Assessing the necessity of intravenous contrast for computed tomography in the acute undifferentiated abdomen

Introduction: Undifferentiated abdominal pain in the emergency setting is frequently investigated with an intravenous contrast enhanced CT as a first line diagnostic test. However, global contrast shortages restricted the use of contrast for a period in 2022, altering standard practice with many scans performed without intravenous contrast. Whilst IV contrast can be useful to assist with interpretation, its necessity in the setting of acute undifferentiated abdominal pain is not well described, and its use comes with its own risks. This study aimed to assess the shortcomings of omitting IV contrast in an emergency setting, by comparing the rate of CT scans with "indeterminate" findings with and without the use of IV contrast.

Methods: Data from presentations to a single centre emergency department for undifferentiated abdominal pain prior to and during contrast shortages in June 2022 were retrospectively compared. The primary outcome was the rate of diagnostic uncertainty, where the presence or absence of intra-abdominal pathology could not be ascertained.

Results: 12/85 (14.1%) of the unenhanced abdominal CT scans provided an uncertain result, compared with 14/101 (13.9%) of control cases performed with intravenous contrast (P = 0.96). There were also similar rates of positive and negative findings between the groups.

Conclusion: Omitting intravenous contrast for abdominal CT in the setting of undifferentiated abdominal pain demonstrated no significant difference in the rate of diagnostic uncertainty. There are significant potential patient, fiscal and societal benefits as well as potential improvements to emergency department efficiency with the reduction of unnecessary intravenous contrast administration.