title: Stone Attenuation Values Measured by Average Hounsfield Units and Stone Volume as Predictors of Total Laser Energy Required During Ureteroscopic Lithotripsy Using Holmium:Yttrium-Aluminum-Garnet Lasers.
abstract: OBJECTIVE
  To evaluate the predictors of the total laser energy (TLE) required during ureteroscopic lithotripsy (URS) using the holmium:yttrium-aluminum-garnet (Ho:YAG) laser for a single ureteral stone.
  
  
  METHODS
  We retrospectively analyzed the data of 93 URS procedures performed for a single ureteral stone in our institution from November 2011 to September 2015. We evaluated the association between TLE and preoperative clinical data, such as age, sex, body mass index, and noncontrast computed tomographic findings, including stone laterality, location, maximum diameter, volume, stone attenuation values measured using average Hounsfield units (HUs), and presence of secondary signs (severe hydronephrosis, tissue rim sign, and perinephric stranding).
  
  
  RESULTS
  The mean maximum stone diameter, volume, and average HUs were 9.2 ± 3.8 mm, 283.2 ± 341.4 mm3, and 863 ± 297, respectively. The mean TLE and operative time were 2.93 ± 3.27 kJ and 59.1 ± 28.1 minutes, respectively. Maximum stone diameter, volume, average HUs, severe hydronephrosis, and tissue rim sign were significantly correlated with TLE (Spearman's rho analysis). Stepwise multiple linear regression analysis defining stone volume, average HUs, severe hydronephrosis, and tissue rim sign as explanatory variables showed that stone volume and average HUs were significant predictors of TLE (standardized coefficients of 0.565 and 0.320, respectively; adjusted R2= 0.55, F = 54.7, P <.001).
  
  
  CONCLUSIONS
  Stone attenuation values measured by average HUs and stone volume were strong predictors of TLE during URS using Ho:YAG laser procedures.
authors: Department of Urology, Kouseiren Takaoka Hospital, Takaoka, Toyama, Japan. Electronic address: ofude_m@yahoo.co.jp.
authors: Mitsuo
authors: M
authors: Ofude
authors: Department of Urology, Toyama Prefectural Central Hospital, Toyama, Japan.
authors: Takashi
authors: T
authors: Shima
authors: Department of Urology, Kouseiren Takaoka Hospital, Takaoka, Toyama, Japan.
authors: Satoshi
authors: S
authors: Yotsuyanagi
authors: Department of Urology, Kouseiren Takaoka Hospital, Takaoka, Toyama, Japan.
authors: Daisuke
authors: D
authors: Ikeda
mesh_terms: D005260:Female; D005544:Forecasting; D006801:Humans; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D017602:Lithotripsy, Laser / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014514:Ureteral Calculi / Q000175:diagnosis / Q000601:surgery*; D018666:Ureteroscopy