EAU 2018: Assessing the Diagnostic Accuracy of Low and Ultra-Low Radiation Dose CT of the Urinary Tract for the Investigation of Urolithiasis

Copenhagen, Denmark (UroToday.com) Acute renal colic, or abdominal pain commonly caused by kidney stones, is of significant prevalence in young patients. While CTKUB is the current gold standard test to assess the cause of acute renal colic, the radiation dose associated with CTKUB is unfavorable for these young patients and even more so for those with recurrent or chronic renal colic. As such, low and ultra-low dose CT of the urinary tract has been suggested as an alternative in this patient subset.

Dr. Rodger (MD) of Queen Elizabeth University Hospital Department of Urology in Glasgow, United Kingdom presented a systematic review of literature to assess the diagnostic accuracy of low and ultra-low radiation dose CT for the detection of urinary tract stones in patients with renal colic.

The systematic review was performed by two reviewers (consultant urologist and consultant radiologist) and included studies from 1995 through 2017. Low dose CT scans were defined as scans < 3.5mSv and ultra-low dose scans were defined as < 1.9mSv. Sensitivity and specificity of the scans were calculated and summary ROC curves were assessed across the studies.

Following initial screening, 12 studies and 1439 patients were included in the systematic review. Of these, 475 (33%) had low-dose CTs [mean effective doses 2.1-4.5mSv) and 964 (67%) had ultra-low dose CTs [mean effective does 0.48-1.9 mSv]. Sensitivity and specificity of the scans were generated utilizing standard doses, yielding a sensitivity of 90-98% and 72-99% sensitivity in the low- and ultra-low dose CT scans, respectively. In contrast, specificity ranged from 88-100% and 86-100% in the low- and ultra-low dose CT scan groups, respectively. ROC curve analysis showed 0.95 sensitivity, 0.97 specificity, 20.92 positive likelihood ratio, and 0.06 negative likelihood ration in ultra-low dose CT scans.

Overall, this systematic review confirms that ultra-low dose (and subsequently, low-dose) CTKUB are effective alternatives for the identification of urinary tract stones. While there always exists a trade-off between sensitivity and specificity, it is observed that these the predictive values of these scans have been maintained, along with the advantages of reduced radiation dose exposures. As such, the adoption of low and ultra-dose CTKUB presents with significant advantages for younger patients with recurrent renal colic and associated stone disease.

Presented by: Rodger F., Ng A., Santoni N., Rhoditi G., Aboumarzouk O

Author Information: Queen Elizabeth University Hospital, Dept. of Urology, Glasgow, United Kingdom

Written by: Linda M. Huynh, B.S, Department of Urology, University of California-Irvine at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark