<p>During ureteroscopy it is desirable to maintain renal pelvis pressure (P_RP) below 40 cmH₂O - the threshold for pyelovenous backflow - to decrease risk of infectious complications and postoperative pain. We sought to characterize P_RP in a silicone kidney ureter model when using a prototype fluid management system (pFMS) that adjusts flowrate based on pressure feedback. These results were compared to conventional pressurized irrigation at five outflow resistance (R_OUT) values. A LithoVue™ Elite ureteroscope was inserted into a silicone kidney ureter model with its tip in the renal pelvis. Irrigation was delivered from the pFMS with pressure limiter set to 40 cmH₂O or from conventional pressurized irrigation at 50, 75, 100, 125, or 150 cmH₂O. With pFMS irrigation, mean P_RP remained below 40 cmH₂O as R_OUT was incremented from 0.9 to 4.9 cmH₂O/(ml/min) respectively. With conventional pressurized irrigation, mean P_RP increased as irrigation pressure increased and as R_OUT increased. For example, when R_OUT was 2.0 cmH₂O/(ml/min), mean P_RP was 37 cmH₂O with both 125 cmH₂O conventional irrigation pressure and pFMS. However, with higher R_OUT values of 2.9, 4.0, and 4.9 cmH₂O/(ml/min), mean P_RP increased to 47, 57, and 60 cmH₂O respectively with 125 cmH₂O conventional irrigation pressure but was maintained below 40 cmH₂O with the pFMS. Automated adjustment of irrigation based on pressure feedback is an effective way to control P_RP and may reduce risk of infectious complications and postoperative pain.</p>