Comparison of US and unenhanced multi-detector row CT in patients suspected of having acute appendicitis.

PURPOSE: To prospectively compare the diagnostic performance of ultrasonography (US) and unenhanced multi-detector row computed tomography (CT) in patients suspected of having acute appendicitis by using surgery or clinical follow-up as the reference standard.

MATERIALS AND METHODS: The institutional review board approved the research protocol. Written informed consent was obtained from all patients or, for those who were adolescents, from their parents. Ninety-four patients (59 female and 35 male patients) aged 16-81 years (mean, 38 years) who were suspected of having acute appendicitis underwent both US and unenhanced multi-detector row CT of the entire abdomen. The examinations were performed within 1-2 hours of each other. US and CT images were obtained and prospectively interpreted by a different radiologist from a group of abdominal radiologists or a group of residents and general radiologists. Radiologists proposed an overall diagnosis and an alternative diagnosis. Data from US and CT were compared, and the definite diagnosis was established with surgical findings (n = 40) or results of clinical follow-up (n = 54) as the reference standard. Comparisons were made for each group of radiologists and the patient's age, body mass index (BMI), and sex. Proportion comparisons were made by using the Pearson chi2 test or the Fisher exact test. Continuous variables were compared between groups with the Mann-Whitney U test.

RESULTS: Thirty patients had definite appendicitis. The sensitivity, specificity, positive and negative predictive values, and accuracy were not significantly different between US and CT or between groups of radiologists (P values ranged from .389 to >.99), regardless of the patient's BMI (P values ranged from .073 to >.99). Misclassifications were compared with the definite alternative diagnosis and were not significantly different between US and CT or between groups of radiologists (P = .061-.592), regardless of patient age (P = .875) or sex (P = .151 and >.99 for male and female patients, respectively). The frequency of inconclusive examinations, however, was significantly higher with US than with CT, regardless of radiologist experience (P = .020 and <.001, respectively).

CONCLUSION: Although the diagnostic performances of US and multi-detector row CT are comparable, more inconclusive images were obtained with US.