Renal colic imaging practice patterns in Ontario: a population-based study

Introduction — Computed tomography (CT) scans are associated with increased cost and exposure to radiation when compared to ultrasound (US) in patients presenting with renal colic. Consequently, a Choosing Wisely recommendation from 2014 states that US should be used over CT in uncomplicated presentations of renal colic in patients under the age of 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 between 2003 and 2019 using administrative data. Patients were assessed according to the first imaging modality they had during their index visit. Descriptive statistics and the Chi-squared test were used to examine differences between these groups. The primary outcome was the need for subsequent imaging. Secondary outcomes included length of renal colic episode, days to surgery, number of emergency department visits, and number of primary care visits during the renal colic episode. To identify the factors associated with outcomes, both 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 a CT scan as their initial imaging modality, 20% (84 672) had an US, and 3% (13 643) had both a CT and an US on the same day. Subsequent imaging was obtained in 40.7% of those who had a CT scan as the initial imaging, compared to 43% in those who had an US and 43% who had both an US at CT on the same day. Of those who initially had an US, 38% went on to have at least one CT scan during their renal colic episode, including those who had a CT on the same day as the initial US, while 62% were able to avoid a CT scan 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 (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 emergency department and family physician visits were seen in those who had an initial CT.

Conclusions — In patients presenting with renal colic in Ontario, approximately half are having a CT done as the initial imaging modality despite US being the recommended imaging modality in uncomplicated renal colic presentations. While US use remains low, its use doubled during this study period, demonstrating an encouraging trend. Those who have an US done first are often able to avoid subsequent CT scans. Efforts should be made to further promote the use of US in those presenting with renal colic rather than CT when clinically indicated.