title: Eighteen-year experience with the Medstone STS lithotripter: safety, efficacy, and evolving practice patterns.
abstract: OBJECTIVE
  To evaluate trends in safety, efficacy, and practice patterns for shockwave lithotripsy (SWL) procedures performed during a 18-year period and correlate the findings with recent evidence-based practice guidelines.
  
  
  METHODS
  From January 1988 to June 2006, 66,819 SWLs were performed using the Medstone STS lithotripter in patients with radiologic evidence of stones in the kidney or ureter. Treatment characteristics, such as stone location and size, need of re-treatment, and final success rate were recorded. The procedures were further divided by year for statistical consideration. Statistical analysis was performed using Student t test; P < 0.05 was considered significant.
  
  
  RESULTS
  Overall SWL success rate was 85% (39,667/46,669), and the overall re-treatment rate was 7.2% (3,417/46,669). There was no significant change in the overall proportion of lower-pole calculi managed with SWL, although there was a significant decrease in the proportion of SWL used for lower calix stones larger than 16 mm in the time period after 2000 (P = 0.006). There was a steady increase in the number of procedures performed for renal calculi in other locations per year, in particular for intrarenal calculi smaller than 20 mm. Intrarenal stones larger than 30 mm decreased as a proportion of procedures per year (P = 0.048) There was no significant change in the proportion of upper and distal ureteral stones managed, corresponding to a solid plateau in the percentage of SWL performed per year.
  
  
  CONCLUSIONS
  Our study did not demonstrate an overall drop in SWL; however, it did show the interference of endoscopic procedures on two case scenarios. There was a significant decrease (P = 0.048) in SWL for renal stones larger than 30 mm, and the same trend was noted for lower calix stones larger than 15 mm (P = 0.06).
authors.affiliation: Department of Urology, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Renato Nardi
authors.initials: RN
authors.lastname: Pedro
authors.forename: Courtney
authors.initials: C
authors.lastname: Lee
authors.forename: Derek
authors.initials: D
authors.lastname: Weiland
authors.forename: Roland
authors.initials: R
authors.lastname: Ugarte
authors.forename: Katie
authors.initials: K
authors.lastname: Willihnganz
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
mesh_terms: D017677:Age Distribution; D004869:Equipment Safety; D019317:Evidence-Based Medicine; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000628:therapy; D008096:Lithotripsy / Q000295:instrumentation*; D010818:Practice Patterns, Physicians'; D012189:Retrospective Studies; D016896:Treatment Outcome; D014514:Ureteral Calculi / Q000628:therapy