PD37-03: Determining the threshold of safety for intrarenal pressure during flexible ureteroscopy using an in vivo pig model

Matthew Lee*, Chicago, IL, Deepak Agarwal, Minneapolis, MN, Bret Connors, Indianapolis, IN, Mark Assmus, Chicago, IL, James Williams, Tim Large, Indianapolis, IN, Amy Krambeck, Chicago, IL

Introduction: Ureteroscopy (URS) is the most commonly performed surgery for kidney stones.  Multiple studies have investigated what intrarenal pressures (IRPs) occur during URS.  However, no one has attempted to identify a threshold for IRP, that if exceeded, will result in renal parenchymal damage.  Herein, we attempted to identify this IRP safety threshold by subjecting in vivo porcine kidneys to various levels of pressurized irrigation.

Methods: 10 female pigs (60-80 kg) were intubated and sedated. The abdomen was opened with electrocautery and the ureters were isolated and opened. We inserted a LithoVue (Boston Scientific) ureteroscope into the ureter and advanced it up to the kidney. An 0-silk tie was then used to tie the ureter around the scope to create a closed system so we could subject the kidney to a maximum level of pressure. Realtime IRPs were measured using the Comet Pressure Wire (Boston Scientific).  Kidneys were subjected to various levels of pressure (0, 50, 100, and 150mmHg) for 36 minutes (based on published mean URS times). The control arm had 3 kidneys and each pressure group had 5 kidneys. Kidneys were then fixed using an intravascular perfusate and harvested.  Two expert pathologists then independently analyzed kidney slides (H&E staining and picrosirius red) to identify areas of renal damage.

Results: The differences in mean IRPs between the groups was significant (p < 0.0001). Two kidneys were exposed to IRPs > 185mmHg as we initially planned to have a 300mHg group. We identified that IRPs greater than 185mmHg routinely resulted in forniceal rupture.  Kidneys subjected to pressures > 185mmHg developed large areas of hematoma.  We did not find any differences in renal parenchymal damage

Conclusions: No differences in renal parenchymal damage were identified between pressure groups of 50, 100, or 150 mmHg.  However, IRPs > 185mmHg did result in forniceal rupture.

Source of Funding: Boston Scientific