Comparison of abdominopelvic non-contrast CT and contrast-enhanced CT in the diagnosis of non-traumatic acute abdomen

Background: The guidelines recommend that Computed Tomography (CT) may be indicated in all non-traumatic acute abdomen patients in the emergency department, but there is no specific recommendation for non-contrast or contrast-enhanced CT. In this study, we compared the value of non-contrast CT and contrast-enhanced CT in the diagnosis of non-traumatic acute abdomen. Methods Patients with non-traumatic acute abdomen who presented to the Department of Emergency Surgery of Peking University First Hospital and performed abdominopelvic contrast-enhanced CT from October 2019 to September 2021 were enrolled. The diagnostic consistency between non-contrast CT sequence and contrast-enhanced CT sequence, time cost for diagnosis based on CT image and diagnostic confidence were compared. Results 450 patients were included in this study. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of non-contrast CT and contrast-enhanced CT were 91.7%, 92.9%, 99.8%, 26.5% and 91.8% versus 97.9%, 92.9%, 99.8%, 59.1% and 97.8%. The diagnostic consistency between non-contrast CT and contrast-enhanced CT was 94%.The time cost of diagnosis based on non-contrast CT was shorter than that of contrast-enhanced CT(2.35 ± 1.097min vs 2.82 ± 1.767min, t =-12.591, P  = 0.000),and the confidence score was lower than that of contrast-enhanced CT(2.52 ± 0.634 vs 2.83 ± 0.402, t =-12.175, P  = 0.000). Conclusion It may be more appropriate to use non-contrast CT as the first imaging examination for the diagnosis of non-traumatic acute abdomen, while contrast-enhanced CT as a necessary supplement.