CRP and Ascites: In model 1 (variables selected through backward elimination), a CRP level of 3.0–5.9 mg/dL (OR: 3.58, 95% CI 1.33–9.59, P = 0.0114) and ≥ 6.0 mg/dL (OR: 11.61, 95% CI 4.95–27.21, P < 0.0001), grade 1 FS (OR: 4.26, 95% CI 1.08–16.74, P = 0.0381), grade 2 FS (OR: 6.02, 95% CI 1.56–22.78, P = 0.0083), grade 3 FS (OR: 18.44, 95% CI 4.70–72.36, P < 0.0001), appendicolith (OR: 2.94, 95% CI 1.43–6.03, P = 0.0179), ascites (OR: 2.68, 95% CI 1.19–6.07, P = 0.0032) strongly predicted complicated acute appendicitis.