Introduction Non-contrast helical CT (NHCT) became the procedure of choice for investigating Emergency Department (ED) patients presenting with suspected renal colic at Beaumont Hospital, Dublin, in 2008. The impact of NHCT on waiting times and patient management was compared with intravenous pyelography (IVP).

Methods A retrospective, comparative cohort analysis of 95 patients who had IVP and 109 patients who had NHCT was performed. Length of ED stay from time of scan ordering to referral or discharge was analysed relative to time of day and scan result.

Results Patients having NHCT who attended between 00:00–08:00 h, had a twofold longer length of stay than those who had IVP between the same hours (median 7.07 h vs 3.03 h, p=0.0294). The length of ED stay for patients attending between 08:00 and 24:00 h was similar in both groups. The presence of urolithiasis did not impact on length of stay. A significant alternate/incidental diagnosis was reported in 28 patients having NHCT, of which 12 were cancerous growths.

Conclusion NHCT allows for the detection of incidental/alternate diagnoses that may not be otherwise detected in patients with renal colic. Compared to IVP, NHCT has not impacted positively on the speed of patient processing in the ED under study. For patients presenting after midnight, it is associated with over a twofold longer length of stay from the time of scan ordering to referral or discharge. This leads to prolonged patient stays in the ED, and as such contributes to overcrowding.