title: Single-center experience using three shockwave lithotripters with different generator designs in management of urinary calculi.
abstract: OBJECTIVE
  We retrospectively reviewed the treatment outcomes of extracorporeal shockwave lithotripsy (SWL) in a single center using either the Wolf Piezolith 2300 (a piezoelectric lithotripter), the Dornier MPL9000 (an electrohydraulic lithotripter), or the Dornier Compact Delta (an electromagnetic lithotripter) from January 1992 to June 2002.
  
  
  METHODS
  A series of 3123 (1449 Piezolith 2300, 780 MPL9000, and 894 Compact Delta) solitary radiopaque urinary stones of < or =15 mm receiving primary SWL were identified. "Stone free" was defined as the absence of evidence of stone on plain radiography. Treatment outcomes were assessed by the stone-free rate 3 months after one treatment session, the retreatment rate, the auxiliary procedure rate, the complication rate, and the effectiveness quotient (EQ). In order to have a better assessment of the efficacy of individual lithotripters, multiple logistic regression was performed to control various factors affecting treatment outcomes, including lithotripter-type, patients' sex and age, history of previous SWL, the stone characteristics (side, site, and size), and the presence of a stent or nephrostomy tube.
  
  
  RESULTS
  There were significant differences in the stone site distribution and mean stone size among the three groups. The overall EQ for the Piezolith 2300, MPL9000, and Compact Delta were 0.345, 0.303, and 0.257, respectively. However, using the multiple logistic regression model, the adjusted odds ratio (AOR) of a patient being stone-free after 3 month for the Piezolith 2300 and MPL9000 (using the Compact Delta as the referent category) were 1.38 (95% CI 1.15, 1.65) and 1.72 (95% CI 1.39, 2.11), respectively. Patients treated using the MPL9000 had significantly less re-treatment (AOR = 0.57; 95% CI 0.48, 0.69) than the other groups. No significant difference in the auxiliary procedure rate and complication rate for the three machines was observed.
  
  
  CONCLUSIONS
  Based on multivariate analysis results, the Dornier MPL9000 had the best treatment outcomes in terms of stone-free rate and re-treatment rate among the three lithotripters.
authors.affiliation: Scottish Lithotriptor Centre, Western General Hospital, Edinburgh, UK.
authors.forename: C F
authors.initials: CF
authors.lastname: Ng
authors.forename: T J
authors.initials: TJ
authors.lastname: Thompson
authors.forename: L
authors.initials: L
authors.lastname: McLornan
authors.forename: D A
authors.initials: DA
authors.lastname: Tolley
mesh_terms: D055590:Electromagnetic Phenomena / Q000295:instrumentation; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008096:Lithotripsy / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome; D014545:Urinary Calculi / Q000000981:diagnostic imaging / Q000628:therapy*; D014567:Urography