Background: In recent years, the use of abdominal pelvic computed tomography (APCT) in the emergency department (ED) for patients with Crohn's disease (CD) has risen steadily. Thus, exposing these patients to recurrent radiation, despite studies showing that only 30% to 40% had significant findings in ED APCT. Goal: Our aim was to find clinical and laboratory variables that can predict substantial findings on ED APCT, which may require invasive intervention. Methods: We analyzed ED visits of patients with known CD that underwent an emergent APCT for gastrointestinal complaints, over a 10-year period. Patients with positive and negative findings in the APCT were compared in order to evaluate independent effects of different variables, including patients' characteristics, CD history, ED complaints, and laboratory tests. Results: In 44% of 183 ED visits, there were significant findings on ED APCT, however, only 22% of them underwent invasive intervention. Laboratory tests: C-reactive protein >50 mg/L, neutrophil count >75%, platelet count >350x10(9)/L, and ileocolon location at diagnosis were all positive predicting factors. Whereas, smoking or ED complaints of diarrhea/fever reduced the risk for significant findings. Conclusions: Using the 7 most significant predicting factors, we built an easy to use scoring system-Crohn Assessment Tool for CT upon Hospitalization (CATCH) for ED clinicians. This scoring system could have prevented unnecessary ED APCT from 42% of the patients in our study, without missing those who required invasive intervention.