Renal colic imaging practice patterns in Ontario A population-based study.

Introduction: Computed tomography (CT) is associated with increased cost and exposure to radiation when compared to ultrasound (US) in patients with renal colic. Consequently, a 2014 Choosing Wisely recommendation states US should be used over CT in uncomplicated presentations in patients under age 50. The objective of this study was to describe imaging practice patterns in Ontario among patients presenting with renal colic and the relationship between initial imaging modality, subsequent imaging, and burden of care indicators.

Methods: This is a population-based study of patients who presented with renal colic in Ontario from 2003-2019 using administrative data. Patients were assessed according to their first imaging modality during their index visit. Descriptive statistics and Chi-squared test were used to examine differences between these groups. The primary outcome was the need for subsequent imaging. Secondary outcomes were length of renal colic episode, days to surgery, and number of emergency department (ED ) and primary care visits during the renal colic episode. Univariate and multivariable logistic regression models were used.

Results: A total of 429 060 patients were included in the final analysis. Of those, 50.5% (216 747) had CT as their initial imaging modality, 20% (84 672) had US, and 3% (13 643) had both on the same day. Subsequent imaging was obtained in 40.7% of those who had CT as the initial imaging, compared to 43% in those who had US and 43% who had both. Of those who initially had an US, 38% went on to have at least one CT during their renal colic episode, including those who had CT on the same day as initial US, while 62% were able to avoid CT altogether. In contrast, 17% had a repeat CT after an initial CT at the time of presentation. The overall use of US increased from 15% to 31% during the study period. The length of the renal colic episode was slightly longer in those who had a CT first compared to US in multivariable models (adjusted risk ratio [ARR ] 1.005, 95% confidence interval [CI] 1.000-1.009); however, the time to surgery was less in those who had a CT first (ARR 0.831, 95% CI 0.807-0.856). Fewer ED and family physician visits were seen in those who had an initial CT.

Conclusions: In patients with renal colic in Ontario, approximately half have CT as the initial imaging modality despite US being recommended in uncomplicated presentations. While US use remains low, its use doubled during this study period, demonstrating an encouraging trend. Those who have US first can often avoid subsequent CT.