Less than 8 percent of patients with suspected urinary stones underwent CT using appropriate low-dose techniques, according to a research letter published online in JAMA Internal Medicine.

The prospective, multicenter assessment, conducted by Rebecca Smith-Bindman, MD, of the University of California, San Francisco, and colleagues, also found wide variation in dose between patients and in median doses across hospitals.

“[CT] for the evaluation of suspected urolithiasis should use low-dose techniques (<4 mSv) given that diagnostic accuracy is equal to or better than that of conventional CT and that this technique reduces the risk for radiation-related carcinogenesis,” wrote the authors.

To evaluate whether these accepted low-dose techniques were indeed being used on patients with suspected urolithiasis, Smith-Bindman and colleagues collected data from the Study of Tomography of Nephrolithiasis Evaluation (STONE) trial, which compared CT and ultrasound imaging in these patients at 15 different facilities. A total of 1,582 patients with suspected urolithiasis who underwent CT from Oct. 1, 2011, though Feb. 28, 2013, were included in the study.

Of the study cohort, 497 (31.4 percent) passed or underwent surgical removal of a stone. The authors found a median effective dose of 11 mSv, with a 200-fold variation in dose between patients. Median effective dose varied across the 15 hospitals from 4 to 19 mSv, with differences persisting after accounting for patient factors.

The authors found only 121 patients (7.6 percent) underwent imaging with low-dose techniques. They compared this with data from the American College of Radiology Dose Index Registry, which also showed few renal colic protocol scans are conducted with low-dose techniques.

“The consistency of our results with those of the Dose Index Registry provides substantial evidence that appropriate low-dose studies are not used widely for the evaluation of suspected urolithiasis,” wrote Smith-Bindman and colleagues.