Frecuencia y factores predictores para ureteroscopía en blanco, estudio prospectivo observacional. Hospital Clínico Universidad de Chile 2016-2019

Introduction: ureteroscopy today is the preferred therapeutic option for the treatment of ureteral lithiasis. The absence of lithiasis during the intraoperative; that is, spontaneous elimination prior to the intervention, it is described in 13.7% in international reports. In this study, the blank ureteroscopy rate was determined at the “Hospital Clínico Universidad de Chile”, as well as associated risk factors.Methodology: patients with a history of prior renal colic and computed tomography (CT) of ureteral lithiasis, with surgical indication, who underwent semi-rigid ureteroscopy in a center, between 2016-2019, were included. Data related to the size, location and density of the lithiasis were collected through a form, as well as the time of symptoms, date of tomography prior to surgery and the presence or absence of lithiasis during the intervention. Categorical variables were analyzed through Chi-square test and continuous with Student's T-test.Results: from a total of 156 patients, 24 (15.4 %) resulted in negative ureteroscopy. There was no statistic difference regarding age, gender or localization of the stone. We could determine two risk factors: 26% concerning the size of the stone, <7mm (p=0.017), and 23% as for the interval since the last CT taken, >30 days (p=0.006), increasing the risk of the group with both factors up to 35% (p=0.009).Conclusions: according to our results, an <30 days updated, CT scan its fundamental in the preoperative study of <7mm ureteral stone in order to reduce the risk of negative ureteroscopy