Introduction: Delayed or wrong diagnosis in patients with appendicitis can result in perforation and consequently increased morbidity and mortality. Serum total bilirubin may be a useful marker for appendiceal perforation. The aim of this study was to determine and compare pre-operative total bilirubin level and other diagnostic tools (patient age, duration of symptoms, Alvarado score, white blood cell, C-reactive protein, ultrasound and contrast enchanced CT scan) in cases of acute appendicitis in order to improve the clinical decision making. Materialsand methods: We identified 102 patient with acute appendicitis after excluding those with other causes of hyperbilirubinemia among the 180 patients that underwent a laparoscopic or an open appendectomy from June, 2011 to March, 2015 in UB Songdo Private Hospital. These cases were also subjected to liver function tests and clinical diagnosis was confirmed perioperatively and postoperatively by histopathological examination. According to histological results, these cases were classified two groups: positive(acute appendicitis with perforation and/or gangrene) and negative(acute appendicitis without perforation or gangrene). Their clinical and investigative data were compiled and analyzed. Statistical analysis was performed using independent sample t test, Chi square test, and direct logistic regression. The level of significance was set at P< 0.05. Results: Serum total bilirubin was found to be significantly increased(1,5mg/dL) in case of negative group and much higher (3,6mg/dL) in cases of positive group (P <0.001). The level of total bilirubin was higher than 3 mg/dL in cases of gangrenous/ perforated appendicitis while in cases with acute appendicitis it was lower than 3 mg/ dL. Also Alvarado score (P <0.01), C-reactive protein (P <0.001) and contrast enchanced CT scan (P <0.05) were statistically significant diagnostic tools for acute appendicitis. Conclusion: Assessment of preoperative total bilirubin is useful for the differential diagnosis of gangrenous/perforated appendicitis.