The purpose of this study was to compare the diagnostic accuracy and inter-reader agreement of unenhanced computed tomography (CT) to those of contrast-enhanced CT for triage of patients older than 75years admitted to emergency department (ED) with acute abdominal pain (AAP).

Two hundred and eight consecutive patients presenting with AAP to the ED who underwent CT with unenhanced and contrast-enhanced images were retrospectively included. There were 90 men and 118 women with a mean age of 85.4±4.9 (SD) (range: 75–101.4years). Three readers reviewed unenhanced CT images first, and then unenhanced and contrast-enhanced CT images as a single set. Diagnostic accuracy was compared to the standard of reference defined as the final diagnosis obtained after complete clinico-biological and radiological evaluation. Correctness of the working diagnosis proposed by the ED physician was evaluated. Intra- and inter-reader agreements were calculated using the kappa test and interclass correlation. Subgroup analyses were performed for patients requiring only conservative management and for those requiring intervention.

Diagnostic accuracy ranged from 64% (95% CI: 62–66%) to 68% (95% CI: 66–70%) for unenhanced CT, and from 68% (95% CI: 66–70%) to 71% (95% CI: 69–73%) for both unenhanced and contrast-enhanced CT. Contrast-enhanced CT did not significantly improve the diagnostic accuracy (P=0.973–0.979). CT corrected the working diagnosis proposed by the ED physician in 59.1% (range: 58.1–60.0%) and 61.2% (range: 57.6–65.5%) of patients before and after contrast injection (P>0.05). Intra-observer agreement was moderate to substantial (k=0.513–0.711). Inter-reader agreement was substantial for unenhanced (kappa=0.745–0.789) and combined unenhanced and contrast-enhanced CT (kappa=0.745–0.799). Results were similar in subgroup analyses.

Unenhanced CT alone is accurate and associated with high degrees of inter-reader agreement for clinical triage of patients older than 75years with AAP in the emergency setting.