Endourology & Stone Disease(구연) (E-165) 역행성 신장내 수술에서 요관 내시경 확장기 삽입이 어려운 환자에서 하부 요관각이 미치는 영향 1. 서울대학교 의과대학 비뇨의학교실 2. 가톨릭대학교 의과대학 비뇨의학교실 정규환¹, 조성용¹*, 양승훈¹, 이동섭²* Purpose: We aimed to investigate whether the angle created by the most lateral portion of the lower ureter is responsible for the difficulty in ureteral access sheath insertion. Materials and Methods: All male patients scheduled to undergo flexible ureteroscopy were enrolled. Patients with ureteral stricture in any course of the ureter and patients with problems at the ureteral opening were excluded. We set the coordinates of the most lateral portion of the lower ureter as M (x, y, z) using computed tomography. The bladder outlet was marked as the zero point O (0, 0, 0). The vector that passed through the urethra and point O was expressed as Vuo (0, 0, -u). The vector that passed through points O and M was expressed as Vom (x, y, z). Thus, an angle (90°- α) could be calculated between Vuo and Vom by using the rotation angle formula. Results: A total of 671 male patients were enrolled, among whom the ureteral access sheath could not pass through the most lateral portion of the lower ureter in 14 patients. The mean values of the α angle were 38.56° and 48.48° in the patient and control groups, respectively, compared with the 42 age- and sex-matched control subjects (p<0.001). Conclusions: The ureteral angle determined by the level of the bladder outlet and the most lateral portion of the lower ureter could be a causative factor for the failure of ureteral access sheath insertion. keywords : Ureter, Ureteroscopy, Tomography