DIAGNOSTIC ACCURACY OF ULTRASONOGRAPHY IN COMPARISON WITH COMPUTED TOMOGRAPHY IN DIAGNOSING ACUTE APPENDICITIS

BACKGROUND Studies regarding accuracy of Ultrasonography and Computed Tomography for diagnosis of appendicitis is not frequently done after the advancement in ultrasonography instrumentation. Imaging studies evolves rapidly due to advancement in technology. It is mandatory to update imaging methods for various pathologies. Aims and Objectives-To assess and compare accuracy of Ultrasonography and Computed Tomography to diagnose acute appendicitis in patients with suspected acute appendicitis. MATERIALS AND METHODS Study Type-Descriptive study for diagnostic accuracy. Between January 2014 and January 2016, 400 patients who presented to emergency department with high clinical suspicion of appendicitis were evaluated with Ultrasonography and Computed Tomography. Computed Tomography examinations were performed with a sixteen-slice helical CT scanner (GE, Brivo, 385 series) by means of a rapid thin-scanning technique. For the Ultrasonography examinations, we used 5 to 11 MHz linear array, 3 to 6 MHz curved array (GE-Voluson S6). Curved array transducers were used in obese patients to allow deeper penetration. Ultrasonography examinations were performed using the graded compression technique described by Puylaert.([1,2]) The Computed Tomography and Ultrasonography examinations were evaluated separately within 1 hour by two radiologists who were unaware of the findings on the other examination. The surgeon was not informed about the radiologic diagnosis. The surgeon decides further management in these patients based on clinical and laboratory data. The diagnosis of acute appendicitis at surgery was established based on macroscopic findings. A macroscopically normal appendix at laparoscopy was left intact. A normal looking appendix at laparotomy by a split-muscle incision was excised. All excised appendix was microscopically analysed by histology using paraffin sections for final diagnosis of acute appendicitis. All data underwent statistical analysis using the McNemar test. The study protocol was approved by the hospital's ethical committee for human studies. RESULTS The sensitivity of Ultrasonography and Computed Tomography was 95% and 93% respectively, and the specificity was 82% and 75% respectively. The positive predictive value was 91% and 87% respectively, and the negative predictive value was 90% and 85% respectively. The accuracy of Ultrasonography was 91% and CT was 87% respectively. Based on the McNemar test results, the calculated 'p' value for sensitivity, specificity and accuracy was not less than 0.05, which indicates that CT was not superior to Ultrasonography in the diagnosis of acute appendicitis. On comparing Z = 1.43 it is less than the level of significance value, i.e. 1.96, therefore not significant which concludes that Computed Tomography is not superior to Ultrasonography for diagnosing acute appendicitis. CONCLUSION USG for the diagnosis of acute appendicitis has accuracy same as that of Computed Tomography. Wall pattern and wall thickness is better studied with USG. Further studies are needed to compare wall thickness and wall pattern by USG and CT to conclude which modality is better for diagnosing acute appendicitis.