title: Optimal Skin-to-Stone Distance Is a Positive Predictor for Successful Outcomes in Upper Ureter Calculi following Extracorporeal Shock Wave Lithotripsy: A Bayesian Model Averaging Approach.
abstract: OBJECTIVE
  To investigate whether skin-to-stone distance (SSD), which remains controversial in patients with ureter stones, can be a predicting factor for one session success following extracorporeal shock wave lithotripsy (ESWL) in patients with upper ureter stones.
  
  
  METHODS
  We retrospectively reviewed the medical records of 1,519 patients who underwent their first ESWL between January 2005 and December 2013. Among these patients, 492 had upper ureter stones that measured 4-20 mm and were eligible for our analyses. Maximal stone length, mean stone density (HU), and SSD were determined on pretreatment non-contrast computed tomography (NCCT). For subgroup analyses, patients were divided into four groups. Group 1 consisted of patients with SSD<25th percentile, group 2 consisted of patients with SSD in the 25th to 50th percentile, group 3 patients had SSD in the 50th to 75th percentile, and group 4 patients had SSD≥75th percentile.
  
  
  RESULTS
  In analyses of group 2 patients versus others, there were no statistical differences in mean age, stone length and density. However, the one session success rate in group 2 was higher than other groups (77.9% vs. 67.0%; P = 0.032). The multivariate logistic regression model revealed that shorter stone length, lower stone density, and the group 2 SSD were positive predictors for successful outcomes in ESWL. Using the Bayesian model-averaging approach, longer stone length, lower stone density, and group 2 SSD can be also positive predictors for successful outcomes following ESWL.
  
  
  CONCLUSIONS
  Our data indicate that a group 2 SSD of approximately 10 cm is a positive predictor for success following ESWL.
authors.affiliation: Department of Urology, Gangnam Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Kang Su
authors.initials: KS
authors.lastname: Cho
authors.affiliation: Department of Urology, Incheon Red Cross Hospital, Incheon, Korea.
authors.forename: Hae Do
authors.initials: HD
authors.lastname: Jung
authors.affiliation: Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Won Sik
authors.initials: WS
authors.lastname: Ham
authors.affiliation: Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Doo Yong
authors.initials: DY
authors.lastname: Chung
authors.affiliation: Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yong Jin
authors.initials: YJ
authors.lastname: Kang
authors.affiliation: Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Won Sik
authors.initials: WS
authors.lastname: Jang
authors.affiliation: Department of Urology, Severance Check-Up, Yonsei University Health System, Seoul, Korea.
authors.forename: Jong Kyou
authors.initials: JK
authors.lastname: Kwon
authors.affiliation: Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Young Deuk
authors.initials: YD
authors.lastname: Choi
authors.affiliation: Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Joo Yong
authors.initials: JY
authors.lastname: Lee
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001499:Bayes Theorem; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000000981:diagnostic imaging / Q000628:therapy*; D008096:Lithotripsy; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012189:Retrospective Studies; D012737:Sex Factors; D012867:Skin / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed