Background: Acute non-traumatic abdominal pain is typically evaluated by abdomino-pelvic computed tomography (CT) with oral and venous contrast. The accuracy of unenhanced CT for diagnosis in this setting has not been widely studied.

Objectives: To assess the accuracy of unenhanced CT in establishing the etiology of acute non-traumatic abdominal pain.

Methods: We retrospectively reviewed the medical and imaging records of patients aged ≥ 18 years who presented to the emergency department (ED) during a 6-month period with acute non-traumatic abdominal pain of unknown etiology, and who were evaluated with non-contrast CT within 24 hours of ED admission. Clinical details were recorded. A presumptive clinical diagnosis and CT diagnosis were compared to the discharge diagnosis which was considered the reference standard. The requirement for informed consent was waived.

Results: Altogether, 315 patients met the inclusion criteria – 138 males (44%) and 177 females (56%); their mean age was 45 years (range 18–90). Clinical diagnosis correlated with the CT findings in 162 of the cases (51%). CT was accurate in 296/315 cases (94%). The leading diagnosis in cases of a mismatch between CT diagnosis and discharge diagnosis was infection mostly in the urinary tract (12/18). Sensitivity, specificity, positive predictive value and negative predictive value were 91%, 99%, 91% and 85% respectively. The discharge diagnosis was unchanged in the patients who returned to the ED within 1 week of the first admission.

Conclusions: In this study, unenhanced CT proved to be a feasible, convenient and legitimate examination for the evaluation of patients with acute non-traumatic abdominal pain presenting to the ED.