Magnetic Resonance Imaging Provides Useful Diagnostic Information Following Equivocal Ultrasound in Children With Suspected Appendicitis

Purpose: In Canada, ultrasonography is the primary imaging modality for children with suspected appendicitis, yet equivocal studies are common. Magnetic resonance imaging provides promise as an adjunct imaging strategy. The primary objective of this study was to determine the proportion of children with suspected appendicitis and equivocal ultrasound where magnetic resonance imaging determined a diagnosis. Methods: A prospective consecutive cohort of children aged 5-17 years presenting to a tertiary pediatric Emergency Department with suspected appendicitis were enrolled. Participants underwent diagnostic and management strategies according to our local suspected appendicitis pathway, followed by magnetic resonance (Siemens Avanto 1.5 Tesla) imaging. Sub-specialty pediatric radiologists reported all images. Results: Magnetic resonance imaging was performed in 101 children with suspected appendicitis. The mean age was 11.9 (SD 3.4) years and median Pediatric Appendicitis Score was 6 [IQR 4,8]. Ultrasonography was completed in 98/101 (97.0%). Of 53/98 (54.1%) with equivocal ultrasound, magnetic resonance imaging provided further diagnostic information in 41 (77.4%; 10 positive, 31 negative; 12 remained equivocal). Secondary findings of appendicitis on magnetic resonance imaging in children with equivocal ultrasound included abdominal free fluid (24, 45.3%), peri-appendiceal fluid (12, 22.6%), intraluminal appendiceal fluid (9, 17.0%), fat stranding (8, 15.1%), appendicolith (2, 3.8%), and peri-appendiceal abscess (1, 1.9%). The observed agreement between magnetic resonance imaging results and final diagnosis was 94.9% (kappa = 0.89).