LAUSR

OBJECTIVES To describe trends in computed tomography (CT) use and estimate the radiation exposure among stone formers using a national insurance claims database. METHODS Within MarketScan®, adult stone patients from 2007-2013 were identified using ICD-9, ICD-10, and CPT codes. Patients were classified as "active" (≥ 2 diagnosis codes for nephrolithiasis, or receipt of stone surgery) or "inactive" (one stone diagnosis) and compared to age- and gender- matched controls. CT utilization was tracked over 3 years for each group. Annual CT-related radiation exposure was estimated using previously published dose values and compared using Kruskal-Wallis and χ2 tests. Demographic factors associated with greater CT exposure were identified on multivariate logistic regression. RESULTS Of active stone patients, 112,140 underwent surgery and 215,376 were managed non-operatively. There were 175,228 inactive stone patients and 502,744 controls. On average, active stone patients received nearly ten times as many CTs as controls at 3 years (p<0.001), and more acute imaging (p<0.001). 25% and 15% of operative and non-operative patients, respectively, received ≥3 CTs in 3 years. This was associated with female gender. For non-operative patients, this was also associated with age, residence in the North-Central or South regions, and inversely associated with metropolitan residence (all p<0.01). Over 10% of active stone patients are estimated to receive >20 mSv in the first year alone. CONCLUSIONS CT use and non-surgical radiation exposure for active stone patients is significant. Over 10% are estimated to exceed occupational limits in the first year. Judicious CT imaging and low dose protocols are critical for stone patients.