Prevalence of alternative diagnoses in patients with suspected uncomplicated renal colic undergoing computed tomography: a prospective study.

OBJECTIVES Unenhanced computed tomography (CT) has become a standard imaging technique for uncomplicated renal colic in many countries. The appropriate timing of CT imaging has not been established, and guidelines recommend that this imaging be performed between 1 and 7 days of presentation. The primary objective of this study was to determine the prevalence of alternative diagnosis identified with low-dose unenhanced CT in the emergency department (ED) in patients with suspected uncomplicated renal colic. METHODS This prospective single-centre study was carried out in a large university hospital ED. Over a 6-month period, all patients with clinically diagnosed renal colic and a plan to be discharged underwent low-dose unenhanced CT in the ED. Pregnant women, women of childbearing age not willing to have a pregnancy test, and patients who had already undergone diagnostic imaging were excluded. The primary outcome was the number and nature of the alternative diagnosis. Univariate analyses were performed to assess factors associated with the primary outcome. RESULTS A total of 178 patients were screened, and 155 underwent CT in the ED. The mean age was 42.2 years; 69% were male. The diagnosis of uncomplicated renal colic was confirmed in 118 participants (76%); 27 (17%) had an inconclusive CT scan. Overall, 10 patients (6%; 95% confidence interval [CI] 3-10) had an alternative diagnosis, 5 of whom were subsequently hospitalized. CONCLUSION Low-dose unenhanced CT in the ED detects alternative diagnoses in 6% (95% CI 3-10) of patients with suspected uncomplicated renal colic, half of whom are subsequently hospitalized. Our prospective findings, which were similar to those reported in retrospective studies, are a potential argument for a systematic approach to ED imaging in suspected renal colic. Future research involving intervention and control groups would be helpful.