Abstract Purpose To investigate temporal changes in the utilization and patient impact of abdominal CT during duty shifts in the past 15 years. Methods This study included a random sample of 1761 abdominal CT scans that were made during evening and night duty shifts in a tertiary care center between 2005 and 2019. Results The number of CT scans significantly increased (almost threefold) between 2005 and 2019 (Mann–Kendall tau of 0.829, P < 0.001). The proportion of negative CT scans (i.e., the absence of findings related to the reason that the CT scan was made and no disease deterioration or other new and clinically relevant findings compared to a previous imaging examination when available) was 40.0% (700/1749) in the entire 15-year study frame and did not significantly change over time (Mann–Kendall tau of − 0.219, P = 0.276). The overall frequency of same-day hospital discharge after negative CT was 20.6% (150/729) in the past 15 years and showed a significant increase over time (Mann–Kendall tau of 0.505, P = 0.010). The overall proportion of CT scans with incidental findings was 3.4% (60/1761) and remained statistically stable over the past 15 years (Mann–Kendall tau of − 0.057, P = 0.804). Conclusion Over the past 15 years, the number of CT scans and the frequency of same-day hospital discharge after negative CT have increased, while the proportions of negative CT scans and incidental findings have remained stable in our tertiary care center. The data from this study can be used for interinstitutional benchmarking to define, monitor, and improve the appropriateness of imaging utilization.