Category: Clinical Stones: Ureteroscopy

MP29-6 - Renal Pelvic Pressure during Ureteroscopy: Sheath versus Ureteroscope alone

Sun, Sep 23
2:00 PM - 4:00 PM

Introduction & Objective : Ureteroscopy (URS) requires irrigation for visualisation.  Renal pelvic pressures (RPP) can rise in URS to levels greater than the often accepted threshold of 30 cmH2O for pyelovenous and pyelolymphatic backflow, potentially increasing sepsis risk.  Ureteric access sheaths (UAS) facilitate renal drainage during URS thus lowering RPP.  We developed an instrumented platform to measure fluid pressures during URS in ex vivo pig kidneys with and without a UAS.

Methods :

Porcine kidneys and attached ureter were transported to the laboratory and experimentation begun within 2 hours of slaughter.  A 9.5Fr ureteroscope (Lithovue, Boston Scientific) inserted via the ureter into renal pelvis and if indicated a 11/13F UAS used (Navigator, Boston Scientific). RPP was measured via a pressure sensor wire (0.014in, Comet, Boston Scientific) introduced via the ureteroscope, and pressure at the URS inlet measured with a second fibre-optic pressure sensor (75-0714, FISO). Irrigant delivered via a 1L bag of normal saline 60cm above the kidney.  Saline boluses were delivered using a 10mL pumping system (SAPS, Boston Scientific).  Each experimental run began with filling until steady state RPP occurred.  Then three 10mL boluses were instilled over 2 seconds, followed by three boluses over 5 seconds and then three boluses over 10 seconds.   Then five 2mL boluses over 1 second.  Irrigation then stopped and the kidney passively drained. Pressures were measured continuously.

Results :

In total 36 experimental runs were performed on 10 kidneys: 21 with UAS, 15 without UAS.  Table 1 shows mean RPP measured across both groups. In all cases UAS use resulted in significantly lower RPP.

Conclusions : Safe RPP during URS has been proposed at <30cmH20. We developed an experimental platform allowing us to quantify pressure during URS.   In the absence of a UAS RPPs approach 30cmH20 at steady state and almost 60 cmH20 with bolus injection.  The addition of a UAS reduced steady state RPP to <14 cmH20 and during boluses pressure never exceeded 30 cmH20.  A caveat is that our model uses ex vivo porcine rather than in vivo human kidneys.  We acknowledge UAS have some potential risks however our data suggests UAS offer the benefit of halving RPP during URS.

Louise Rouse

Clinical Endourology Fellow
Oxford University Hospitals
Oxford, England, United Kingdom

Robin Cleveland

Professor of Engineering Science
Institute of Biomedical Engineering, The University of Oxford
Oxford, England, United Kingdom

Ben W. Turney

Bernard Senior Clinical Researcher in Urology
Nuffield Department of Surgical Sciences
Oxford, England, United Kingdom