To evaluate the diagnostic performance and the benefit in terms of management of low-dose CT for the imaging assessment of renal colic (CN) emergencies. Two hundred and ninety-one patients admitted to emergency for CN were included in this study. Eighty-seven had a low-dose CT and 40 an ASP and an ultrasound (ASPE). Different parameters evaluating the diagnostic performance and efficiency of care were compared between the two groups. The quantitative and qualitative variables were compared by Student t test and χ(2) test, respectively. CT and ASPE confirmed the diagnosis of CN in 76% and 54% of patients, respectively (p=0.013). The average lengths of stay were 408 minutes versus 520 (p=0.013) in group scanner and ASPE, respectively. The scan was obtained more rapidly (139 min versus 224, p=0.002). There were more requests for expert advice (30% versus 20%, p=0.18) and gestures endo-urology (9.5% versus 5%, p=0.31) in the CT group compared to the group ASPE. Finally, the patients in the scanner have less painful recurrences (6% versus 12.5%, p=0.18) and fewer imaging examinations of second-line (0% versus 30%, p<0.001). The low dose CT has been more efficient than the couple ASPE for a CN diagnosis. It optimizes the management of emergency patients by reducing their length of stay, waiting time and the rate of second consultation.