A National Study on the Association of Abdominal Ultrasound with CT Utilization and Disposition in the Emergency Department

Background Ultrasound and CT imaging have distinct and overlapping roles in the assessment of undifferentiated abdominal pain in the emergency department (ED). CT imaging is the gold standard for many pathologies, ranging from bowel obstruction to aortic pathology whereas ultrasound benefits from less radiation exposure and the ability to employ at bedside. In this pilot study, we utilize nationally representative data to identify associations between ultrasound use in ED patients with a primary complaint of abdominal pain with abdominal CT imaging use and disposition. Methods We analyzed retrospective, cross-sectional data on ED patient visits obtained from the National Hospital Ambulatory Medical Care Survey from 2016-2020. This dataset utilizes a weighed multistage, probability sample of ED patient visits involving a four-stage sampling design, including data at county-level geographic regions, hospitals within these regions, emergency service areas in these hospitals, and patient visit records. The study population includes adult patient ED visits with an age of 18 and up presenting with a primary complaint of atraumatic abdominal pain. Descriptive statistics was utilized to describe the sample population. Survey-weighted multivariate logistic regression analysis with calculated odds ratios evaluated for differences between the binary dependent variable of abdominal pain visits with versus without ultrasound use with independent variables of disposition and abdominal CT imaging use while controlling for visit acuity and adjusting for demographic information. Results A total of 7563 patient visits met inclusion criteria, representing approximately 60 million patient visits from 2016-2020. In this study population, 18.5% of visits involved ultrasound, whereas 39.8% of visits involved CT imaging use. 14.6% of visits resulted in hospital admission. On weight-adjusted regression analysis, visits involving ultrasound were less likely to require CT imaging and more likely to be admitted, with ORs of 0.49 (95% CI: 0.37, 0.64) and 1.97 (95% CI: 1.44, 2.68), respectively. Visits involving ultrasound were more likely to be associated with an emergency medicine residency program and an emergent acuity level, with ORs of 1.40 (95% CI: 1.01, 1.94) and 1.53 (95% CI: 1.01, 2.31), respectively. Conclusion In this national pilot study, abdominal pain visits involving ultrasound were associated with a lower likelihood of CT imaging use and a highly likelihood admission and an emergent acuity level.