Purpose or Case Report: Non-contrast MRI with focused rapid-acquisition sequences can be used in place of CT for effective diagnosis of pediatric acute appendicitis (PAS). However, higher costs and limited resources are major considerations when considering its use. The goal of this study was to evaluate accuracy, utilization, and cost of MR compared to US and CT in the diagnosis of PAS.
Methods & Materials: A clinical protocol was developed to study the feasibility of limited abdominal MRI for PAS during a 1-month pilot in the emergency department. MR could be ordered either after indeterminate US or prior to any other imaging. Qualifying patients were at least 5 years old, hemodynamically stable, able to remain still for 10 minutes without sedation, and had no MR contraindications. A 3T magnet was used, without expansion of technologist work hours. MR sequences included axial and coronal single shot fast spin echo, with and without and without fat saturation, with 4mm slice thickness through the abdomen and pelvis. Exams were interpreted by dedicated pediatric radiologists. Positive cases were correlated with surgical pathology. Negative cases were confirmed with patient follow-up by phone or EMR documentation. Comparison US/CT data was obtained from the 4 month period preceding MR pilot.
Results: A total of 50 MR cases were ordered. 15 were not scanned due to scanner availability or patient contraindication. Of 35 MR cases completed, 31% were positive, with 100% pathologic accuracy. In comparison, US cases were 11% positive (99% accuracy) and CT cases were 18% positive (100% accuracy). Appendix nonvisualization rate was 9% on MRI, 47% on US. 17% of US cases led to further imaging with CT. 89% of MR cases were performed without preceding US, with referrers citing its primary use in obese patients, females, or during surging ER wait times. CPT codes and charges: limited abdominal US (76705, $482.50), CT abdomen and pelvis with contrast (74177, $6753.50), and limited abdominal MR (76498, $3086.25).
Conclusions: MR for pediatric acute appendicitis is equally accurate but can cost less than half as much as CT with contrast. Additional benefits include decreased risks of ionizing radiation and contrast administration. Compared to patients who receive both US and CT, MR may reduce ER patient turnaround time and need for additional imaging (such as pelvic US in females). Given these benefits, MR may be considered as a lower-cost and faster first-line modality in patients who are at higher risk for needing both US and CT.