Neutrophil-to-lymphocyte ratio as a predictor of primary vesicoureteral reflux evolution in children with associated acute pyelonephritis.

Background: Neutrophil-to-lymphocyte ratio (NLR) has been recently postulated as an inflammatory biomarker for the diagnosis of vesicoureteral reflux (VUR). The aim of this study is to determine the role of NLR as a predictor of evolution of primary VUR in patients with associated acute pyelonephritis (APN).

Methods: A retrospective observational cohort study was performed in patients with APN episodes with associated primary VUR diagnosed between 2013-2020. Patients were divided into two groups according to VUR evolution after APN: group A [spontaneous resolution (SR)] and group B [VUR complications development (CD) during follow-up: new APN or renal function worsening]. Demographic, prenatal, laboratory, microbiological and radiological data were analysed. Sensitivity and specificity for CD of VUR was determined by receiver operating characteristic (ROC) curves.

Results: A total of 1,146 episodes of APN were analysed of which 273 patients with APN and associated primary VUR were finally included (median age of 11 months at APN diagnosis). SR of VUR occurred in 169 patients (SR group), while CD were observed in the remaining 104 patients (CD group). No differences in demographic, prenatal, microbiological and radiological features were observed. CD patients had significantly higher levels of leukocytes, neutrophils, NLR, C-reactive protein and creatinine. NLR was the parameter with the highest area under the curve (AUC =0.966) for predicting the development of VUR complications (cut-off point =3.41) with a maximum sensitivity of 92.7% and specificity of 91.1% (P<0.001).

Conclusions: NLR may be considered as a simple and cost-effective predictor of clinical outcome of VUR, which may correlate with the increased risk of developing complications of primary VUR after an episode of APN. Therefore, it should be included in the management algorithm for these patients, although future prospective studies are still required to confirm these results.