Are the Preoperative Systemic Immune-Inflammation (SII) Index and Hematological Inflammatory Parameters Predictors for Systemic Inflammatory Response Syndrome (SIRS) After Retrograde Intrarenal Surgery (RIRS)?

Objective: The study aimed to evaluate whether there is a relationship between the preoperative values of the platelet lymphocyte ratio (PLR), the neutrophil lymphocyte ratio (NLR), and systemic immune inflammation (SII) index and the development of systemic inflammatory response syndrome (SIRS) in patients undergoing retrograde intrarenal surgery (RIRS) for kidney stones. Material and Methods: Demographic and laboratory data of patients who underwent RIRS were collected. NLR, PLR, and SII indices were obtained from the complete blood count parameters. Stone characteristics were obtained from preoperative non-contrast computed tomography. Univariate and multivariate analyses were performed to identify risk factors of SIRS. Results: SIRS was detected in 27 (3.6%) of 748 patients included in the study. Stone volume, Hb level, operation time, and SII index were independent risk factors in predicting SIRS. The established threshold for predicting SIRS based on stone volume is 1589 mm³, demonstrating a sensitivity of 88.9%, specificity of 70.0%, and an area under the curve (AUC) of 0.863. The hemoglobin level cut-off is 14.9 g/dl, with a sensitivity of 96.3%, specificity of 56.0%, and AUC of 0.198. The SII index threshold is 703, yielding a sensitivity of 81.5%, specificity of 73.5%, and AUC of 0.820. The operation time cut-off is 62.5 minutes, showing a sensitivity of 88.3%, specificity of 93.3%, and AUC of 0.967. Conclusion: The SII index appears to be an independent, easily accessible, and cost-effective predictor for SIRS following RIRS.