Assessment of clinically significant urolithiasis positivity rate using CT KUB for suspected renal colic

Unenhanced low-dose computed tomography of the kidneys, ureter and bladder (CT KUB) is the gold standard diagnostic imaging modality in the assessment of suspected renal colic. As the radiation dose is not negligible, it is important to monitor the diagnostic yield of CT KUBs. The aim of this study is to evaluate the diagnostic yield of CT KUB studies performed for suspected renal colic in patients presenting to the emergency department.

A retrospective review was performed of 500 patients who underwent CT KUB for suspected renal colic over a seven month period from June 2019 to January 2020. Clinical information and imaging was reviewed for each patient. Statistical analysis was performed using GraphPad Prism 8 (GraphPad Software, San Diego, CA, USA).

Forty-nine percent of patients in the series were female (248/500) and the mean age was 45. The positivity rate for obstructing ureteral calculus was 34% (169/500). Concerningly, there was a significantly lower positivity rate in females compared to males (19% versus 48%; p < 0.0001) which raises the issue of unnecessary radiation exposure to this cohort. In the 200 female patients who were negative for obstructing urolithiasis, the mean age was 43. Females also had a significantly higher rate of negative CT KUB (62% versus 37%; p < 0.0001) where no underlying alternative pathology was diagnosed.

Women are less likely than men to have obstructing urolithiasis on CT KUB for suspected renal colic. This difference is not accounted for by a higher rate of alternative diagnoses among female patients. The findings of this study should prompt clinicians to exercise caution when considering this imaging modality in this patient cohort.