Date of Award

January 2018

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Christopher L. Moore


Over 2 million patients present to emergency departments (ED) in the U.S. every year with acute flank pain, and 70% of these patients undergo a CT scan. The American College of Radiology (ACR) recommends evaluating acute flank pain with reduced-radiation CT, however in 2011-2012 only 2% of these CT examinations were performed with a reduced-radiation dose technique.

This project aimed to (1) determine optimal diagnostic strategy for patients presenting to the emergency department with suspected nephrolithiasis, (2) determine current utilization of reduced-radiation CT for kidney stone and establish an updated national average of radiation exposure from kindney stone CT, and (3) to perform and measure the effect of a randomized time-delayed intervention designed to increase utilization of reduced-radiation CT at facilities nationwide.

These three aims were achieved by (1) performing a decision tree analysis that employed modified-Markov modeling to determine optimal diagnostic strategy for suspected kidney stone, (2) performing a retrospective cross-sectional analysis using data provided by the Dose Index Registry (DIR) on radiation dose of single-phased, non-contrast kidney stone CT in the U.S., and (3) disseminating information and providing personalized consultation to U.S. facilities to enhance appropriate utilization of reduced-radiation CT for kidney stone evaluation through a delayed-intervention trial. This trial randomized 380 facilities to control or an intervention that tested the effect of free access to online educational modules and personalized consultation on kidney stone CT protocols on the facility’s ability to decrease radiation exposure from kidney stone CT.

The decision tree analysis concluded that reduced-radiation CT was the optimal diagnostic strategy and yielded an additional 2.4 quality-adjusted life years (QALYs) per 1000 patients compared to standard-radiation CT. Radiology ultrasound and point-of-care ultrasound yielded 1.7 and 1.5 QALYs respectively per 1,000-person-years more than standard CT, while no imaging was associated with a decrease of 17.5 QALYs per 1,000-person-years. Continuing with standard abdomen/pelvic CT in the place of reduced-radiation CT projected an additional 500 radiation-induced malignancies over the lifetime of patients scanned in one year.

Despite recommendations by the ACR, utilization of reduced-radiation CT for kidney stone in June 2015-July 2016 was 7.6% (8,040 of 105,334 CTs). At the time of preparing this thesis, the DOSE initiative had enrolled 65 facilities of the 154 facilities randomized to intervention, and of those 65, 17 had made changes to their kidney stone CT protocols.

This analysis concludes that reduced-radiation CT is the optimal diagnostic strategy to employ when evaluating acute flank pain in the emergency department, however this approach is currently underutilized. Implementation of a reduced dose CT technique is dependent on the facility having protocols for dose reduction in place, and even with free consultation, making changes to CT protocols is a slow process. Collabortaion between emergency physicians and radiologists is needed to develop and appropriately implement these protocols.


This thesis is restricted to Yale network users only. It will be made publicly available on 06/25/2100