title: Computed tomography versus ureteroscopy in identification of renal tract stone with ureteral stent in situ.
abstract: BACKGROUND
  The aim of this study was to validate the use of non-contrast computed tomography (CT) with a ureteral stent in situ instead of ureteroscopy for identification of renal tract stones.
  
  
  METHODS
  All patients who had stents inserted for renal tract stones and underwent  non-contrast CT with the stent in situ followed by ureteroscopy between May 2008 and October 2009 at The Canberra hospital, Australia, were analysed retrospectively. Statistical analysis was performed to compare any differences between CT and ureteroscopy in the identification of stones.
  
  
  RESULTS
  Overall, 57 patients were included in the study. The difference between CT and ureteroscopy findings was statistically significant. CT identification of stones with a stent in situ had a sensitivity of 86%, a specificity of 46%, a positive predictive value of 63%, a negative predictive  value of 76% and an accuracy of 67%.
  
  
  CONCLUSIONS
  Our study suggests that non-contrast CT is inferior to the 'gold standard' of ureteroscopy. It lacks sensitivity, specificity, positive predictive value, negative predictive value and accuracy. Therefore, we cannot recommend using non-contrast  CT to replace ureteroscopy.
authors: Canberra Hospital, Australia. vincetang@hotmail.com
authors: V C Y
authors: VC
authors: Tang
authors: A
authors: A
authors: Attwell-Heap
mesh_terms: D006801:Humans; D007669:Kidney Calculi / Q000175:diagnosis*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D015607:Stents; D036542:Tomography, Spiral Computed / Q000379:methods / Q000592:standards*; D014514:Ureteral Calculi / Q000175:diagnosis*; D018666:Ureteroscopy / Q000592:standards*