Category: Imaging & Image Guided Therapy: Radiation Safety

MP4-16 - Patterns of CT and US Utilization for Nephrolithiasis in the Emergency Department

Fri, Sep 21
10:00 AM - 12:00 PM

Introduction & Objective :

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 76 emergency departments in South Carolina between 1996 and 2014 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 – 2014, 153,104 patients had 191,616 unique stone episodes involving at least 1 ED visit and 222,585 ED encounters.  A CT was obtained in 68.7% 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 [Figure 2].


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.

Gregory E. Tasian

Assistant Professor of Urology and Epidemiology
The Children's Hospital of Philadelphia
Philadelphia, Pennsylvania

Gregory Tasian, MD, MSc, MSCE is an Assistant Professor of Urology and Epidemiology and a Senior Scholar in the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania Perelman School of Medicine. His clinical practice and research program are based at the Children’s Hospital of Philadelphia (CHOP), where he has faculty appointments in the Division of Urology and the Center for Pediatric Clinical Effectiveness. He is a practicing pediatric urologist with a clinical focus on kidney stone disease, and is Surgical Director of the Pediatric Kidney Stone Center at CHOP. His research is devoted to decreasing the lifetime burden of kidney stone disease, with a particular emphasis on clinical trials of interventions to improve health behaviors to decrease kidney stone recurrence, comparative effectiveness of surgical interventions for kidney stones, the environmental epidemiology of nephrolithiasis, and understanding the role of the gut microbiome in kidney stone disease. He also has an active research program in imaging classification and predictors of chronic kidney disease (CKD) progression for children with congenital abnormalities of the kidney and urinary tract.

Diana K. Bowen

Philadelphia, Pennsylvania

Lihai Song

Philadelphia, Pennsylvania