title: Preoperative factors predicting spontaneous clearance of residual stone fragments after flexible ureteroscopy.
abstract: OBJECTIVE
  To investigate factors predicting spontaneous clearance of residual renal fragments after flexible ureteroscopy.
  
  
  METHODS
  Among 546 patients who underwent lithotripsy with flexible ureteroscopy, 81 had residual renal fragments, as determined by kidney-ureter-bladder films on postoperative day 1. The final outcome was determined at 3 months after the last flexible ureteroscopy session using non-contrast computed tomography. Patient characteristics and preoperative factors were analyzed using the unpaired t-test and χ(2)-test. Correlations between the possible predictive factors and the spontaneous clearance of residual renal fragments after flexible ureteroscopy were analyzed using a multivariate logistic regression model with backward selection.
  
  
  RESULTS
  Non-contrast computed tomography at postoperative month 3 showed that 33 cases (40.7%) had spontaneous clearance of residual renal fragments, whereas 48 (59.3%) showed non-clearance. Significant differences were found between these cases in terms of stone number, stone location, presence of lower pole calculi and preoperative stent placement. Multivariate assessment showed that stone number (P = 0.004), presence of lower pole calculi (P = 0.021) and presence of hydronephrosis (P = 0.024) were independent predictors of the spontaneous clearance of residual renal fragments after flexible ureteroscopy.
  
  
  CONCLUSIONS
  Stone number, presence of lower pole calculi and presence of hydronephrosis are independent predictive factors of the spontaneous clearance of residual renal fragments after flexible ureteroscopy.
authors.affiliation: Department of Urology, Ohguchi East General Hospital, Yokohama, Kanagawa, Japan; Department of Urology, Yokohama City University Graduate School of Medicine, Yokohama, Kanagawa, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ito
authors.forename: Shinnosuke
authors.initials: S
authors.lastname: Kuroda
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawahara
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Makiyama
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yao
authors.forename: Junichi
authors.initials: J
authors.lastname: Matsuzaki
mesh_terms: D000368:Aged; D019540:Area Under Curve; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000209:etiology; D007669:Kidney Calculi / Q000000981:diagnostic imaging / Q000473:pathology* / Q000628:therapy*; D007670:Kidney Calices; D008096:Lithotripsy; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D012372:ROC Curve; D011859:Radiography; D012075:Remission, Spontaneous; D012189:Retrospective Studies; D015607:Stents; D016896:Treatment Outcome; D018666:Ureteroscopy
keywords: computed tomography; helical; kidney stone; lithotripsy; multivariate analysis; ureteroscopy