CRP and metabolic acidosis: In addition, the bootstrap-based feature selection stability analysis showed that all 13 predictors were re-selected by LASSO in at least 92.5% of 200 bootstrap resamples (range: 92.5–100%), with lactic acid, C-reactive protein, neutrophil percentage, abdominal distension, peritoneal irritation signs, and metabolic acidosis being selected in 100% of resamples, supporting the stability of the final feature set.