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

Authors:
Anna Willingham, Jason McKee, Lena Perger, Noah Lucero, Rachel Sidebottom

Body of Abstract:
Authors: A.Willingham1, N. Lucero1, R. Sidebottom1, L.Perger2, J. McKee2
1University of New Mexico, School of Medicine, Albuquerque, NM, USA
2University of New Mexico, Department Of Surgery, Albuquerque, NM, USA

Background: Pediatric patients with suspected appendicitis often undergo abdominal ultrasound as the initial diagnostic modality. However, in pediatric surgery centers without access to high-quality, dedicated ultra-sonographers, the appendix is frequently not visualized, leading to non-diagnostic results. This poses a clinical challenge for pediatric surgery and emergency department providers in determining who should undergo additional diagnostic imaging, such as abdominal MRI. To address this issue, we evaluated 5 years of pediatric patients at the University of New Mexico Hospital who underwent abdominal MRI following non-diagnostic ultrasounds to identify predictive factors of MRI-confirmed appendicitis.

Methods: A total of 411 pediatric patients who underwent abdominal MRI following non-diagnostic abdominal ultrasounds were identified. A comprehensive chart review of each patient was performed to collect data on patient age, year evaluated, maximum temperature reported, symptom duration, white blood cell count (WBC), and C-reactive protein (CRP) levels. Radiologic findings, including specification descriptions from ultrasound, CT, and MRI studies, were also recorded. Data analysis involved calculating relative risk ratios, sensitivity, and specificity for each variable to determine its contribution to predicting a positive MRI result.

Results: Of the 411 patients included in the study, 9 (2.1%) had positive MRI findings consistent with appendicitis. All patients with appendicitis met at least one diagnostic criterion, such as elevated WBC or CRP. Among these patients, 8 out of 9 had elevated WBC counts (>11.0) and elevated CRP levels (>0.5), while 4 out of 9 had a temperature >38°C. The sensitivity and specificity for WBC were 0.89 and 0.63, respectively, while CRP had a sensitivity of 0.89 and specificity of 0.51. In contrast, temperature >38°C demonstrated a lower sensitivity of 0.44 but a higher specificity of 0.81. These findings highlight the diagnostic value of combining clinical and laboratory parameters to identify appendicitis.

Conclusion: Abdominal MRI following a non-diagnostic abdominal ultrasound for appendicitis demonstrated a high true negative rate, with elevated WBC and CRP levels serving as highly sensitive predictors. 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.