The following article is part of conference coverage from the 2018 American Urological Association meeting in San Francisco. Renal and Urology News’ staff will be reporting live on medical studies conducted by urologists and other specialists who are tops in their field in kidney stones, prostate cancer, kidney cancer, bladder cancer, enlarged prostate, and more. Check back for the latest news from AUA 2018. 

SAN FRANCISCO—Ultrasonography is being used increasingly in emergency departments as the first imaging modality for patients with acute renal colic, but initial use of computed tomography (CT) in this setting has remained stable despite concerns about unnecessarily exposing patients to excessive ionizing radiation, researchers reported at the American Urological Association 2018 annual meeting.

In a study of 830,785 patients who sought care in an emergency department (ED) for acute renal colic, investigators led by Jonathan Harper, MD, of the University of Washington in Seattle, found that ultrasound (US) imaging alone increased from 2.7% in 2007 to 6.9% in 2015. During that same interval, initial use of CT scans declined only slightly—from 86.3% to 85.8%—despite previous studies establishing the safety of using US as the first imaging test for acute renal colic.

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CT imaging within 6 months prior to the index ED presentation increases the likelihood of US for evaluating acute renal stones, the investigators reported. Receiving US imaging in the ED decreases the average number of CT evaluations over 90 days by up to 0.4 CT evaluations.

The proportion of patients who went on to have a stone-related procedure within 90 days ranged from approximately 15% to 27%, depending on imaging type. Compared with patients who underwent CT imaging in the ED, those who underwent only US imaging were more likely to get CT scans after the ED visit. Those with only US imaging in the ED were even more likely to receive a CT evaluation if a stone procedure was performed.

“Many people do not go on to need a procedure for stone treatment, and thereby many may not ultimately need a CT scan for treatment planning if ultrasound is safe for initial imaging in the ED,” Dr Harper told Renal & Urology News. “In this context, national data show that ultrasound is still underutilized for reducing ionizing radiation, especially considering that stone forming patients are expected to have future ionizing radiation exposure over the course of the diagnosis and treatment of recurrent stone episodes.” 

For the study, Dr Harper’s team analyzed 2007–2015 data from MarketScan, a private employer-based health insurance database. The study population was 58.26% male and 41.74% female. Male and female patients had mean ages of 45.77 and 42.03 years, respectively. Data showed that 3.63%, 2.17%, and 4% of patients had undergone CT imaging within 30, 31–90, and 90–180 days, respectively, of presentation to the ED for acute renal colic.

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Chang HC, Dai JC, Holt SK, et al. national imaging trends for acute kidney stone disease: Do renal ultrasounds for nephrolithiasis in the emergency department pave the way to computerized tomography? Data presented in poster format at the American Urological Association 2018 annual meeting, San Francisco, May 18–21. Abstract MP50-20.