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MP08-02 PATTERNS OF CT AND US UTILIZATION FOR NEPHROLITHIASIS IN THE EMERGENCY DEPARTMENT

INTRODUCTION AND OBJECTIVES: A previous randomized trial found that obtaining ultrasound (US) as the first diagnostic imaging study for adults with suspected ureteral stones reduces radiation without increasing return ED visits or missed diagnoses. These results are consistent with EAU guidelines that US should be the first imaging modality for nephrolithiasis. We sought to determine the potential reduction in radiation exposure for an US-first approach using population-based diagnostic imaging patterns in the ED. METHODS: We performed a cross-sectional study of adults who presented to 70 emergency departments in South Carolina between 1996 and 2017 using all payer hospital claims data. All ED encounters within a 6 month “episode” following the initial ED visit were identified, along with ultrasound and CT ordered at the visits. Patterns of US and CT during the first two consecutive ER visits were determined at the patient- and hospital-level. Imaging patterns in which only a CT was performed were classified as an “opportunity for reduction in CT″. RESULTS: From 1996 to 2017, 180,845 patients had 233,242 unique stone episodes involving at least 1 ED visit and 282,845 ED encounters. A CT was obtained in 72.8% of all ED encounters as compared to 3.5% with US. The median number of CTs obtained within a 6 month episode after the initial ED visit was 1 (IQR 0,1; range 1-13). The highest cumulative number of CTs was 80 for a single patient over the 18 year period. CT was obtained without US in 94.8% of all episodes during which an US and/or CT was obtained. Of those episodes that involved at least two consecutive ED visits, 79.1% represented an opportunity for reduction in CT use [Figure 1]. Twenty-eight percent of patients presented to different EDs for the initial and subsequent visits; CT utilization patterns between those who presented to the same ED and different EDs were similar (90% vs. 93.9%). There was an inverse relationship between hospital volume and CT utilization, which was clinically unimportant. CONCLUSIONS: The vast majority of ED encounters include CT alone. CT utilization was similar for repeat ED visits at the same and different hospitals. A US-first approach offers substantial potential for radiation reduction during ED visits for nephrolithiasis. Figure. No caption available. Source of Funding: None