Introduction: Acute appendicitis is the most common explanation for acute abdomen presentation. CT scan is modality of choice in diagnosis of acute appendicitis and differentiates it from the other case of acute abdomen. This study evaluates accuracy of CT scan in differentiation complicated and non complicated appendicitis. Methods: our study is a retrospective study performed on 94 patients who underwent appendectomy in Firuzgar Hospital within a period of 2 years in 2016-2018. These patients examined by CT scan within 48 hr before surgery. CT scan evaluated by an expert radiologist and CT scan data compared with pathological results. Diagnosis of complicated appendicitis was performed base on one of five CT scan findings: abscess, phlegmon, extra luminal air, extra luminal appendicolith, focal defect in the appendiceal wall. In pathological results perforated and nonperforated gangrenous appendicitis classified as complicated appendicitis.Results: 33% and 67% of patients were female and male respectively .mean age of population was 36.5 years .sensitivity and specificity of CT scan in diagnosis of acute appendicitis were 100% and 78% respectively. This study showed the sensitivity and specificity and accuracy of CT scan in diagnosis of complicated appendicitis were 71%, 94%, 89% respectively.Conclusion: same of previous study, this study showed high sensitivity and specificity in diagnosis of acute appendicitis and also showed high specificity in diagnosis of complicated appendicitis. In present study, the sensitivity of CT scan in diagnosis of complicated appendicitis is lower than previous studies probably because gangrenous non perforated appendicitis cases didn’t have prominent finding in CT scan for differentiation from non gangrenous non perforated appendicitis (non complicated appendicitis).
