Purpose: We evaluated the pressure and flow relation of a newly developed continuous-flow ureterorenoscope (URS) in comparison with a common ureterorenoscope in an ex-vivo urinary tract model.
Materials and methods: Ureterorenoscopies were performed with the newly developed 10.5F continuous-flow URS with separate inflow and outflow channel and a conventional 10.5F URS with a combined inflow and outflow channel. The ex-vivo model consisted of complete urinary tracts of domestic pigs obtained freshly from the slaughterhouse. Both instruments were used in five urinary tracts, and six ureterorenoscopies were performed in each urinary tract. The pressure in the renal pelvis (RP) was measured during each procedure. Height of the irrigation solution above renal level and flow capacity were also documented.
Results: The conventional URS showed a correlation of intrapelvic pressure and the height of the irrigation solution above renal level rising from 20+/-3.7 cm H(2)O at a solution level of 20 cm to a plateau pressure of 40+/-3.3 cm H(2)O with a distinct renal influx at a level of 50 cm. The maximum flow capacity at a solution level of 20 cm was 0.2 mL/min rising to a flow capacity of 0.5 mL/min at 40 cm above renal level. The maximum flow capacity for the continuous-flow URS was about 100 times higher, rising from 20 mL/min at a solution level of 20 cm to 70 mL/min at 40 cm above renal level. The intrapelvic pressure was 15+/-2.1 cm H(2)O at a solution level of 20 cm and did not exceed the physiologic renal pressure of 20 cm H(2)O even if the irrigation solution was at a height of 100 cm above renal level.
Conclusion: The newly developed continuous-flow URS provides a 100 times higher flow capacity while simultaneously preserving the physiologic pressure in the RP compared with the conventional URS. These characteristics will improve visibility and reduce retrograde stone manipulation, operative time, and complications under clinical conditions.