Routine Metabolic and Inflammatory Biomarkers as Predictors of Renal Recovery Following Outpatient Treatment of Urinary Tract Infection

Objective: Urinary tract infection (UTI) can cause transient deterioration of renal function, particularly in patients with comorbidities. Although renal function often improves after successful treatment, factors predicting recovery remain unclear. This study investigated the association between routine metabolic and inflammatory biomarkers and renal recovery following outpatient UTI treatment.Methods: This retrospective single-center cohort study included adult outpatients diagnosed with UTI (January 2022–June 2023). Demographic, clinical, and laboratory parameters—including glycated hemoglobin (HbA1c), thyroid-stimulating hormone (TSH), vitamin B12, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and aggregate index of systemic inflammation (AISI)—were collected. Renal recovery was defined as an increase in estimated glomerular filtration rate (eGFR) at the first post-treatment follow-up. A secondary sensitivity analysis applied a stricter threshold (≥10% or ≥10 mL/min/1.73m² increase). Multivariable logistic regression and ROC curve analyses were utilized.Results: Of 146 patients, 84 (57.5%) demonstrated renal recovery under the primary definition. In multivariable analyses adjusted for clinical confounders and baseline eGFR, lower baseline NLR (OR 0.470, p=0.005) and PLR (OR 0.661, p=0.044) emerged as independent predictors of renal recovery. However, in the sensitivity analysis defining major clinical recovery, all inflammatory biomarkers lost their statistical significance. Furthermore, ROC analyses indicated poor standalone discriminative accuracy for all biomarkers individually (AUC < 0.60).Conclusion: When adjusted for initial renal reserve, lower NLR and PLR act as independent predictors of modest renal recovery after outpatient UTI treatment. However, they cannot predict major functional improvement and show poor standalone discriminative accuracy. Therefore, these routine biomarkers should complement comprehensive clinical assessment rather than serve as isolated prognostic tools.