Magnetic Resonance Imaging Versus Ultrasound as the Initial Imaging Modality for Pediatric and Young Adult Patients With Suspected Appendicitis.

Background: While ultrasound (US), given its lack of ionizing radiation, is currently the recommended initial imaging study of choice for the diagnosis of appendicitis in pediatric and young adult patients, it does have significant shortcomings. US is time-intensive and operator dependent and results in frequent inconclusive studies, thus necessitating further imaging and admission for observation or repeat clinical visits. A rapid focused magnetic resonance imaging (MRI) for appendicitis has been shown to have definitive sensitivity and specificity, similar to computed tomography but without radiation and offers a potential alternative to US.

Objective: In this single-center prospective cohort study, we sought to determine the difference in total length of stay and charges between rapid MRI and US as the initial imaging modality in pediatric and young adult patients presenting to the emergency department (ED) with suspected appendicitis. We hypothesized that rapid MRI would be more efficient and cost-effective than US as the initial imaging modality in the ED diagnosis of appendicitis.

Methods: A prospective randomized cohort study of consecutive patients was conducted in patients 2 to 30 years of age in an academic ED with access to both rapid MRI and US imaging modalities 24/7. Prior to the start of the study, the days of the week were randomized to either rapid MRI or US as the initial imaging modality. Physicians evaluated patients with suspected appendicitis per their usual manner. If the physician decided to obtain radiologic imaging, the predetermined imaging modality for the day of the week was used. All decisions regarding other diagnostic testing and/or further imaging were left to the physician's discretion. Time intervals (minutes) between triage, order placement, start of imaging, end of imaging, image result, and disposition (discharge vs. admission), as well as total charges (diagnostic testing, imaging, and repeat ED visits) were recorded.

Results: Over a 100-day period, 82 patients were imaged to evaluate for appendicitis; 45 of 82 (55%) of patients were in the US-first group, and 37 of 82 (45%) patients were in the rapid MRI-first group. There were no differences in patient demographics or clinical characteristics between the groups and no cases of missed appendicitis in either group. Eleven of 45 (24%) of US-first patients had inconclusive studies, resulting in follow-up rapid MRI and five return ED visits contrasted with no inconclusive studies or return visits (p < 0.05) in the rapid MRI group. The rapid MRI compared to US group was associated with longer ED length of stay (mean difference = 100 minutes; 95% confidence interval [CI] = 35-169 minutes) and increased ED charges (mean difference = $4,887; 95% CI = $1,821-$8,513).

Conclusions: In the diagnosis of appendicitis, US-first imaging is more time-efficient and less costly than rapid MRI despite inconclusive studies after US imaging. Unless the process of obtaining a rapid MRI becomes more efficient and less expensive, US should be the first-line imaging modality for appendicitis in patients 2 to 30 years of age.