Introduction: Computed tomography (CT) is associated with increased cost and exposure to radiation when compared to ultrasound (US). Choosing Wisely recommends that US be used over CT in uncomplicated presentations of renal colic for patients under age 50. This objective of this study was to describe imaging practice patterns in Ontario among patients presenting with renal colic.

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 imaging modality obtained during their index visit. Descriptive statistics and the Chi-squared test were used to examine differences between the groups. The primary outcome was the need for subsequent imaging. Secondary outcomes included length of renal colic episode, days to surgery, and the number of emergency department and primary care visits during the renal colic episode.

Results: A total of 429 060 patients were included in the analysis. Of those, 50.5% had a CT scan as their initial imaging modality, 19.7% had an US, and 3.2% had both a CT and an US on the same day. Rates of any subsequent imaging were similar accross these groups. Of those who initially had an US, 38.0% 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 62.0% were able to avoid a CT scan altogether. In contrast, 16.8% had a repeat CT after an initial CT at the time of presentation. 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 have a CT as initial imaging despite US being recommended in uncomplicated renal colic patients. Those who have an US done first are often able to avoid subsequent CT scans. Efforts should be made to encourage the use of US in those presenting with renal colic rather than CT when clinically indicated.