title: Predictors of fluoroscopy time during percutaneous nephrolithotomy: impact of postgraduate urology trainees and S.T.O.N.E. nephrolithometry score.
abstract: OBJECTIVE
  To determine predictors of fluoroscopy time (FT) during percutaneous nephrolithotomy (PCNL) and assess the impact of urology postgraduate trainees (PGTs) and S.T.O.N.E. nephrolithometry score.
  
  
  METHODS
  A retrospective review of patients undergoing PCNL between 2010 and 2013 at a tertiary healthcare center was performed. Patients' demographics, stone characteristics, including S.T.O.N.E. nephrolithometry score, and operative data were compared among PGTs. Predictors of FT were determined using univariate and multivariate models.
  
  
  RESULTS
  A total of 103 PCNLs were assisted by 10 PGTs from postgraduate years (PGYs) 4 and 5 (37 [35.9%] and 66 [64.1%] cases, respectively). Sixty percent of patients were males with a mean age of 55.2±1.5 years and a mean body mass index of 26.4±0.5 kg/m(2). The mean S.T.O.N.E. score was 7.7±0.1, with tubeless PCNL in 53 (51.5%) cases. The mean FT was 120±5 seconds, mean operative time was 102±3.5 minutes, and mean length of hospital stay was 4.2±0.34 days. The overall stone-free rate was 72.8%. PGY-5 trainees used significantly less FT than PGY-4 trainees (115±6 seconds vs 130±7 seconds; p=0.04). FT significantly correlated with the number of involved calices (r=0.24; p=0.02), number of punctures (r=0.6; p=0.01), number of tracts (r=0.4; p=0.01), and operative time (r=0.4; p=0.01). In addition, cases with estimated blood loss (EBL) <250 mL were associated with significantly less FT than those with blood loss >250 mL (109±5.1 seconds vs 148.2±10.9 seconds; p=0.001). On multivariate analysis, the number of punctures, EBL, and operative time were found to be independent predictors for FT. However, there was no correlation of FT with the S.T.O.N.E. nephrolithometry score (r=0.16; p=0.1).
  
  
  CONCLUSIONS
  The number of punctures, EBL, and operative time were the only independent predictors of prolonged FT during PCNL.
authors.affiliation: 1 Division of Urology, McGill University Health Centre , Montreal, Québec, Canada .
authors.forename: Yasser Abdelsattar
authors.initials: YA
authors.lastname: Noureldin
authors.forename: Mohamed Aly
authors.initials: MA
authors.lastname: Elkoushy
authors.forename: Sero
authors.initials: S
authors.lastname: Andonian
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016063:Blood Loss, Surgical / Q000706:statistics & numerical data; D015331:Cohort Studies; D004503:Education, Medical, Graduate; D005260:Female; D005471:Fluoroscopy / Q000706:statistics & numerical data*; D006801:Humans; D007669:Kidney Calculi / Q000601:surgery*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009403:Nephrostomy, Percutaneous / Q000706:statistics & numerical data*; D061646:Operative Time; D012189:Retrospective Studies; D013997:Time Factors; D014572:Urology / Q000193:education*; D055815:Young Adult