title: Stone volume is best predictor of operative time required in retrograde intrarenal surgery for renal calculi: implications for surgical planning and quality improvement.
abstract: Retrograde intrarenal surgery (RIRS) is highly successful at eliminating renal stones of various sizes and compositions. As urologists are taking on more complex procedures using RIRS, this has led to an increase in operative (OR) times. Our objective was to determine the best predictor of OR time in patients undergoing RIRS. We retrospectively reviewed the records of patients undergoing unilateral RIRS for solitary stones over a 10 year time span. Stones were fragmented and actively extracted using a basket. Variables potentially affecting OR time such as patient age, sex, BMI, lower pole stone location, volume, Hounsfield units (HU), composition, ureteral access sheath (UAS) use, and pre-operative stenting were collected. Multivariable linear and stepwise regression was used to evaluate the predictors of OR time. There were 118 patients that met inclusion criteria. The median stone volume was 282.6 mm3(IQR 150.7-644.7) and the mean OR time was 50 min (±25.9 SD). On univariate linear regression, stone volume had a moderate correlation with OR time (y = 0.022x + 38.2, r2= 0.363, p < 0.01). On multivariable stepwise regression, stone volume had the strongest impact on OR time, increasing time by 2.0 min for each 100 mm3increase in stone volume (p < 0.001). UAS added 13.5 (SE 3.9, p = 0.001) minutes and renal lower pole location added 9 min (SE 4.3, p = 0.03) in each case they were used. Pre-operative stenting, HU, calcium oxalate stone composition, sex, and age had no significant effect on OR time. Amongst the main stone factors in RIRS, stone volume has the strongest impact on operative time. This can be used to predict the length of the procedure by roughly adding 2 min per 100 mm3increase in stone volume.
authors.affiliation: Division of Urology, Albany Medical College, 43 New Scotland Ave, Albany, NY, 12208, USA. igsorokin@gmail.com.
authors.forename: Igor
authors.initials: I
authors.lastname: Sorokin
authors.affiliation: Division of Urology, Albany Medical College, 43 New Scotland Ave, Albany, NY, 12208, USA.
authors.forename: Diana K
authors.initials: DK
authors.lastname: Cardona-Grau
authors.affiliation: Division of Urology, Albany Medical College, 43 New Scotland Ave, Albany, NY, 12208, USA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rehfuss
authors.affiliation: Department of Radiology, Albany Medical College, Albany, NY, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Birney
authors.affiliation: Department of Radiology, Albany Medical College, Albany, NY, USA.
authors.forename: Costas
authors.initials: C
authors.lastname: Stavrakis
authors.affiliation: Division of Urology, Albany Medical College, 43 New Scotland Ave, Albany, NY, 12208, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Leinwand
authors.affiliation: Department of Radiology, Albany Medical College, Albany, NY, USA.
authors.forename: Allen
authors.initials: A
authors.lastname: Herr
authors.affiliation: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Feustel
authors.affiliation: Division of Urology, Albany Medical College, 43 New Scotland Ave, Albany, NY, 12208, USA.|Urological Institute of Northeastern New York, Albany, NY, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: White
mesh_terms: D005260:Female; D005544:Forecasting; D006801:Humans; D007669:Kidney Calculi / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D058996:Quality Improvement; D012189:Retrospective Studies; D018666:Ureteroscopy / Q000379:methods*
keywords: Operative time; Renal stones; Stone volume; Ureteroscopy