Does instrumentation and irrigation configuration affect intrarenal pressure during PCNL?

Objectives: To measure the effects of varying configurations of nephroscope sheath, irrigation, instruments, and suction on intrarenal pressure (IRP) during percutaneous nephrolithotomy (PCNL). Materials and Methods: Kidney and ureter 3D printed models from a deidentified patient's CT scan were placed in a plaster and foam mould, simulating the torso of a prone patient. An Amplatz sheath was inserted into the kidney model. Fourteen different rigid nephroscope sheath (RNS), irrigation, instrument and suction configurations were compared. IRP was measured in a retrograde fashion. Comparisons were performed using the Wilcoxon Signed-Rank test followed by Bonferroni correction. Results: The mean IRP with and without the RNS was 19.1 and 14.7 mm Hg, respectively (p < 0.001). Using the inflow port of the RNS for irrigation created a lower IRP (19.1 mm Hg) compared to the outflow port (32.7 mm Hg; p < 0.001). Addition of suction to all working scenarios significantly reduced IRP (p < 0.001). Insertion of instruments did not significantly alter IRP. Conclusion: In situations where the IRP should be low, removal of the RNS, irrigating through the inflow port, and frequent use of suction maintain the lowest pressures. If temporary increases in IRP are necessary to improve visualisation in the setting of bleeding, irrigating through the outflow port, minimising drainage and use of the RNS can be used to raise IRP.