Predictors of prolonged hospitalization and inflammation severity in acute appendicitis: a retrospective cohort study

Acute appendicitis remains one of the most common causes of acute abdomen and the leading indication for emergency abdominal surgery worldwide. Despite advances in imaging and clinical scoring systems, predicting disease severity and postoperative outcomes at the time of admission remains challenging. Early identification of patients at risk for complicated appendicitis or prolonged hospitalization may improve treatment planning and optimize resource utilization. This study evaluated the predictive value of routinely available inflammatory markers for complicated appendicitis and prolonged hospital length of stay.

This retrospective study included adult patients who underwent emergency appendectomy for acute appendicitis between May 2024 and April 2025. Demographic characteristics, hospital length of stay, surgical and pathological findings, and admission laboratory parameters were analyzed. Total white blood cell count (WBC-T), C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), and left shift (LS) were assessed. Disease severity was classified according to the American Association for the Surgery of Trauma (AAST) grading system and categorized as uncomplicated or complicated. Hospital stay was classified as regular (≤2 days) or prolonged (>2 days). Independent predictors were identified using univariate and multivariate logistic regression analyses. Receiver operating characteristic (ROC) analysis and the Youden index were used to determine optimal cut-off values.

A total of 387 patients were included; 24.8% experienced a prolonged hospital stay, and 15.0% had complicated appendicitis. CRP, NLR, and LS were significantly higher in patients with prolonged hospitalization, whereas WBC-T was not. Multivariate analysis identified elevated CRP as the only independent predictor of prolonged hospital stay (odds ratio [OR]: 1.014, 95% confidence interval [CI]: 1.010-1.019; p<0.001). A CRP cut-off value of 43.05 mg/L predicted prolonged hospitalization with 59.4% sensitivity and 79.4% specificity (area under the curve [AUC]: 0.728). For complicated appendicitis, elevated CRP (OR: 1.008, 95% CI: 1.005-1.012; p<0.001) and increased LS (OR: 1.049, 95% CI: 1.012-1.087; p=0.008) were independent predictors. A CRP cut-off of 27.46 mg/L predicted complicated appendicitis with 69% sensitivity and 67% specificity (AUC: 0.74), whereas an LS cut-off of 77.61% demonstrated high sensitivity but limited specificity.

Admission CRP is a practical and reliable biomarker for predicting both prolonged hospitalization and complicated appendicitis. Combined assessment of CRP and left shift may further improve preoperative risk stratification and support clinical decision-making.