Abdominal Plain Film in Patients Admitted with Clinical Suspicion of Renal Colic: Should It Be Replaced by Low-dose Computed Tomography?

Objectives: To evaluate a low-dose abdominal computed tomography (LDCT) protocol, delivering a radiation dose close to that delivered by an abdominal plain film (APF), in patients with a clinical suspicion of renal colic.

Methods: A total of 139 patients for whom an APF was requested for suspicion of renal colic were randomized into two groups. The patients in group 1 (n = 68) underwent an admission LDCT scan delivering a 2.1-mSv radiation dose to women and 1.6 mSv to men, instead of the APF. Patients in group 2 (n = 71) underwent an APF. Clinical and radiologic follow-up data were obtained for each patient. The number of additional abdominal ultrasound and CT scans performed to reach a confident final diagnosis and determine the proper treatment was compared between the two groups. A mean effective radiation dose was obtained in each group.

Results: Of the 68 patients in group 1 (LDCT), 10 (15%) underwent ultrasonography, 9 (13%) conventional abdominal CT, and 2 (3%) both. In group 2 (APF), the corresponding percentages were 27% (19 of 71), 28% (20 of 71), and 23% (16 of 71). Of the 68 patients in group 1, 47 (69%) did not require any additional examinations compared with 16 (23%) of the 71 patients in group 2 (P < 0.0001). The mean effective dose was 3.5 and 6.9 mSv in groups 1 and 2, respectively (P < 0.0001).

Conclusions: In patients with suspicion of renal colic, replacing the admission APF with our LDCT protocol will significantly reduce the need for additional CT or ultrasonography. Also, our LDCT protocol decreases by almost 50% the mean radiation dose per patient.