title: A comparison between an in vitro ureteroscopic stone size estimation and the stone size measurement with the help of a scale on stone baskets.
abstract: BACKGROUND
  Endoscopic treatment of ureter stones and renal calculi relies on the surgeon's estimation of the stone size for both lithotripsy and removal of stones or stone fragments. We therefore compared precision and reliability of the endoscopic estimation of stone size by the surgeon with measurements on a scale on a stone basket.
  
  
  METHODS
  Two surgeons (one high experienced and one low experienced) first estimated, then measured the size of 12 stones differing in size and color using different stone baskets (2.5, 3.0, 4.0 Ch) each via a semirigid renoscope in an artificial ureter under water repeatedly on two different days. All together, we had 288 measurements and 288 estimations.
  
  
  RESULTS
  On the whole, the accuracy of the estimation diminished with bigger stones. There is an increasing underestimation with increasing stone size. Factors, which significantly influence the estimation, are the operating surgeon, the color of the stone, the time sequence, and the size of the closed basket, which was held beside the stone. The accuracy of the measurement of the stone baskets is not as good as the estimation. The small 2.5-Ch basket is the most accurate in measuring big stones (>6 mm), the 3.5 Ch in intermediate stones (3-6 mm), the big basket (4.0 Ch) in small stones (<3 mm).
  
  
  CONCLUSIONS
  This first attempt at validation of a scale on stone baskets shows different results for each basket which could be systematically improved. Until now, the estimation of the surgeons is better than the measurement, but it is also influenced by factors like the surgeon or the color of the stone.
authors: Urology Clinic and Policlinic, University Medical Center Schleswig-Holstein (UKSH), Campus Lübeck, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany. drjcordes@yahoo.de.
authors: Jens
authors: http://orcid.org/0000-0003-3758-2078
authors: J
authors: Cordes
authors: Urology Clinic and Policlinic, University Medical Center Schleswig-Holstein (UKSH), Campus Lübeck, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany.
authors: Lisa
authors: L
authors: Teske
authors: Urology Clinic and Policlinic, University Medical Center Schleswig-Holstein (UKSH), Campus Lübeck, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany.
authors: Felix
authors: F
authors: Nguyen
authors: Urotech GmbH, Achenmuehle, Rohrdorf, Germany.
authors: Wolfhard
authors: W
authors: Pinkowski
authors: Urology Clinic and Policlinic, University Medical Center Schleswig-Holstein (UKSH), Campus Lübeck, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany.
authors: Karl-Dietrich
authors: KD
authors: Sievert
authors: Institute of Medical Biometry and Statistics, University Medical Center Schleswig-Holstein (UKSH), Campus Lübeck, University of Lübeck, Lübeck, Germany.|Center for Clinical Trials, University of Lübeck, Lübeck, Germany.
authors: Reinhard
authors: R
authors: Vonthein
mesh_terms: D003950:Diagnostic Techniques, Urological / Q000295:instrumentation; D061827:Dimensional Measurement Accuracy; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D014514:Ureteral Calculi / Q000473:pathology* / Q000601:surgery*; D018666:Ureteroscopy
keywords: Endourology; Stone basket; Stone size estimation