Significance of Neutrophil-to-Lymphocyte Ratio as a Novel Indicator of Spontaneous Ureter Stone Passage

PURPOSE Stone size and location are generally considered the most important factors associated with spontaneous ureter stone passage (SSP). Several parameters related to inflammatory changes have been identified as predictors associated with SSP. Our aim was to investigate the predictive role of neutrophil-to-lymphocyte ratio (NLR) for SSP. MATERIALS AND METHODS A retrospective review was performed on 131 patients who were referred to the urology outpatient clinic and diagnosed with unilateral ureteral stones at our emergency department between July 2016 and December 2016. The presence of ureteral stones was confirmed with non-contrast-enhanced computed tomography (NCCT) for all patients. SSP was confirmed with either the patient collecting the stone during urination or by NCCT performed at 3 weeks from the first stone episode. Physical examination, urinalysis, complete blood count, serum chemistry and inflammatory markers, plain radiographs, and NCCT at initial presentation were reviewed to analyze predictors of future SSP. RESULTS Of 113 patients included for analysis, 90 (79.6%) passed their stones spontaneously. The SSP rates within 3 weeks according to the stone's size (5-10 mm and ≤5 mm) were 62.2% and 88.2%, respectively. A lower stone location [odds ratio (OR), 11.54; p=0.001], smaller stone size (≤5 mm) (OR, 8.16; p=0.001), and NLR (<2.3) (OR, 9.03; p=0.003) were independent predictors of SSP. CONCLUSION Low NLR (<2.3) may predict SSP in patients with ureter stones ×1.0 cm in size. Our results suggest that ureteral inflammation plays an important role in SSP. Early intervention may be considered for patients presenting with high NLR (≥2.3).