O2171: Utility of Abdominal MRI in Pediatric Patients with Suspected Appendicitis Who Undergo Non-Diagnostic Ultrasound in a Low Resource Setting

Background: Pediatric patients with suspected appendicitis often undergo abdominal
ultrasound as an initial diagnostic modality. In pediatric surgery centers without dedicated high-quality ultra-sonographers, the appendix is frequently not visualized during abdominal ultrasound. This situation creates a clinical challenge for pediatric surgery and emergency department providers in deciding who should undergo additional diagnostic imaging like abdominal MRI. We evaluated 5 years of pediatric patients who underwent abdominal MRI after non-diagnostic ultrasounds to identify predictive factors of MRI positivity for appendicitis.

Methods: 411 pediatric patients were identified who underwent abdominal MRIs after non-
diagnostic abdominal ultrasounds. Chart review of each patient was performed with patient age, year evaluated, initial temperature, duration of symptoms, WBC, and CRP recorded for each patient. Additionally, ultrasound and MRI findings with specific radiologic descriptions were recorded. Data analysis was performed calculating odds ratios, sensitivity, and specificity for each variable’s contribution to predicting a positive MR.

Results: 9 out of 411 patients (or 2.1%) had positive MRIs indicating appendicitis. All patients
with MRI-confirmed appendicitis had elevated WBC, elevated CRP, elevated temperature, and at least 1 day of symptoms. Relatedly, there was a 97.9% negativity rate for MRI in patients with a high clinical concern for appendicitis. CRP <.3, normal WBC, and < 1 day of symptoms were all 100% sensitive for the absence of appendicitis on MRI.

Conclusion: Abdominal MRI after non-diagnostic abdominal ultrasound for appendicitis had a
high true negativity rate, which was predicted with high sensitivity by laboratory markers. Given the high healthcare utilization cost of obtaining an abdominal MRI, particularly in a lower resource hospital setting, a higher threshold for obtaining an abdominal MRI should be adopted for pediatric patients.