Endourology & Stone Disease(구연) (E-156) Radiation Exposure To the Urology Surgeon During Retrograde Intrarenal Surgery 가천의대 길병원 비뇨의학과 박태영,박일우,박건현,윤상진,정한,김태범,정경진,오진규,김광택,김창희 BACKGROUND & OBJECTIVES Retrograde intrarenal surgery (RIRS) is a common procedure with a risk of radiation exposure for urologists, but studies about the radiation exposure or maximum permissible dose are limited. This study aimed to measure radiation exposure in urologists during RIRS, and estimated the number of safely-performed cases. This study also identified variables that affect radiation exposure to establish safe conditions. MATERIALS & METHODS The radiation exposure dose was measured at the eye, neck, chest, arm, and hands of a single urologist who performed 226 RIRS. The number of annually performed RIRS was estimated based on the annual permissible occupational exposure radiation dose guidelines of the National Council on Radiation Protection and Measurements. The radiation exposure dose was evaluated to determine their correlation with age, gender, patient body mass index, operation time, fluoroscopy screening time, tube voltage, tube current, stone numbers, stone burden, stone laterality, stone location, Hounsfield unit (HU) values of the renal calculi. RESULTS The mean duration of surgery was 83.2 min and fluoroscopy screening time was 5.13 min; the mean tube voltage and current were 68.88 kV and 2.48 mA, respectively. The cumulative radiation dose at the eye, neck, chest, right upper arm, left ring finger, and right ring finger were 65.53, 69.95, 131.79, 124.43, 165.66 and 126.64 mSv, respectively. Radiation reduction rates were 97% and 98% by a lead collar and apron, respectively. Considering annual permissible dose, 86 URS cases can be performed without a lead apron versus 2,568 cases with an apron; considering the permissible dose for the eyes and hands, 517 and 682 cases were possible. Significant correlations were observed between stone numbers (P = 0.00009), HU (P = 0.02730) and radiation exposure dose at eye, stone numbers (P = 0.00009), HU (P = 0.4580) and radiation exposure dose at chest, stone numbers (P = 0.00088), HU (P = 0.00184) and radiation exposure dose at chest effective, stone numbers (P = 0.00009), HU (P = 0.04630) and radiation exposure dose at right ring finger. CONCLUSION Considering radiation exposure risk, protective gear is necessary to ensure safety and efficacy of RIRS. Efforts to reduce radiation dose before and during surgery are required when renal calculi have large number of stones or large HU. keywords : nephrolithiasis renal calculi; radiation dosage; fluoroscopy