BACKGROUND Acute appendicitis (AA) is one of the commonest causes of acute abdominal emergencies. Accurate diagnosis and earlier surgery is imperative in such cases. Ultrasonography (US), and computed tomography (CT), are main stays accurate diagnosis of this disease. This study was conducted to compare the accuracy of US and CT in the diagnosis of AA and reduce number of negative appendectomies. METHODS This prospective study was done after approval from institutional ethical committee and obtaining written consent. 164 patients with clinical features suggestive of AA, were selected from emergency department of Patna Medical College, Patna India during the period from January 2019 to December 2020. 98 were males and 66 females, mean age being 18.08 years. 142 patents (86.58 %) underwent surgery, and 22 patients (13.41 %) were kept on clinical observation in hospital after imaging. After detailed clinical workup and laboratory investigations, all patients were subjected to both US and CT examination. Each patient was reevaluated clinically, and a clinical correlation was done between both sets of results. Based on these, final decision was made. Accuracy was decided based on intra-operative findings in appendectomy group and were correlated with imaging findings later with histopathologic findings. RESULTS Males outnumbered females, abdominal pain was present in 100%. The sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of US in diagnosis of AA in our study were 92.6 %, 76.4 %, 95.3%, 71.0% and 88.9 % respectively. The sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of CT in diagnosis of AA were 99.1 %, 90.5 %, 98.6%, 87.8% and 97.8 % respectively. CONCLUSIONS US should be the first-line imaging modality as it is free from radiation. CT is recommended as additional imaging tool to raise accuracy in diagnosis except in pregnancy and selected pediatric patients. KEYWORDS Acute Appendicitis, Computed Tomography, Ultrasound

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