title: Recurrence rate and risk factors for urinary calculi after extracorporeal shock wave lithotripsy.
abstract: OBJECTIVE
  We determined the recurrence rate after extracorporeal shock wave lithotripsy (ESWL*) and evaluated its associated risk factors, such as patient sex and age, volume of daily water intake, related diseases, family history of urinary calculi, number, burden and location of stones, residual stones after ESWL, serum uric acid level before ESWL and so forth.
  
  
  METHODS
  We conducted a retrospective study of 841 patients who underwent ESWL for primary treatment of urinary calculi between 1985 and 1987. Charts were reviewed for stone characteristics, outcomes and associated laboratory data. Followup 6 to 9 years later was done by mail and telephone interviews.
  
  
  RESULTS
  Followup data were available for 436 patients (52%). Overall, stones recurred in 51% of the 436 patients at a mean followup of 7.1 years. Late recurrences were common, and were noted in as many as 70% of the patients after 9 years. This rate is greater than what has been previously reported after other treatments. Cox regression analysis indicated that the major risk factors associated with recurrence were male gender (relative risk 1.406, p < 0.05) and multiple stones (relative risk 1.777, p < 0.05).
  
  
  CONCLUSIONS
  The frequent late recurrences support the speculation that ESWL might lead to greater recurrence rates. Therefore, the cost-effectiveness of ESWL versus other modalities for stone removal warrants more long-term evaluation.
authors.affiliation: Department of Surgery, Veterans General Hospital-Kaohsiung, Republic of China.
authors.forename: B Y
authors.initials: BY
authors.lastname: Sun
authors.forename: Y H
authors.initials: YH
authors.lastname: Lee
authors.forename: B P
authors.initials: BP
authors.lastname: Jiaan
authors.forename: K K
authors.initials: KK
authors.lastname: Chen
authors.forename: L S
authors.initials: LS
authors.lastname: Chang
authors.forename: K T
authors.initials: KT
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008096:Lithotripsy; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012008:Recurrence; D012044:Regression Analysis; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D014545:Urinary Calculi / Q000453:epidemiology / Q000628:therapy*