title: Clearance of Stone Fragments and Stone Dust by Continuous Flow Hydrodynamics in Percutaneous Renal Surgery: An In Vitro Study.
abstract: OBJECTIVE
  To investigate the capacity of stone clearance in common percutaneous nephrolithotomy (PCNL) systems achieved solely by hydrodynamic effects in an in vitro setting.
  
  
  METHODS
  A watertight cylindrical cast with a caliceal void served as an in vitro model. Various instruments for percutaneous renal surgery working with both continuous flow (fCF) and open Rutner sidearm (fCO) were tested. The model was loaded with standardized artificial stone material (2 mm in diameter) to examine stone removal by the vacuum cleaner effect and with sand (0.1-0.5 mm in diameter) to measure the washout effect caused by irrigation backflow. The association between washout of gravel and irrigation pressure was analyzed using ANOVA. Regression analysis was performed to assess the influence of the instruments' hydrodynamic characteristics-effective cross section of the outflow and irrigation flow volume.
  
  
  RESULTS
  Provoking the vacuum cleaner effect removal of stones was only effective in fCF but not in fCO instruments. Depending on irrigation pressure, the volumetric flow rate and effective cross section of the outflow clearance of sand could be observed in various medium- and large-sized fCF and fCO instruments, whereas in small-sized systems, clearance effects were negligible. Regression analysis showed clearance of stone dust strongly associated with an instrument's volumetric flow rate.
  
  
  CONCLUSIONS
  This in vitro study demonstrated that the application of medium- and large-sized fCF PCNL systems removes both "insignificant" stones and dust solely by hydrodynamic effects. Further studies have to show if these effects also occur in the in vivo situation.
authors.affiliation: 1 Department of Urology and Pediatric Urology, University Hospital Frankfurt , Frankfurt, Germany .
authors.forename: Rene
authors.initials: R
authors.lastname: Mager
authors.affiliation: 2 ExperTeach GmbH , Dietzenbach, Germany .
authors.forename: Christopher
authors.initials: C
authors.lastname: Balzereit
authors.affiliation: 1 Department of Urology and Pediatric Urology, University Hospital Frankfurt , Frankfurt, Germany .
authors.forename: Tanja
authors.initials: T
authors.lastname: Hüsch
authors.affiliation: 3 Department of Urology and Urologic Oncology, Hannover Medical School , Hannover, Germany .
authors.forename: Thomas
authors.initials: T
authors.lastname: Herrmann
authors.affiliation: 4 Department of Urology and Andrology, General Hospital Hall , Hall in Tyrol, Austria .
authors.forename: Andre
authors.initials: A
authors.lastname: Nicklas
authors.affiliation: 4 Department of Urology and Andrology, General Hospital Hall , Hall in Tyrol, Austria .
authors.forename: Udo
authors.initials: U
authors.lastname: Nagele
authors.affiliation: 1 Department of Urology and Pediatric Urology, University Hospital Frankfurt , Frankfurt, Germany .
authors.forename: Axel
authors.initials: A
authors.lastname: Haferkamp
authors.affiliation: 1 Department of Urology and Pediatric Urology, University Hospital Frankfurt , Frankfurt, Germany .|5 Department of Urology, Isarkliniken Munich , Munich, Germany .
authors.forename: David
authors.initials: D
authors.lastname: Schilling
mesh_terms: D006801:Humans; D057446:Hydrodynamics; D007669:Kidney Calculi / Q000601:surgery*; D009403:Nephrostomy, Percutaneous; D011312:Pressure; D007507:Therapeutic Irrigation