.001), more renal ultrasound abnormalities (prenatal 26% vs. 5%, P = 0.007; postnatal 84% vs. 55%, P = 0.015), and Pseudomonas UTI (15% vs. 1%, respectively, P < 0.001). NLR > 1.65 showed sensitivity 100% and specificity 61% for detecting grade 3–5 VUR. BNP > 53% showed sensitivity 100% and specificity 60% for detecting grade 3–5 VUR. BNP was the best single marker for grade 3–5 VUR with area under the curve (AUC) of 0.82 (95% CI 0.75–0.89). In a multivariate model, AUC for combination of BNP and hydronephrosis was 0.86 (95% CI 0.79–0.93, P = 0.007). Conclusions: Infants ≤ 2 months of age admitted for a first UTI are at risk for grade 3–5 VUR and thus should undergo a voiding cystourethrography (VCUG) if their renal ultrasound is abnormal or if they have Pseudomonas UTI. Avoiding VCUG can be considered in afebrile infants and in infants with BNP < 53% or NLR < 1.65.