title: After urgent drainage of an obstructed kidney by internal ureteric stenting; is ureteroscopic stone extraction always needed?
abstract: OBJECTIVE
  To assess the probability of spontaneous stone passage and its predictors after drainage of obstructed kidney by JJ stent, as insertion of an internal ureteric stent is often used for renal drainage in cases of calcular ureteric obstruction.
  
  
  METHODS
  Between January 2011 and June 2013, patients for whom emergent drainage by ureteric stents were identified. The patients' demographics, presentation, and stone characteristics were reviewed. The primary endpoint for this study was stone-free status at the time of stent removal, where all patients underwent non-contrast spiral computed tomography (NCCT) before stent removal. Ureteroscopic stone extraction was performed for CT detectable ureteric stones at the time of stent removal. Potential factors affecting the need for ureteroscopic stone extraction at the time of stent removal were assessed using univariate and multivariate statistical analyses.
  
  
  RESULTS
  Emergent ureteric stents were undertaken in 196 patients (112 males, 84 females) with a mean (SD) age of 53.7 (16.2) years, for renal obstruction drainage. At the time of stent removal, 83 patients (42.3%) were stone free; with the remaining 113 patients (57.7%) undergoing ureteroscopic stone extraction. On multivariate analysis, stone width [odds ratio (OR) 15.849, 95% confidence interval (CI) 2.83; P = 0.002) and radio-opaque stones (OR 12.035, 95% CI 4.65; P < 0.001) were independent predictors of the need for ureteroscopic stone extraction at the time of stent removal.
  
  
  CONCLUSIONS
  Spontaneous ureteric stone passage is possible after emergent drainage of an obstructed kidney by ureteric stenting. Stone opacity, larger stone width, and positive preoperative urine culture are associated with a greater probability of requiring ureteroscopic stone extraction after emergent drainage by ureteric stenting.
authors.affiliation: Urology and Nephrology Centre, Mansoura University, Egypt.
authors.forename: Diaa-Eldin
authors.initials: DE
authors.lastname: Taha
authors.affiliation: Urology and Nephrology Centre, Mansoura University, Egypt.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Elshal
authors.affiliation: Urology and Nephrology Centre, Mansoura University, Egypt.
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Zahran
authors.affiliation: Urology and Nephrology Centre, Mansoura University, Egypt.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Harraz
authors.affiliation: Urology and Nephrology Centre, Mansoura University, Egypt.
authors.forename: Ahmed R
authors.initials: AR
authors.lastname: El-Nahas
authors.affiliation: Urology and Nephrology Centre, Mansoura University, Egypt.
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Shokeir
keywords: BMI, body mass index; Drainage; Emergency; MSUC, midstream urine culture; NCCT, non-contrast spiral CT; OR, odds ratio; PCN, percutaneous nephrostomy; ROC, Receiver operating characteristic; SIRS, systemic inflammatory response syndrome; URS, ureteroscopy; Ureteric calculi; Ureteric stent; Ureteroscopy