Purpose: To validate a rapid 12-minute magnetic resonance imaging (MRI) protocol for diagnosing acute appendicitis in adults, addressing the need for accurate, ionising-radiation free MRI in patients presenting with acute abdominal pain. Methodology: Five-year retrospective cross-sectional study of 2,249 adult patients undergoing standardized 12-minute MRI for acute abdominal pain at Blacktown and Mt Druitt hospitals emergency departments (ED) from 2020 to 2024. Patient demographics, MRI reports and clinical documentation were extracted. The prevalence of appendicitis was 16% (354/2,249). MRI findings were compared against histopathology (n=328) as well as clinical follow-up (n=1921). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy with 95% confidence intervals were calculated. Results: The cohort was comprised of adult patients ranging from 18 to 93 years old (mean=27). MRI demonstrated 98.0% sensitivity (95% CI: 96.0-99.2), 99.8% specificity (99.5-99.9), 98.9% PPV (97.1-99.7), 99.6% NPV (99.2-99.9), and 99.5% overall accuracy (99.1-99.8). Of 342 appendicectomies performed, the negative appendicectomy rate was 4.7% (16/342). Alternate diagnoses were suggested in 61% (1365/2249) of patients. Conclusion: Rapid 12-minute MRI protocol achieves diagnostic accuracy comparable to CT while eliminating radiation exposure. MRI safely excludes appendicitis and identifies alternative pathology. This supports rapid MRI as a viable first-line imaging for suspected appendicitis in the emergency department.