Background Patients presenting to the ED with suspected renal colic are frequently imaged with CT urography (CTU), which rarely alters diagnosis or management. To reduce use of CTU in this population, we instigated a new imaging and management guideline in our ED.

Methods This was a quasi-experimental prospective study, whereby a new guideline was commenced at the intervention site (Monash Medical Centre) and the existing guideline continued at the control site (Dandenong Hospital). The new guideline promotes focused ultrasound for diagnosing renal colic and restricts CT to those with poor response to analgesia or ‘red flags’. A consecutive series of patients with suspected renal colic were prospectively enrolled and outcomes compared between the sites. The primary outcome was CTU utilisation and secondary outcomes were radiation exposure, stone rate on CTU, admission, ED length of stay and rates of urological intervention and returns to ED at 4-week follow-up.

Results Preintervention CTU rates were 76.7% at Monash and 72.1% at Dandenong. 324 patients were enrolled; 148 at Monash and 176 at Dandenong. Median age 47 years vs 49 years, males 76.4% vs 66.5% and medianSex, Timing, Origin, Nausea, Erythrocytes (STONE) score 10 vs 10 for Monash and Dandenong, respectively. CTU was performed in 54.1% vs 75.0% (p<0.001), median radiation exposure 2.8 vs 4.0 mSv (p<0.001) and urological intervention occurred in 16.4% vs 15.7% for Monash and Dandenong, respectively.

Conclusions We found that use of CTU for renal colic was significantly reduced by introduction of a guideline promoting ultrasound and encouraging selective CTU. Although intervention rates were similar between the two sites, further prospective study is needed to ensure other patient-centred outcomes do not differ.