Assessing the Appropriateness of Outpatient Abdominopelvic CT and MRI Examinations Using the American College of Radiology Appropriateness Criteria

Rationale and Objectives: To retrospectively assess the appropriateness of outpatient abdominal and pelvic computed tomography (CT) and magnetic resonance imaging (MRI) examinations using the American College of Radiology Appropriateness Criteria (AC). Materials and Methods: A total of 570 adult outpatient abdominopelvic CT (304) and MRI (266) studies performed in a 1-month period with available documentation of the clinical encounter generating the imaging order were included. On the basis of review of the imaging report and patient record, examinations were classified in terms of match to a specific AC variant, appropriateness score, and the presence of a significant result. Data were analyzed using Fisher's exact test. Results: Forty-five percent of examinations matched an AC variant: 52% of CT and 38% of MRI (. P<.001). Ninety-two percent of examinations matching the AC were appropriate: 96% of CT and 86% of MRI (. P=.009). Appropriate examinations were more likely to provide a significant result than not appropriate studies (48% vs. 24%, P=.041). Although a significant result was related to the primary study indication more frequently in appropriate than not appropriate examinations, this difference was not significant (93% vs. 80%, respectively, P=.204). The most common indications not matching an AC were colon cancer follow-up (. n=14) and melanoma follow-up (. n=14) among CT, and hepatocellular carcinoma screening (. n=31) and elevated prostate-specific antigen (PSA) without prior biopsy (. n=14) among MRI. Conclusions: Most examinations matching the AC were appropriate, and appropriate examinations were more likely to have a significant result. However, most examinations, including 62% of MRI, had no relevant clinical condition, highlighting a critical area for future AC expansion and modification.