Neutrophil:Lymphocyte Ratio as a Predictive Factor for Success of Nephron-Sparing Procedures in Patients with Emphysematous Pyelonephritis.

Introduction: We studied the value of neutrophil:lymphocyte ratio (NLR) in predicting the success of nephron-sparing procedures in management of emphysematous pyelonephritis.

Methods: In this single-center retrospective study, patients underwent nephron-sparing procedures between 2007 and 2014. Severity was graded by Huang-Tseng classification. Thrombocytopenia, acute renal failure (ARF), shock, altered sensorium, and admission NLR were evaluated for predictive value for successful outcomes. Receiver operating characteristic curves were plotted to determine optimal cutoff of NLR for differentiating successful and unsuccessful outcomes. Two-sided p values were calculated with the χ test. Factors that were significant on univariate analysis were combined in a model with NLR.

Results: Sixteen patients, 14 (87.5%) of whom were female and 14 (87.5%) of whom had diabetes, were included. Ten (63%) had severe emphysematous pyelonephritis. The optimal cutoff of NLR was 5. Four (44%) of 9 patients with NLR above 5 had unfavorable outcomes compared with none of 7 with NLR of 5 or less, giving a risk ratio of 1.8 (95% confidence interval [CI]= 1.01-3.22, p = 0.0417). Area under the curve for NLR alone was 0.77 (95% CI = 0.55-0.99, p = 0.014). High NLR and ARF were the only factors predicting unsuccessful outcome (p = 0.0417 each). When these were combined in a model (NLR as continuous variable), the area under the curve increased to 0.92.

Conclusion: NLR is a useful predictive marker in emphysematous pyelonephritis. Its predictive value increases when combined with presence or absence of ARF. In patients with high NLR and ARF, the threshold for considering nephrectomy should be low.