Preoperative differentiation of acute appendicitis using NLR, SII, and maximum appendiceal diameter: a retrospective single-center diagnostic study

Background Rapid classification on Accurate preoperative differentiation between uncomplicated (UCAA) and complicated acute appendicitis (CAA) is essential for guiding treatment but remains challenging. Existing tools, such as clinical scores and common inflammatory markers, lack sufficient accuracy for reliable stratification. Methods In this retrospective single-center study, 207 patients with pathologically confirmed appendicitis (52 UCAA, 155 CAA) undergoing laparoscopic appendectomy between June 2024 and September 2025 were analyzed. Multivariate logistic regression and ROC curve analyses were performed. Results Individual AUCs were 0.863 for NLR (cut-off 5.22), 0.803 for SII (cut-off 1292.3), and 0.815 for maximum appendiceal diameter (cut-off 10.5 mm). Their combination achieved a superior AUC of 0.891 (95% CI: 0.840–0.942), with 86.54% sensitivity and 80.65% specificity. NLR and maximum appendiceal diameter were independent predictors of CAA. Conclusion The combination of NLR, SII, and maximum appendiceal diameter improves preoperative diagnostic accuracy for acute appendicitis over single parameters, potentially aiding individualized treatment planning and reducing diagnostic uncertainty.