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.
The study of 420 medical records found that sonography correctly denied acute appendicitis in 303 of 312 adult patients, meaning it had a 97% specificity rate, said Diana Gaitini, MD, of Rambam Health Care Campus in Haifa, Israel. "When the patient does not have acute appendicitis, the negative result of the color Doppler ultrasound examination is highly confident," she said. On the other hand, ultrasound's sensitivity rate was 74%, meaning it missed the diagnosis in 23 of 89 patients, Dr. Gaitini said. Ultrasound was inconclusive in 17 patients.
"We performed CT in 132 patients because the ultrasound examination was inconclusive or the patient was showing classical signs and symptoms of acute appendicitis even though the ultrasound examination was negative," said Dr. Gaitini. CT correctly diagnosed acute appendicitis in 38 of 39 patients (99% sensitivity rate) and correctly denied acute appendicitis in all 92 patients (100% specificity rate), said Dr. Gaitini. CT was inconclusive in one patient.
"CT has a slightly higher specificity rate and a higher sensitivity rate than ultrasound, but ultrasound can help the radiologist make a definitive diagnosis in most patients," Dr. Gaitini said. "The higher diagnostic performances of CT need to be evaluated against its disadvantages. Lack of radiation exposure (which is especially important in a population of mostly young patients), higher availability, lower cost and high specificity of color Doppler ultrasound are the main reasons for trying ultrasound first," she said.
The study appears in the May issue of the American Journal of Roentgenology.
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