title: Flow matters 2: How to improve irrigation flow in small-calibre percutaneous procedures-the purging effect.
abstract: BACKGROUND
  Aim of this study was to investigate whether the combination of high-pressure irrigation inflow combined with simultaneous sensor-controlled suction could improve irrigation turnover without leading to high peak intrarenal pressure in small-calibre percutaneous instruments (SCPI). M + M: A MIP XS sheath (9.5 Fr. outer diameter and 8.5 Fr. inner diameter) and a 7.5-Fr. nephroscope (3-Fr. irrigation channel; MIP XS by Nagele, Karl Storz, Tuttlingen, Germany) was inserted into the collecting system of a non-perfused cadaveric porcine kidney, an 8-Fr. mono-J catheter was introduced through the ureter. Irrigation was performed using a pressure-controlled, combined irrigation/suction pump (Uromat E.A.S.I., Karl Storz, Tuttlingen, Germany) in either single-flow or continuous-flow (=combination of irrigation and suction) mode. Intrarenal pressure was measured and irrigation fluid turnover was measured by a cystometry catheter inserted trans-parenchymally into the renal pelvis. Pressure changes were recorded by a urodynamic workstation.
  
  
  RESULTS
  Applying pressure-controlled suction, irrigation fluid turnover could be increased by 5 % at an inflow pressure of 75 mmHg (80-84 ml/min) and 15 % at an inflow pressure of 110 mmHg (196-110 ml/min). Suction decreased the intrarenal pressure by 14 % at 75 mmHg (19-14.5 cm H2O) and 28 % at 110 mmHg inflow pressure (37-26.5 cm H2O).
  
  
  CONCLUSIONS
  Although combination of pressure irrigation with sensor-controlled suction increases irrigation flow in SCPI, the intrarenal pressure could be reduced with combined suction via a transurethral mono-J catheter. This irrigation method in percutaneous surgery is called purging effect.
authors.affiliation: Department of Urology and Andrology, General Hospital Hall in Tirol, Milser Str. 10, Hall i.T., 6060, Austria. prof@udonagele.at.
authors.forename: Udo
authors.initials: U
authors.lastname: Nagele
authors.affiliation: Department of Urology and Andrology, General Hospital Hall in Tirol, Milser Str. 10, Hall i.T., 6060, Austria.
authors.forename: Ute
authors.initials: U
authors.lastname: Walcher
authors.affiliation: Community Hospital Ebersberg, Ebersberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Bader
authors.affiliation: Hannover Medical School, Hannover, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Herrmann
authors.affiliation: University Hospital Tübingen, Tübingen, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kruck
authors.affiliation: University Hospital Frankfurt am Main, Frankfurt am Main, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Schilling
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004867:Equipment Design; D007674:Kidney Diseases / Q000628:therapy*; D009403:Nephrostomy, Percutaneous / Q000295:instrumentation*; D011182:Postoperative Care / Q000379:methods*; D013552:Swine; D007507:Therapeutic Irrigation; D018666:Ureteroscopy / Q000295:instrumentation*; D014563:Urodynamics / Q000502:physiology*
keywords: Intrarenal pressure; Irrigation flow; Microperc; Minimally invasive percutaneous stone treatment (MIP); Purging effect