Study objectives: Computed tomography (CT) scanner use has become increasingly common in US emergency departments (EDs). We undertake a study to investigate the change in frequency of the use of ED CT scans in patients with abdominal pain. We also investigated the relationship between CT scan use and changes in patient acuity.

Methods: Data were obtained from the 1996 to 2000 National Hospital Ambulatory Medical Care Survey (NHAMCS), a national probability sample survey conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention. All visits that were coded as nonspecific abdominal pain (International Classification of Diseases, Ninth Revision code 789) were identified. Data were collected for the use of blood tests. Indicators of patient severity (triage category and hospital admission rates) were also collected, and demographic data were obtained. Continuous variables were summarized by mean and SDs. Proportions were compared with a χ² test; an a priori significance level of P value less than .05 was selected. Descriptive analyses were performed with statistical software (Microsoft Excel 2000 version 9.0; Microsoft Corporation, Redmond, WA). The data used for this study are openly accessible to the public and excluded all patient identifiers. The study was therefore exempt from institutional board review approval.

Results: We analyzed 115,011 visits that represented 496.4 million visits to US EDs during the 5-year study period. Data were weighted in accordance with NHAMCS guidelines for statistical analysis. Three thousand five hundred sixty-four patients with a final ED diagnosis of nonspecific abdominal pain were identified, representing 15,767,037 weighted patient visits nationally. There was a slight increase in the percentage of patients with nonspecific abdominal pain (2.7% in 1996, 3.3% in 2000, χ²=13.7, P=.001). The rate of CT scan use increased from 1.7% to 10.2% (χ²=40.4, P=.001). The hospital admission rate decreased from 15.6% (350,588 admissions) in 1996 to 14.9% (573,784 admissions) in 2000 (χ²=0.13, P=NS). There was a decrease in the triage acuity of patients with abdominal pain presenting to the ED. The presenting acuity of patients as categorized by a triage level one (to be seen within ≤15 minutes) decreased significantly from 22.4% to 10.8% (χ²=36.4, P=.001). There was a 10-fold increase in the rate of CT use in admitted patients (3.3% in 1996, increasing to 37.4% in 2000). The use of a CBC count increased from 56% to 65% (χ²=5.0, P=.05). Overall, the growth in CT scanning was higher than for the growth in the use of a CBC count or hospital admission rate, which suggests that despite a decreasing patient acuity, the rate of CT scan use is increasing. Projections based on 5 years of data suggest that if current growth continues, by 2010 more than 30% of all ED patients with a final diagnosis of nonspecific abdominal pain will undergo a CT scan while in the ED.

Conclusion: The use of CT scanning in patients with nonspecific abdominal pain is increasing rapidly. This increase cannot be explained by increasing patient acuity and has not changed the admission rate. These trends need to be factored into ED design. Further studies involving patients most likely to benefit from a CT may result in large cost savings and may ease ED congestion.