title: Influence of ureteral stone components on the outcomes of electrohydraulic lithotripsy.
abstract: OBJECTIVE
  We evaluated the influence of urinary stone components on the outcomes of ureteroscopic removal of stones (URS) by electrohydraulic lithotripsy (EHL) in patients with distal ureteral stones.
  
  
  METHODS
  Patients with a single distal ureteral stone with a stone size of 0.5 to 2.0 cm that was completely removed by use of EHL were included in the study. Operating time was defined as the time interval between ureteroscope insertion and complete removal of ureteral stones. Ureteral stones were classified into 5 categories on the basis of their main component (that accounting for 50% or more of the stone content) as follows: calcium oxalate monohydrate (COM), calcium oxalate dihydrate, carbonate apatite (CAP), uric acid (UA), and struvite (ST).
  
  
  RESULTS
  A total of 193 patients (131 males and 62 females) underwent EHL. The mean operating time was 25.1±8.2 minutes and the mean stone size was 1.15±0.44 cm. Calcium oxalate stones accounted for 64.8% of all ureteral stones, followed by UA (19.7%), CAP (8.3%), and ST (7.2%) stones. The mean operating time was significantly longer in the UA group (28.6±8.3 minutes) than in the COM group (24.0±7.8 minutes, p=0.04). In multivariate analyses, the stone size was negatively associated with the odds ratio (OR) for successful fragmentation. UA as a main component (OR, 0.42; 95% confidence interval, 0.20 to 0.89; p=0.023) was also found to be significantly important as a negative predictive factor of successful fragmentation after adjustment for stone size.
  
  
  CONCLUSIONS
  The results of the present study suggest that successful fragmentation by URS with EHL could be associated with the proportion of the UA component.
authors.affiliation: Department of Urology, Hallym University College of Medicine, Seoul, Korea.
authors.forename: Hyeong Cheol
authors.initials: HC
authors.lastname: Song
authors.forename: Ha Bum
authors.initials: HB
authors.lastname: Jung
authors.forename: Yong Seong
authors.initials: YS
authors.lastname: Lee
authors.forename: Young Goo
authors.initials: YG
authors.lastname: Lee
authors.forename: Ki Kyung
authors.initials: KK
authors.lastname: Kim
authors.forename: Sung Tae
authors.initials: ST
authors.lastname: Cho
keywords: Lithotripsy; Ureteroscopy; Uric acid; Urinary