Diagnosing acute appendicitis in adults: Accuracy of color Doppler Sonography and MDCT compared with surgery and clinical follow-up

OBJECTIVE. The objective of our study was to evaluate the accuracy of color Doppler sonography and contrast-enhanced MDCT in the diagnosis of acute appendicitis in adults and their utility as a triage tool in lower abdominal pain. MATERIALS AND METHODS. We reviewed the medical records of 420 consecutive adult patients, 271 women and 149 men, 18 years old or older, referred from the emergency department to sonography examination for clinically suspected acute appendicitis between January 2003 and June 2006. Patients underwent sonography of the right upper abdomen and pelvis followed by graded compression and color Doppler sonography of the right lower quadrant. CT was performed in 132 patients due to inconclusive sonography findings or a discrepancy between the clinical diagnosis and the sonography diagnosis. Sonography and CT reports were compared with surgery or clinical follow-up as the reference standard. Statistical analyses were performed by Pearson's chi-square test and cross-tabulation software. RESULTS. Sonography and CT correctly diagnosed acute appendicitis in 66 of 75 patients and in 38 of 39 patients, respectively, and correctly denied acute appendicitis in 312 of 326 and in 92 of 92 patients. Sonography was inconclusive in 17 of 418 cases and CT, in one of 132 cases. Sonography and CT allowed alternative diagnoses in 82 and 42 patients, respectively. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for sonography were 74.2%, 97%, 88%, 93%, and 92%, respectively, and for CT, 100%, 98.9%, 97.4%, 100%, and 99%. CONCLUSION. Sonography should be the first imaging technique in adult patients for the diagnosis of acute appendicitis and triage of acute abdominal pain. CT should be used as a complementary study for selected cases.