Diagnostic value of systemic immune-inflammation index in differentiating testicular torsion from epididymo-orchitis based on symptom duration: A retrospective observational study

Acute scrotal pain, most commonly caused by testicular torsion or epididymo-orchitis, requires rapid differentiation to preserve testicular viability, particularly within the early hours of symptom onset. The systemic immune-inflammation index (SII), derived from platelet, neutrophil, and lymphocyte counts, has emerged as a potential biomarker in inflammatory conditions. In this retrospective study, a total of 283 patients presenting with acute scrotal pain between January 2012 and May 2025 were analyzed, including 139 patients with testicular torsion and 144 with epididymo-orchitis. Demographic characteristics, symptom duration, and complete blood count parameters were evaluated, and neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and SII were calculated. Patients were stratified according to symptom duration (≤ 6 hours vs > 6 hours), and intergroup comparisons were performed. SII, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and mean platelet volume levels were significantly higher in patients with testicular torsion (all P  < .05). Multivariate logistic regression analysis identified SII, mean platelet volume, and C-reactive protein levels as independent predictors of testicular torsion ( P  < .05). Among patients presenting within 6 hours of symptom onset, SII demonstrated acceptable discriminative ability, with an optimal cutoff value of 830 (area under the curve: 0.737), yielding 72.0% sensitivity and 75.4% specificity. These findings suggest that SII may serve as a readily available adjunctive biomarker for the early differentiation of testicular torsion from epididymo-orchitis, particularly within the critical 6-hour window. Although not sufficient as a standalone diagnostic tool, its integration with clinical and imaging findings may improve early diagnostic accuracy, and further prospective multicenter studies are warranted to validate these results.